Download 二）推荐摄入量（RNI）

NUTRITION
 Introduction of Nutrition
1.
Nutrition
•
Nutrition might be defined as the process whereby we obtain the essential
nutrients and use them to make many other substances our bodies need. This
process would include eating and digesting food and absorbing and using, or
metabolizing, the nutrients it contains.
2. NUTRIENTS
 Nutrients are the chemical components of food which perform nutritive functions:
• Fats
• Proteins
• Carbohydrates (sugars and starches)
• Minerals
• Vitamins
• Water
• ? Dietary fiber, Antioxidants
 Functions of Foods and Nutrients
• Provide energy for activities
• Build and maintain body tissue
• Regulate body processes
 The nutrients, their functions and representative foods
Carbohydrates Fats
Bread
Mutter
Potatoes
Cheese
Sugar
Olive
Biscuit
oil
Jam
Lard
Energy
Proteins Minerals
Meat Vegetable
Fish
fruit
Cheese
Eggs
milk
Water
Vitamins
Drinking Fruit
water
vegetables
Beverages
Fruit
vegetable
s
Growth
Control of body
and
process
3. Good Nutrition
repair
• Good nutrition implies that we
are obtaining from our food all of the essential
nutrients in the amounts needed to keep our bodies functioning and to
maintain optimum health.
•
•
•
A very simplified definition of good nutrition might be “eating the right
foods in the right amounts.”
Some foods only provide several nutrients or just one nutrient, such as sucrose,
we call them non-full nutrient food.
Some particularly valuable foods, such as milk, contain such a variety of
nutrients that they can fulfill all the functions of food, we call them
completely-valuable- food (全价食品).
Part 1
Gastrointestinal Tract, Digestion and Absorption
1．Digestion
• Digestion: The process by which food is broken down into absorbable units.
To take apart.
• GI Tract: Gastrointestinal: Stomach / intestines
2. Anatomy
1). Mouth - chews and mixes food, salivary glands secrete saliva with
starch-digesting enzymes
• Epiglottis (会厌)– protects airway
Trachea(气管)– passage for air to the lungs
2). Esophagus(食道)– passes food from mouth to stomach
• Cardiac sphincter(贲门括约肌)– allows passage from esophagus to stomach;
prevents backflow .
Food passes as a BOLUS(小而圆的物块) to stomach
3). Stomach – adds acid, enzymes, fluid. Churns, mixes, grinds food to a
liquid mass.
• 1) 3 muscle layers (peristalsis 蠕动).
• 2) mixed with gastic juice.
• 3) chief gland - pepsinogen released
• 4) Perietal - release HCl / reacts with pepsinogin to form pepsin.
• 5) Mucus protects stomach cells.
• 6) Water, salts, alcohol and sugar diffuse into the blood.
• Pyloric sphincter(幽门括约肌)– allows passage to small intestine; prevents
backflow
Food passes as CHYME (食糜) to duodenum
4). Small Intestine – secretes enzymes that digest all energy-yielding nutrients to
smaller particles. Cells of wall absorb nutrients into blood and lymph.
Duodenum, Jejunum, Ileum
(1) Duodenum
•
liver deposits bile,
Pancreas deposits insulin
• Sodium bicarbonate secreted by duodenum to conteract HCl from stomach
• Walls covered by villus
• Fats absorbed into the lymph system
• Minerals, Vitamines, Sugar and Amino Acids to blood stream
• Portal vein - nutrient filled blood sent to the liver
• Liver role is detoxification and storage of fat
(2) Jejunum: considered to be roughly 40% of the small gut in man, but closer to
90% in animals.
(3) Ileum empties into the large intestine; considered to be about 60% of the
intestine in man, but veterinary anatomists usually refer to it as being only the
short terminal section of the small intestine.
•
All of this absorption and much of the enzymatic digestion takes place on
the surface of small intestinal epithelial cells, and to accommodate these
processes, a huge mucosal surface area is required.
•
the absorptive surface area of the small intestine is roughly 250 square
meters .
Why?
• Mucosal folds
•
Villi: are covered with epithelial cells.
• Microvilli: the lumenal (内腔的) plasma membrane of absorptive epithelial
cells is studded （镶嵌）with densely-packed microvilli.
The microvillus border of intestinal epithelial cells is referred to as the "brush border."
5). Large Intestine (colon)
• 1) reabsorbs water and minerals.
• 2) Passes waste (fiber, bacteria, unabsorbed nutrients) along with water to
rectum
• 3) bacteria produce vitamine K ( used in blood clotting) and certain B
vitamins.
• 4）Digestion of carbohydrates not digested in the small intestine by the
microbial flora of the large intestine .
6). Rectum（直肠）– stores water prior to elimination
7). Anus（肛门）– holds rectum closed
This epithelial cell sheet is distinctly different in different regions of the tract.
3. Organs involved
• Liver – makes bile and is the first to receive nutrients from the intestines
• Gallbladder – stores and concentrates bile: excretes bile into the duodenum
when fat is present.
• Pancreas – Important roles as both an endocrine and exocrine organ provides a potent mixture of digestive enzymes to the small intestine which
are critical for digestion of fats, carbohydrates and protein.
• Appendix （阑尾）– a narrow blind sac extending from the beginning of the
colon that stores lymph cells appendix
4. Muscular actions:
1). Peristalsis （蠕动）: wavelike contractions of the GI tract that push contents
along
2). Stomach action: churns （搅拌 ）by muscular contractions
3). Segmentation （分割）: periodic squeezing or partitioning of the intestine at
intervals by circular muscles
4. Sphincter （括约肌） contractions
5. Digestive glands: Digestive Enzymes/Juices
 Salivary Glands (in mouth): secrete saliva (secretes carbohydrase enzyme to
act on carbohydrates)
 Gastric Glands (stomach): secrete gastric juice; hydrolysis of proteins
Water, enzymes, and hydrochloric acid
Hydrochloric acid (HCl) – very strong acid – stomach protected by mucus
 Pancreas-Intestinal: Pancreatic Juices and Intestinal Enzymes
• Digestion of Carbohydrates, Protein, Fat
 Liver-Gallbladder-small intestine: Bile
• Emulsifies fat: into a suspension
1) Salivary Glands
• parotid glands (腮腺): produce a serous, watery secretion
• submaxillary (mandibular) glands(下颚腺): produce a mixed serous and
mucous secretion
• sublingual glands (舌下腺): secrete a saliva that is predominantly mucous in
character
• The basis for different glands secreting saliva of differing composition can be
seen by examining salivary glands histologically. Two basic types of acinar
(腺泡的) epithelial cells exist:
• serous cells (浆液细胞) :which secrete a watery fluid, essentially devoid of
mucus (粘液).
• mucous cells, which produce a very mucus-rich secretion
• Acini (腺泡) in the parotid glands are almost exclusively of the serous type,
while those in the sublingual glands are predominantly mucous cells. In the
submaxillary glands, it is common to observe acini composed of both serous
and mucous epithelial cells.
Functions of Saliva
•
Lubrication(润滑油) and binding: the mucus in saliva is extremely effective in
binding masticated food into a slippery bolus
•
Solubilizes dry food: in order to be tasted, the molecules in food must be
solubilized.
•
Oral hygiene: The oral cavity is almost constantly flushed with saliva, which
floats away food debris and keeps the mouth relatively clean.
•
Initiates starch digestion: in most species, the serous acinar cells secrete an
alpha-amylase which can begin to digest dietary starch into maltose.
•
Provides alkaline buffering and fluid: this is of great importance in ruminants,
which have non-secretory forestomachs.
•
Evaporative cooling: clearly of importance in dogs, which have very poorly
developed sweat glands - look at a dog panting after a long run and this
function will be clear.
2) Pancreas
•
Pancreatic juice is composed of two secretory products critical to proper
digestion: digestive enzymes and bicarbonate.
•
Digestive Enzymes : Proteases , Pancreatic Lipase , Amylase , Other
Pancreatic Enzymes (ribonuclease, deoxyribonuclease, gelatinase and elastase.
•
Bicarbonate and Water
6. Regulation and Absorption:
1). Homeostasis (稳衡态):
•
maintenance
of
constant
conditions
(chemistry,
temperature,
blood
pressure). Stomach pH 1.5-1.7
2). Hormones:
•
(1) Gastrin(胃泌激素): tells stomach to secret gastric juices
•
(2) Gastric-peptide: Produced in intestine; tells stomach to slow secretion of
gastric juices
•
Secretin 分 泌 素 : Produced in duodenum; tells pancreas to secrete
bicarbonate-rich pancreatic juice
•
(3) Cholecystokinin / CCK(缩胆囊素,缩胆囊肽, 肠促胰酶肽): Produced in
intestine; tells gallbladder to release bile
3). Nervous system
•
Secretion of saliva is under control of the autonomic nervous system, which
controls both the volume and type of saliva secreted. This is actually fairly
interesting: a dog fed dry dog food produces saliva that is predominantly
serous, while dogs on a meat diet secrete saliva with much more mucus.
Parasympathetic (副交感神经) stimulation from the brain, results in greatly
enhanced secretion, as well as increased blood flow to the salivary glands.
•
Potent stimuli for increased salivation include the presence of food or irritating
substances in the mouth, and thoughts of or the smell of food. Knowing that
salivation is controlled by the brain will also help explain why many psychic
(精神的) stimuli also induce excessive salivation
- for example, why
some dogs salivate all over the house when it's thundering
The Central Nervous System
•
the hypothalamus (视丘下部) was thought to be the key to control of food
intake.
•
Lateral(侧面的)hypothalamus (hunger center): animals with lesions in this
area become anorectic (厌食的 and lose weight.
•
Ventromedial (腹正中的) hypothalamus (satiety 过饱 center): animals with
lesions in this area overeat and become obese.
Part 2 Carbohydrates
1. What are carbohydrates?
are important to the body as sources of energy. They can be found in a wide range of plant and
animal food sources. In plants they are generally end products of photosynthesis - the
process in which plants convert carbon dioxide and water into simple sugars such as
glucose
6CO2＋12H2O→C6H12O6＋6O2＋6H2O
Glucose
Water appears on both sides of this equation because it has been shown that all the oxygen
evolved originates from the water．The oxygen atoms in the glucose and water molecules
on the right-hand side of the equation are those which were originally combined with
carbon in the carbon dioxide．
In food carbohydrates are important for:
Flavour - adds sweetness
Texture - particularly starches and gums
Preserving - jams, hams, intermediate moisture foods.
Color – caramelization （焦糖化)
2. Class of carbohydrates
Carbohydrates contain only the elements carbon, hydrogen and oxygen and have the general
empirical formula of Cx(H20)y. They may be classified as simple or complex.
Simple Carbohydrates (Mono- and Disaccharides)
Monosaccharides are sugars containing a single ring:
Pentoses - xylose, ribose, arabinose
Hexoses - glucose (blood sugar), galactose, fructose (fruit sugar), mannose
1) Monosaccharides
The building blocks of carbohydrates are the simple 5-carbon rings (pentoses) and 6-carbon
ring (hexoses) such as glucose (C6H12O6)
A. D-glucose，dextrose or grape sugar
D-Glucose is found in grapes（up to seven per cent）and other sweet fruits，onions（about two
per cent）and tomatoes（about one per cent）also contain glucose，but honey，which
contains about 31 per cent，is the richest source of the sugar．
In animals it is produced during digestion of starch and other carbohydrates and it is a normal
component of the blood of living animals．Human blood has about 80—120mg／100ml
it is the only sugar which plays a significant part in human metabolism．
Glucose is a white solid；like all sugars it is sweet-tasting but it is less sweet than sucrose．
B. D-fructose， laevulose(左旋糖) or fruit sugar
The sugar fructose is found with glucose in honey， which contains about 35percent， and in
sweet fruit juices .
Fructose is about twice as sweet as sucrose—ordinary sugar—but it has the same energy
value， about 17KJ/g.
Fructose can thus be used by sweet-toothed slimmers as part of a calorie controlled diet.
Fructose can also be used as a sweetener by sufferers from the disease diabetes mellitus.
Unlike glucose and sucrose it does not require the hormone insulin for its utilization by
the body.
2) Disaccharides
are compounds that contain a bond between carbon (1) of one sugar and a hydroxyl group at
any position on the other sugar:
lactose (milk sugar), maltose, sucrose (common sugar)
A. Sucrose，cane sugar or beet sugar
the sucrose molecule must contain one glucose unit combined with one fructose unit．The
fructose unit in sucrose does not have a six-membered ring but a five-membered ring .
Sucrose (C12H22O11)
It is a white crystalline solid which dissolves in water to give a dextrorotatory solution.
Fructose is more strongly laevorotatory than glucose is dextrorotatory， so the mixture of
glucose and fructose is laevorotatory.
Sucrose is widely distributed in the vegetable kingdom in many fruits，grasses and roots and
in the sap of certain trees such as sugarcane (tropical) and sugar beets (temperate)
It is produced and consumed in far larger quantities than any other sugar．Over two million
tons of sucrose are used annually in USA（which is roughly 41 kg per person per year）.
B. Maltose or malt sugar
The sugar maltose is obtained when starchy materials are hydrolysed by the enzyme
diastase．Maltose can be further hydrolysed by the enzyme maltase or by heating with
dilute acid．
maltose contains two connected D-glucose units．
C. Lactose or milk sugar
Lactose is a white solid which is somewhat gritty in appearance．It occurs in the milk of all
animals：cow’s milk contains about 4-5 per cent and human milk 6-8 per cent．
A lactose molecule consists of one glucose and one galactose linked together．
Sweetness and sweteners
Why is sugar sweet？A simple question but，the answer is complex. It is even difficult to say
with any degree of precision what we mean by sweetness.
Although it is difficult to define sweetness and impossible to measure it in any absolute way,
it is possible to compare the relative sweetness of different substances.
3) Complex Carbohydrates (Polysaccharides)
are made up of three or more simple sugars linked together:
dextrin, gum, glycogen, pectin, starch
Polysaccharides are carbohydrates of high molecular weight which differ from the sugars in
being non- crystalline，generally insoluble in water and tasteless.
A polysaccharide is built up from a large number of connected monosaccharide units which
may be alike or different. As in the case of disaccharides，one molecule of water is lost in
the union between one monosaccharide molecule and the next. The polysaccharides are
all built up from monosaccharides containing six carbon atoms and are best formulated
（C6H12O6）n. The value of n varies，but in most cases is quite large.
Hydrolysis breaks down a polysaccharide molecule into smaller portions containing various
numbers of monosaccharide units and may ， if sufficiently drastic ， convert the
polysaccharide completely to monosaccharide：
（C6H10O5）n＋nH2O→nC6H12O6
(1) Starch
The glucose units in starch are the α- isomer.
is one of the most common complex carbohydrates, the energy storage compound in plants,
is easily digested by humans and animals.
It is the primary storage form of glucose in plants and is contained in high amounts in
potatoes, corn and tropical roots such as cassava (木薯).
Starches are formed as linked chains of glucose units. Starches such as amylose (an important
plant starch) are single chains while others such as amylopectin are branched chains.
Amylose (直链淀粉) and amylopectin （支链淀粉）
Amylose
Amylopectin
1. Amylose is responsible for the blue colour
produced when starch reacts with iodine.
Amylopectin ， on the other hand ， gives a
reddish- brown colour with iodine
2. The enzyme β- amylase，which is present in
only about half of it is converted into maltose
cereals，hydrolyses amylose almost completely
to maltose.
by β- amylase，the residue being referred to as a
dextrin.
3. The molecular weight of amylose varies from 3. the molecule is larger and may contain
about 10,000 to about 50,000 and this several million glucose units. there are a large
corresponds to 70-350 glucose units.
numbers of these chains each containing 20302 glucose units .
4. The glucose units are connected in a α- l-4
manner to form a chain
4. The glucose units are connected in a α- l-4
manner to form a straight chain, but at the
branch, it is α- l-6 manner.
amylase
amylopectin
Amylose can be separated from amylopectin by formation of an insoluble complex with a
suitable liquid such as butyl alcohol.
(2) Pectin
Pectin is the name given to a mixture of polysaccharides found in sol fruits and in the cell
walls of all plants.
Concentrated pectin extract can be bought for use in Jam making.
Pectin is present in unripe fruits and vegetables mainly in the form of its precursor
protopectin. This is a water- insoluble compound in which most of the carboxyl groups
are esterified. Protopectin is responsible for the hard texture of unripe fruits and
vegetables：during ripening enzymes present in the plant convert it into pectin.
Pectin from various sources differs somewhat in composition and hence it is not possible to
specify its structure too precisely. However all pectins consist essentially of the
polysaccharide methyl pectate which has long chain- like molecules of several hundred
connected units of α- D- galacturonic acid—an acid derived from the monosaccharide
galactose. Some of the acid groups have been esterified and converted from free carboxyl
（-COOH）groups to the methyl ester （-COOCH3）
(3) Glycogen
The polysaccharide glycogen acts as a reserve carbohydrate for man and other animals.
Because its function in man parallels that of starch in plants it is sometimes referred to as
animal starch. It is a very large molecule consisting of branched chains of α- D- glucose
units and its structure is very similar to that of amylopectin but chain branching occurs，
on the average，at about every 18-20 glucose units（compared with about 20-30 in
amylopectin）.
Glycogen is present in man and other animals in tie muscles and in the liver；There may be
several kilograms present in the body of a large animal such as a cow. Despite this，
however，glycogen is not a normal constituent of the diet because it is converted into
lactic acid after an animal has been killed.
(4) Fibres
Plant constituents resistant to digestion by secretions of the human gastrointestinal tract make
up the compounds known collectively as fiber. While they are not broken down by the
digestive juices of humans, some fibers may be absorbed to some extent, because they are
partially digested by intestinal bacteria.
These compounds often form the structural components of plant cells and are fibrous in
nature.
Fibres resist rapid digestion in the intestinal tract of humans but are readily used by ruminant
animals.
Cellulose: Cellulose (wood fibre) is the primary component of plant cell walls.
Cellulose can be hydrolysed by heating it with hydrochloric or sulphuric acid. The only
monosaccharide obtained in this process is D- glucose and it has been shown that the
cellulose molecule consists of a large number of β- D- glucose molecules connected
together at carbon atoms 1 and 4 to form very large chain .
Hemicellulose: The main component of cereal fibre. Hemicellulose is common in fruits and
vegetables.
Gums and Mucilages – soluble fiber
Gums are used as additives
Mucilages (guar, carrageenan黏液, 胶水) used as food stabilizers
Lignin – nonpolysaccharide fiber – insoluble fiber
Found in the woody parts of vegetables: carrots, strawberry seeds
Soluble fibres: Soluble fibre includes gums, mucilages (黏液质) and most pectins. Higher
concentrations of soluble fibres are found in fruits, oats, barley and legumes. Soluble
fibres are very good for health. They generally slow the emptying of the stomach, slow
glucose absorption and aid in lowering blood cholesterol.
Insoluble fibres: Insoluble fibres include cellulose, most hemicelluloses and lignin. Insoluble
fibres are high in vegetables, wheat and cereals. Insoluble fibres increase fecal weight,
slow starch breakdown and delay glucose absorption into the blood.
Dietary fibre: Dietary fibre refers to the total amount of naturally occurring materials in
foods, mostly plants, that is not digested. Dietary fibre is the non digestible form of
carbohydrate that is of nutritional importance in gastrointestinal disease.
Forms of carbohydrates in human diet
Class
Type
Monosacch-
Glucose, fructose, galactose
Yes
Yes
Yes
disaccharides
Sucrose, lactose, maltose
Yes
Yes
Yes
Dextrins, starch
Gums, mucilages
Algal polysaccharides
charide
Cell walls
Pectins
s
Hemicellulose
Cellulose
Lignin (no a carbohydrate)
Animal sources Glycogen
Yes
No
No
No
No
No
No
Yes
No
No
No
No
No
No
No
No
No
Yes
No
Yes
No
No
No
No
Plant sources
polysac Cell contents
Digested by
human
Sweet
taste
Water
soluble?
3. Digestion, absorption, and Metabolism of carbohydrates
Mouth
-Salivary glands secret salivary amylase into mouth
-Amylase breaks starch into small polysaccharides and maltose
Stomach
-Stomach acid inactivates salivary amylase
-Some starch is broken down in stomach
-No carbohydrate digesting enzymes
-Fiber stays in stomach longer and delays gastric emptying ‘full feeling’ (not digested)
Small intestine
Pancreas produces and releases pancreatic amylase into small intestine through pancreatic
duct: breaks down polysaccharides to smaller chains and disaccharides
-Disaccharides are broken down on outer membranes of intestinal cells by enzymes:
Maltase – breaks maltose: glucose/glucose
Sucrase – breaks sucrose: fructose/glucose
Lactase – breaks lactose: galactose/glucose
-Monosaccharides absorbed into intestinal cells
-Fiber not digested: delays absorption of other nutrients
The digestion of carbohydrate
Polysaccharides and oligosaccharides must be hydrolyzed to their component
monosaccharides before being absorbed. The digestion of starch begins with salivary
amylase, but this activity is much less important than that of pancreatic amylase in the
small intestine
Amylase hydrolyzes starch, with the primary end products being maltose, maltotriose, and a
-dextrins, although some glucose is also produced. The products of a -amylase digestion
are hydrolyzed into their component monosaccharides by enzymes expressed on the
brash border of the small intestinal cells, the most important of which are maltase,
sucrase, isomaltase and lactase
Carbohydrate absorption
Fructose:
absorbed passively down a concentration gradient
binds to a specific carrier protein in the apical cell membrane
either:
(1) diffuses passively out of cells and into capillaries
(2) forms lactate which then diffuses into portal blood
The absorption of glucose
1 absorbed mainly in jejunu（空肠）by active process
2 enters via a co-transporter protein on the apical side of the enterocyte (肠上皮细胞)
3 co-transporter requires presence of sodium ions
4 sodium ions pass down electrochemical gradient into cell to replace sodium ions which are
actively being transported out of cell on basolateral（底外侧的）membrane by Na+/K+
ATPase pump
5 glucose diffuses out of cell into
intercellular space and from there to local capillaries
6 chloride ions and water accompany the movement of sodium and glucose; they may travel
through the cell or through the intercellular space
Carbohydrate (CHO) Absorption
Large intestine
§-Bacteria enzymes digest some fiber
§-Ferments starch/fiber: creates water, gas, short chain fatty acids. (fatty acids
absorbed in colon)
§-Fiber attracts H2O,
promotes bowel movements, binds bile, cholesterol, and
some minerals
Lactose Intolerance
§Occurrence: about 70% of world population
§Lowest ethnic group: Northern Europeans
§Highest: Native North Americans, Southeast Asians.
§Why it happens:
§Lactase activity decreases dramatically after infanthood, resulting in an inability to digest
lactose.
§Symptoms:
Bloating, abdominal discomfort, diarrhea, nausea(恶心, 作呕), and gas.
§Dietary modifications:
§-Avoidance (with proper planning)
§-Eat fermented products (yogurt, acidophilus milk) where bacteria has already digested
much of the lactose
§-Eat aged cheese
§-Take enzyme tablets or add enzymes to products
Functions of carbohydrates
§1) Supply energy:
Carbohydrates provide 4 kcal/g, it is very important energy source for human and
animal.
§2) Carbohydrates are also an essential source of energy for the central nervous
system. Approximately one-fifth of the energy requirement of our basal metabolic rate
is for brain function, and only glucose, not fat, is required.
After meal rich in carbohydrates there is an increase in the rate at which the brain
synthesizes serotonin(血液中的复合胺), serotonin is one of sixe compounds, called
neurotransmitters (神经传递素).
§3) Spare protein
This means that when carbohydrates are plentiful in the diet, we will use them as a
source of energy instead of protein, thereby making the protein available for building
and repairing body tissue, it is much more efficient and less costly to use
carbohydrates for energy than use protein.
§4) help make Nonessential amino Acids.
Carbohydrates aid in the manufacture of certain nonessential amino acids when
they are in short supply.
§5) Storage Energy: glycogen is one energy storing in liver. Thought it is not so
much, but it is very important in provide energy to the body.
§6) Structural components: Carbohydrates and proteins can combine to form
several compounds that have important functions in the body, for example, serving as
lubricants (滑润剂) for joints and as the component of nail, bone, cartilage (软骨),
and skin.
Effects of carbohydrates to body
§Glucose is the primary energy source for the brain and nerves. Proteins may be
converted into glucose (i.e. energy), but inefficiently. The use of protein for energy
wastes this valuable resource which can be used for muscle building and growth.
§Rapidly digested carbohydrates can cause a major increase in insulin. Insulin is
designed to remove glucose from the blood for storage. The disease Diabetes mellitus
occurs in humans who can not produce enough insulin to remove the excess glucose.
The glucose is then excreted. A test for Diabetes looks for glucose in the urine.
Slowly digested carbohydrates can decrease the chance of excessive fat storage.
There are claims that dietary fibre reduces colon cancer.
After glycogen storage is filled, excess carbohydrate is stored as fat.
Too much sucrose and lack of dental hygiene usually results in dental decay.
§Some humans lack the enzyme lactase which digests lactose, the sugar in milk. The
lactose then passes from the stomach to the gut where bacteria use the sugar and
produce gas resulting in painful stomach cramps.
6. Physical and chemical properties of DF§1.the water-binding capacity
of fibers: prevent constipation.
§2. The minerals-binding capacity such as phytic acid: decrease the minerals’
absorption.
§3. The capacity of binding organic and toxic substances.-preventive factor in cancer
of the colon.
§4. No digested by endo-enzymes such as amylase
7. The function of dietary fibre
1) On the intestine itself
1 Increased small intestine wall thickness (mucosa)
2 Increased small intestine weight
3 Changes in the villi
(1) Increased number of neutrophils
(2) Increase mitosis (cell division rate)
(3) Increased number of crypt (隐蔽性)cells
(4)Blunting(钝化) and disarray of villi (soluble fibre)
4 Thinning of colon(结肠) wall
2) On intestinal contents
1 Alter the transit time of food through the intestinal tract. Generally fibre increases
segmental contractions. This slows gastric emptying, slows transit through the colon,
but can have a varying effect on small intestine transit time.
2 Increased secretion（分泌） of enzymes
3 Altered pH of intestinal contents (chyme)
3) On faecal production §More faecal waste material
§Faecal bulking(膨胀)due to retention of water
§The faecal stool is softer and easier to pass
§More gas production (due to increased fermentation)
§Increased faecal nitrogen and fat excretion
§Changes bacterial content of large intestine
4) Metabolic effects
1.Altered glucose tolerance (absorption)
2.Reduced post-prandial insulin secretion
3.Reduced triglyceride (甘油三酸脂) and fatty acid synthesis
4.Reduced plasma (血浆) and liver fat concentrations
Dietary Fiber and Health
A. Hyperlipidemia and CHD-coronary heart disease
§1. epidemiological evidence suggest that complete vegetarians have significantly lower serum
cholesterol and the highest intake of crude fiber§2. developed countries with low fiber intake
have high CHD and serum cholesterol levels.§3. epidemiological evidence weak as there is
no control of SFA's or total kcals§4. Intervention (干涉) studies show that water-soluble
fibers lower cholesterol - often non physiologic levels given (twice the recommended
10g/1000 kcals)§5. mechanism of action not know but believed to be associated with:§a.
decrease absorption of SFA and cholesterol§b. alteration of intestinal synthesis of cholesterol
B. Colon Cancer§1. initial epidemiological studies suggest a link between crude
fiber intake and colon cancer§2. case-control studies have been inconclusive§3.
mechanism of action:
§a. reduction in transit time of the large bowel
§ b.
bulking agent
§c. binds bile salts
C. CHO and Non-Insulin Dependent Diabetes Mellitus (NIDDM)
§A. Characteristics§1. insulin resistance rather than insulin deficiency§2. occurs
almost exclusively in the population above 45 years of age§3. can be controlled by
diet B. Evidence suggesting diet rather than aging as the primary cause of NIDDM rodent studies§1. several investigations have reported that high fat, high sucrose
diets fed to rodent induce insulin resistance§a. not clear if it is obesity or diet
macronutrient composition§b. not clear if sedentary (久坐的) life style of rodent
cause obesity that leads to insulin resistance2. study designed to evaluate these
possibilities - rats
Group
Body Weight
Degree of
Resistance
Obesity diet, sedentary
Highest
Highest
Non-Obesity Diet,
Sedentary
Next Highest
Next Highest
Obesity Diet, Exercise
Next Highest
Next Highest
Non-Obesity Diet, Exercise
Lowest
Lowest
Pair Fed, Sedentary
Lowest
Lowest
Insulin
C. Evidence suggesting diet rather than aging as the primary cause of NIDDM humans§1. previously sedentary, obese individual with NIDDM placed on kcal
reduced diet and exercise§2. NIDDM reversed with reduction in weight§3. 20 30% did not respond to weight reduction -- thought to be genetic
§§*Why does obesity in older, not younger, people causes NIDDM?* D. Role of
specific saccharides in the cause and treatment of NIDDM1. sucrose§a. high
sucrose diet previously reported to induce insulin resistance in rats§b. poor control
for obesity§c. more recent data demonstrate no effect.2. fructose§a. since fructose
does not cause an increase in serum glucose, most physician suggest that substitution
of fructose for sucrose is OK§b. other suggest that fructose induces hyperlipidemia,
and thus may be bad for genetic-related NIDDM - Syndrome X (hyperlipidemia,
hypertension, insulin resistance
9. Recommendation§60-70% of total diet energy comes from carbohydrates is
a good proportion for health.
§Chinese taking in carbohydrates is decreased,
Chronic diseases, such as coronal
heart disease, Diabetes, hyperlipidemia, hypertension, etc. are increased
10.The excessiveness of carbohydrate1).Converted to fat and stored
2).Increases body fat by suppressing fat oxidation
3).Can cause diabetes mellitus
4).Can cause high bloody grease The lack of carbohydrate§More protein
utilized as fuel source
§Endurance can be reduced up to 50% until body adapts
§Glycogen stores become depleted
§Ketosis: Break down of protein (muscle wasting) and incomplete combustion of
fats (ketone bodies )
§Body can adapt and convert dietary protein to carbohydrates via gluconeogenesis
（糖原重生）.12. Carbohydrate Sources§Carbohydrates derive from both
plant and animal sources. But plants are the ultimate producers of carbohydrates.
Utilizing the process of photosynthesis, they first synthesize simple sugars from
water and carbon dioxide using sunlight as the energy source. Next they then further
combine the sugars into complex carbohydrates.
§Starch is used for future energy needs and cellulose and hemicellulose for cell wall
structures. § Glucose: Abundant in carbohydrate-rich foods: grains, fruits,
vegetables, milk .
§Fructose: Abundant in fruit, honey, and saps
§Galactose: Rarely found outside of lactose.
§Maltose: Produced during starch digestion in the body
§Sucrose: Table sugar, fruit, vegetables, and grains
§Lactose: Milk, dairy products .
§Glycogen: Found in liver and muscle tissue
Not a significant food source of carbohydrate
§Starch: Found in grains (wheat, rice), legumes, and tubers (potatoes, yams, cassava)
Fibers Sources§. Cellulose – insoluble fiber
§Primary constituent of plant cell walls
Found in all fruits, vegetables, legumes
2. Hemicelluloses – soluble and insoluble fiber
§Primary constituent of cereal fibers
§3. Pectins – soluble fiber
§Found in vegetables and fruits (especially citrus, apples)
Used to thicken jelly, controls texture and consistency
§4. Gums and Mucilages – soluble fiber
§Gums are used as additives
Mucilages (guar, carrageenan) used as food stabilizers
§5. Lignin – nonpolysaccharide fiber – insoluble fiber
§Found in the woody parts of vegetables: carrots, strawberry seeds
Good Sources of Starch §Breads, both whole-grain and white
§Breakfast cereals, cooked and ready-to-eat
§Flours, whole-grain and white
§Pastas, such as macaroni and spaghetti
§Barley and rice
§Legumes - dried peas, beans and lentils
§Starchy vegetables, such as potatoes, butter beans, corn, potatoes, sweet peas, lima
beans, and navy beans
Good Sources of Fiber §Whole-grain breads, other grain bakery products
§Whole-grain cereals, cooked and ready-to-eat
§Legumes - kidney beans, lima beans, navy beans, and split peas
§Fruits, especially the skins and edible seeds
§Nuts and seeds
Part 3.
Proteins and Amino Acids
1. Amino Acids
•
•
The building blocks of protein
Structure: every amino acid contains an amino group,
and acid group, a hydrogen atom, and a distinctive side
group all attached to a central carbon atom.
• In nature, all amino acids are L-amino acids. Drawing the structures as Fischer
projections, this corresponds to placing the –COOH group at the top and the –NH2 group
to the left.
• Amino acids have this basic structure, but the side chain, R maybe any of 20 different
• groups
Amino acids have the properties of both acids and bases and this enables them to undergo an
intramolecular acid-base reaction. Amino acids exist primarily in the form of a dipolar zwitterion
(两性离子)
1). Classes of Amino Acids according to their chemical properties
(1）Aliphatic (脂肪族的) amino acids:
Glycine (Gly 甘氨酸), Alanine (Ala 丙氨酸), Valine (Val 缬氨酸), Leucine (Leu 亮氨酸),
Isoleucine (Ile 异亮氨酸)
(2) Amino Acids with hydroxyl or Sulphur containing Side chains:
Serine (Ser 丝氨酸), Cysteine(Cys 半胱氨酸), Threonine (Thr 苏氨酸), Methionine (Met)
(3) Aromatic amino acids:
Phenylalanine (Phe 苯丙氨酸), Tyrosine (Tyr 酪氨酸), Tryptophan (Trp 色氨酸)
(4) Acidic Amino Acids and their Amides:
Aspartic Acid (Asp 天冬氨酸), Glutamic Acid (Glu), Asparagine (Asn 天冬酰胺酸), Glutamine
(Gln 谷氨酸盐)
(5) Basic Amino Acids:
Histidine (His 组氨酸), Lysine (Lys 赖氨酸), Arginine (Arg 精氨酸)
(6) Cyclic Amino Acid: Proline
(Pro 脯氨酸)
2). Classes According to Origin
(1) Non-essential amino acids: the body can synthesize more than half of the amino acids from
nitrogen, carbohydrates, and fat , must not obtain them from food.
(2) Conditionally-essential amino acids: some normally non-essential amino acids become
essential for people with certain conditions (ie: tyrosine for phenylketonuria 苯丙酮酸尿症,
and glutamine for some liver diseases).
Cystine and tyrosine
(3) Essential amino acids (EAAs)
Essential amino acids (EAAs): There are nine essential amino acids that the body cannot
make in sufficient quantities and, therefore, must obtain them from food.
EAAs: Tryptophan, Lysine, Methionine, Phenylalanine, Threonine, Valine, Leucine & Isoleucine .
The human infant also requires a dietary supply of histidine.
3) Functions of Amino Acids
AMINO ACIDS are the "building Blocks" of the body, they build cells and repairing tissue.
They form antibodies to combat invading bacteria & viruses;
They are part of the enzyme & hormonal system;
They build nucleoproteins (RNA & DNA);
They carry oxygen throughout the body and participate in muscle activity.
A . EAA
(1) TRYPTOPHAN (EAA)
• A natural relaxant, helps alleviate insomnia (减轻失眠症) by inducing normal sleep;
reduces anxiety & depression;
• helps in the treatment of migraine headaches（偏头痛）;
• helps the immune system;
• helps reduce the risk of artery & heart spasms （痉挛）;
• works with Lysine in reducing cholesterol levels.
(2) LYSINE (Essential Amino Acid)
• Insures the adequate absorption of calcium;
• helps form collagen（胶原质）( which makes up bone cartilage（软骨 ） & connective
tissues);
• aids in the production of antibodies, hormones & enzymes.
• Recent studies have shown that Lysine may be effective against herpes （疱疹）by
improving the balance of nutrients that reduce viral growth.
• A deficiency may result in tiredness, inability to concentrate, irritability, bloodshot eyes,
retarded growth, hair loss ,anemia & reproductive problems
(3) METHIONINE (EAA)
• Is a principle supplier of sulfur which prevents disorders of the hair, skin and nails;
• helps lower cholesterol levels by increasing the liver's production of lecithin;
• reduces liver fat and protects the kidneys;
• a natural chelating agent for heavy metals;
• regulates the formation of ammonia and creates ammonia-free urine which reduces bladder
irritation;
• influences hair follicles and promotes hair growth.
(4) PHENYLALANINE (EAA)
• Used by the brain to produce Norepinephrine（去甲肾上腺素）, a chemical that transmits
signals between nerve cells and the brain;
• keeps you awake & alert;
• reduces hunger pains;
• functions as an antidepressant and helps improve memory.
(5) THREONINE (EAA)
• Is an important constituent of collagen, Elastin, and enamel protein;
• helps prevents fat build-up in the liver;
• helps the digestive and intestinal tracts function more smoothly; assists metabolism and
assimilation.
(6) VALINE (EAA)
• Promotes mental vigor, muscle coordination and calm emotions.
(7) LEUCINE & ISOLEUCINE (EAA)
• They provide ingredients for the manufacturing of other essential biochemical components
in the body, some of which are utilized for the production of energy,
• stimulants to the upper brain and helping you to be more alert.
B. Non- EAA
(1) ARGININE
• Studies have shown that it has improved immune responses to bacteria, viruses & tumor
cells;
• promotes wound healing and regeneration of the liver;
• causes the release of growth hormones; considered crucial for optimal muscle growth and
tissue
（2）TYROSINE
• Transmits nerve impulses to the brain;
• helps overcome depression; Improves memory; increases mental alertness;
• promotes the healthy functioning of the thyroid, adrenal and pituitary glands.
(3) GLYCINE
• Helps trigger（引发）the release of oxygen to the energy requiring cell-making process;
• Important in the manufacturing of hormones
• responsible for a strong immune system.
(4) SERINE
• A storage source of glucose by the liver and muscles;
• helps strengthen the immune system by providing antibodies;
• synthesizes fatty acid sheath（鞘）around nerve fibers .
(5) GLUTAMIC ACID
• Considered to be nature's "Brain food" by improving mental capacities;
•
helps speed the healing (康复) of ulcers (溃疡);
•
gives a "lift" from fatigue;
• helps control alcoholism, schizophrenia (精神分裂症) and the craving (渴望) for sugar.
(6) ASPARTIC ACID
• Aids in the expulsion of harmful ammonia from the body. When ammonia enters the
circulatory system it acts as a highly toxic substance which can be harmful to the central
nervous system.
• Recent studies have shown that Aspartic Acid may increase resistance to fatigue and
increase endurance.
(7) TAURINE(氨基乙磺酸,牛磺酸)
• Helps stabilize the excitability of membranes which is very important in the control of
epileptic(癫痫性的) seizures.
• Taurine and sulfur are considered to be factors necessary for the control of many
biochemical changes that take place in the aging process;
• aids in the clearing of free radical wastes.
(8) CYSTINE
• Functions as an antioxidant and is a powerful aid to the body in protecting against
radiation and pollution.
•
It can help slow down the aging process, deactivate free radicals, neutralize toxins;
•
•
aids in protein synthesis and presents cellular change.
It is necessary for the formation of the skin, which aids in the recovery from burns and
surgical operations. Hair and skin are made up 10-14% Cystine.
(9) HISTIDINE
• Is found abundantly in hemoglobin;
•
has been used in the treatment of rheumatoid arthritis (风湿性关节炎), allergic diseases,
ulcers & anemia.
•
A deficiency can cause poor hearing.
(10) PROLINE
• Is extremely important for the proper functioning of joints and tendons;
• also helps maintain and strengthen heart muscles.
(11) ALANINE
• Is an important source of energy for muscle tissue, the brain and central nervous system;
• strengthens the immune system by producing antibodies;
• helps in the metabolism of sugars and organic acids
2. Proteins
Amino acid chains: condensation reactions create bonds between amino acids to form a
peptide bond:
•
•
•
•
•
dipeptides: two amino acids bonded together
tripeptide: three amino acids bonded together
oligopeptide: 4-9 amino acids bonded together
polypeptide: 10 or more amino acids bonded together
Amino Acid Sequences: the specific order of amino acids in polypeptide chains varies
greatly
1) Protein Structures
Primary Structure of proteins is the sequence of amino acids.Twenty-two amino acids are
used in the chain structure of proteins. Amino acids can be linear or ring molecules but
all contain an amino (-NH2) and a carboxyl (-COOH) group.
Secondary Structure is the folding of the long thin chains of amino acids into structures such
as the alpha helix(螺旋), These structure stabilize the protein since other bonds form as
the amino acid chains wrap around (环绕的) each other.
a- helices
a-helices arise as a consequence of hydrogen bonding interactions between non-adjacent
backbone carbonyl and amide groups (usually separated by 4 groups), running parallel to
the axis of the helix.
Tertiary Structure is the shape of a large portion of the protein molecule which involves
additional folding of the helix for example creating
even more bonds and stability.
This shape arises as a consequence of stabilising
hydrophobic interactions, hydrogen bonds,
disulfide bridges, and often metal centres.
Quaternary Structure
Primary, secondary and tertiary structures involve
only a single protein chain. Quaternary structure involves how several polypeptide chains come
together and the resulting shapes and bonds.
Myoglobin, the compound which carries
oxygen in muscle tissue and is responsible
for the red colour of fresh meat, has a
quaternary structure .
the shape depends on the sequence of amino
acids, the bonds linking them, and the
interactions of the side chains with each other
with surrounding molecules .
STABILITY OF PROTEINS
• Van der Waals interactions
• Hydrogen bonding
• Electrostatic interactions
• Hydrophobic interactions
• Disulphide bridges
the chain folds so that electrically charged (hydrophilic) side chains are folded outwardly and the
neutral (hydrophobic) groups are folded inwardly for stability in bodily fluids
2) Protein Functions
• Form body tissue, such as muscle tissue, tendon(腱) structure
• Maintain water balance
• Maintain acid-base balance
• Supplying energy
• Functional substances, such as hormones, hemoglobin, carriers
(1) Form body tissue
• Building and repairing body tissue is the most important function of proteins. Proteins
form the basis of every body cell. Thus it is obvious that the greatest need for protein is
during periods when cells are growing rapidly: during infancy, childhood, adolescence,
and pregnancy.
• During lactation, a women needs extra protein to produce milk. Infants and children need
the most protein in proportion to the size.
• The lack of protein in early childhood can lead to the deficiency disease kwashiorkor (夸
休可尔症，恶性营养不良), and eventual death, Marasmus (消瘦)
Our bodies, once formed, are not static, but are constantly being degraded and rebuilt. The
turnover rate varies in different parts of the body. Some tissues, such as the lining of the intestine,
renews itself every one to three days. Blood cells regenerate every 120 days. Liver cells have a
high turnover rate too, but muscle renew themselves much more slowly, while the turnover of
brain cell is negligible. This degradation of body tissue is one source of protein that we can reuse.
(2 ) maintain water balance
Plasma proteins that are too large to pass through cell walls maintain the osmotic pressure
needed to draw fluid back out of cells (water which forms from the oxidation of glucose, for
example) and into the bloodstream. If Plasma protein levels is low, fluid may accumulate in
cells, and low-protein edema (浮肿)(swelling) results. Starving people, especially children, are
often seen to have this type of retention of extra water in their tissue.
(3) Maintain the acid- base balance
The pH of body tissue is just slightly alkaline (pH 7.4). Proteins are able to function as either
acids or alkalines to maintain this pH because they have amino groups that are alkaline and
carboxyl groups that are acidic. So they can unite with either acids or bases as needed to reduce
excess acidity or alkalinity in body fluids.
(4) Form functional substances
• In addition to forming major body tissues, proteins are also needed in smaller amounts to
make the enzymes and hormones that regulate all body processes, as well as the
antibodies that are needed to fight infections. When the protein intake is low, fewer
antibodies are produced, and a person is more vulnerable to attack by infectious
organisms.
• Tryptophan is a precursor of the B vitamin niacin, methionine can help reduce the need
for two other B vitamin.
• Transportation: transport lipids, vitamins, minerals, and oxygen
(5) Extra protein provides energy
• Any extra protein available in the body after its essential functions are satisfied is used as
a source of energy. The calorie yield of protein is similar to that of carbohydrate- 4 Kcal
per gram. If we are getting enough energy from other sources, the excess protein is
•
converted to fat for energy storage.
On the other hand, if we are not getting all the energy we need in our food from
carbohydrate and fat sources, then we will use protein in our food to meet our energy
needs, rather than our protein needs. If body fat stores are depleted and our diet lacks
sufficient energy, We will draw protein from our body tissue to supply energy, we will
draw protein from our body tissue to supply energy to keep our body processes
functioning.
3) Protein Digestion and Absorption
• Food proteins are digested by proteolytic enzymes in the gastrointestinal tract:
• First by pepsin, present in the gastric juice;
•
Then by proteases secreted by the pancreas and by the cells from the intestinal mucosa.
• Most of these enzymes catalyze the hydrolysis of specific peptide bonds.
(1) In the stomach
• Hydrochloric acid and pepsin and the protein-splitting enzyme protease attack specific
linkages on the ends of the protein chains, reducing them to shorter chains called
polypeptides and peptones (蛋白胨).
• Pepsin is present in the stomach in an inactive form, pepsinogen, which is converted to its
active form by hydrochloric acid.
(2) In the duodenum
• The acid is neutralized and the food mixture becomes slightly alkaline. Here the
pancreatic juice contains a strong proteolytic (蛋白水解的) enzyme , trypsin (胰岛素), or
pancreatic protease.
• Trypsin attacks the polypeptide chains selectively at the carboxyl groups. This reduces the
length of peptides to dipeptide and tripeptide chains.
• The carboxypeptidase (羧肽酶) chews at the carboxyl end of the peptide linkage.
• The aminopeptidase (氨基肽酶) acts on the amino group of the peptide linkage.
• Pentones are hydrolyzed by erepsin(肠肽酶) into dipeptides.
• Finally, the entire polypeptide or tripeptide chains are reduced to dipeptides.
• Dipeptidase cleave the linkage between the remaining two amino acids
(3) Amino acids absorption
• The amino acids may be absorbed either by active transport or by a simple diffusion
process across the intestinal wall and into the bloodstream.
• Free amino acids and small peptides are absorbed through the brush-border cells of the
intestinal mucosa.
• Specific absorption mechanisms are operative for neutral, acid, or basic amino acids and
for peptides.
• Most absorbed peptides are hydrolyzed within the intestinal cells. The absorbed amino
acids then pass into the portal vein for transport to the liver.
For 100g of food proteins ingested per day, only about 10g is eliminated in the feces, although an
additional 50-70g of “endogenous” proteins (about 1/3 of protein assimilated is from endogenous
source ) are secreted daily into the gastrointestinal tract. These endogenous proteins also are
secreted daily into the most part. This mechanism provides optimal amounts and proportions of
amino acids for the synthesis of body proteins.
(4) Allergic reaction
Some individuals are unable to digest proteins into their component amino acids. As a result,
larger protein fragments may get absorbed into the system and cause an allergic reaction.
This generally is the reason why some people are allergic to specific foods such as milk, egg, or
chocolate.
(5) Protein Anabolism and Catabolism
• Body proteins (10-12kg in a 70kg man) are continuously broken down into amino acids in
situ (catabolism) and must therefore be resynthesized in corresponding amounts
(anabolism). This “turnover” is rapid (several months) for muscular proteins and for
collagen from bone and connective tissues.
• Free amino acid “pools” present in the plasma and the tissues, and available
for protein synthesis, are therefore provided both from ingested food proteins and from
catabolized body proteins. Protein catabolism takes place primarily at the intracellular level, where
various proteases, known as cathepsins (组织蛋白酶), are located within the lysosomal (溶酶体)
organelles. It is believed that protein turnovers is necessary to enable the level of biologically
active proteins to adjust in accord with changing body needs.
Because there is no perfect time and/or space synchronization (同步) between protein
catabolism and anabolism, excess amino acids present at given times are degraded through the
carbohydrate pathways, with the production of energy. The nitrogen released is excreted into the
urine, mainly as urea.
3. Estimating Protein Requirements
1) Factors affecting protein requirements
1. Digestibility
2. Amounts and proportions of amino acids
3. Energy intake
a. insufficient calories from carbohydrate induces the oxidation of protein
b. excess kcal improves nitrogen retention
4. protein quality -- most important
2) Balance Studies, metabolic ward
1. measurement of intake vs. output
a. 90% of excretion in urine
b. 5% in feces (protein absorbed throughout intestine)
c. 5% sloughed off as dead skin cells (difficult to measure)
2. obligatory nitrogen loss,
a. the amount of nitrogen lost not excreted in the urine (balance studies)
b. the amount of nitrogen lost from all routes (factorial methods; see below)
3. procedure of balance studies
a. very low protein diet to the point where excretion exceeds intake, i.e. negative protein
balance
b. gradually increase protein intake until balance. That is, until intake equal output.
c. recommendations set at +2 SD
d. we do not have good measures for obligatory losses.
4. limitations of balance studies
a. limited number of subjects
b. protein quality may vary
c. age may play a factor; young and old
d. very expensive
3) Factorial Method
1. this method used where balance studies are dangerous or impractical.
a. lactation; b. pregnancy; c. small children
2. Equation:
Protein Requirement = obligatory nitrogen + growth factor + milk production x 1.3
a. obligatory nitrogen estimated from surface area; also a standard of 53 mg per day used
b. growth factor estimated from rate of growth
c. milk production: 750ml per day x 0.11 g protein
d. 1.3 is used as a error term (by convention only)
4. Protein Nutritive Value of Food
1) Factors Influencing Protein Value
The protein nutritive value of food corresponds to its ability to meet nitrogen and amino acids
requirements of the consumer, and to ensure proper growth and maintenance. This ability is a
function of several factors.
(1) Protein Content.
Staple (常用的) foods with protein contents below 3% do not meet the protein requirements of
humans even when ingested in amounts supplying more than the caloric requirements. This
probably explains why, in developing countries, protein-calorie malnutrition is much more
common than malnutrition attributable solely to protein deficiency.
(2) Protein Quality.
• The quality, value, or balance of a food protein depends on the kinds and amounts of amino
acids it contains, and represents.
• A balanced or high-quality protein contains essential amino acids in ratios commensurate
with human needs.
• Proteins of animal origin generally are of higher quality than those of plant origin.
• This can be determined by comparing the amino acid contents of various protein with the
FAO pattern (table). The FAO reference pattern was chosen to satisfy the requirements of
the young child.
• Cereal proteins are often low in lysine, and in some instances they lack tryptophan and
threonine.
• Oilseeds and nuts are often deficient in methionine and lysine, whereas legumes often lack
methionine.
• Those essential amino acids in greatest deficit with respect to requirements are designated
“limiting” amino acids.
• When the dietary pattern of amino acids differs greatly from the ideal pattern, this situation
is referred to as “amino acids imbalance”. It can lead to reduced efficiency of amino acids
utilization, depressed growth, increased susceptibility to diseases, and/or permanent
impairment of mental capabilities in children.
(3) Complementary action 互补作用
• Where a particular protein is deficient in an essential amino acid，the disadvantage may be
overcome simply by eating more of the protein in question.
• although a certain protein may be of low quality because it lacks a particular amino acid，if
it is eaten together with a second protein which lacks a different essential amino acid，the
mixture is of high biological value．Such amino acids are said to complement each
other．This principle is illustrated by a mixture of gelatin and bread．The limiting amino acid
of wheat is lysine whereas that of gelatin is tryptophan．As gelatin is relatively rich in lysine
the two complement each other．Examples of other complementary proteins are fish and
rice and maize and beans.
• even if each protein alone is of low quality. Thus, cereal proteins can be efficiently
complemented with small amounts of soy or milk proteins. It is called as “complementary
action”.
• But soy proteins are less efficiently complemented with small amounts of animal proteins.
• Improvement of essential amino acid balance, and of overall protein quality, also can be
achieved by supplementing the diet with free amino acids, or possibly with proteins to
which amino acids have been covalently (共同地) attached.
• Supplementation and complementation are widely used in animal feeding.
• Complementation widely occurs in the mixed diets of the Western world and in some other
countries.
• It is generally true that a diet in which 30-40% of the protein comes from animal sources
contain a proper balance of amino acids.
• FAO surveys of protein supplies in 1977 indicated that the mean daily availability of animal
and vegetable proteins was, respectively, 73 and 34g per person in the United States,
compared with 12 and 44g per person in developing countries.
• Attempts have been made to add lysine to cereal diets consumed by some human
populations of Africa and the Middle East. However, these attempts have not resulted in
physiological improvements, possibly because cereals alone met the protein requirements
（Amino acids can’t get balance?）
。
• Excessive supplementation may lead to “amino acid antagonism （拮抗）” or even toxicity.
Antagonism results in increased requirements for some amino acids because the dietary
level of another amino acid has been increased.
•
i.e, a leucine intake well in excess of requirement depresses tryptophan and isoleucine
utilization, and therefore increases the requirements of these two amino acids.
• Large excesses of methionine, cysteine, tyrosine, tryptophan, and histidine are known to
cause growth inhibition, reduced food intake, and certain pathological conditions in
animals.
(4) Amino Acid Availability
• not necessarily fully “available”, since digestion of the protein or absorption of the amino
acids may be incomplete. Amino acids from animal proteins are generally digested and
absorbed to an extend of 90%, whereas those from certain plant proteins may be digested
and absorbed to an extend of only 60-70%.
The lower utilization of certain proteins may be due to several factors:
(a) Proteins conformation: fibrous insoluble proteins are less readily attacked by proteases than
soluble globulins. However, protein denaturation by mild heating often enhances digestion.
(b) Binding of metals, lipids, nucleic acids, cellulose, or other polysaccharides to proteins may
partially impair digestion.
(c) The presence of antinutritional factors, such as trypsin and chymotrypsin (糜蛋白酶)
inhibitors, can impair digestion of proteins. Other inhibitions are able to impair amino acids
absorption.
(d) The size and the surface area of the ingested protein particles can influence digestibility. For
instance, fine milling of flours tends to improve the digestibility of cereal proteins.
(e) Processing at high temperatures, at alkaline pH, or in the presence of reducing (还原)
carbohydrates often decreases protein digestibility and the biological availability of several amino
acids, especially lysine.
(f) Biological differences exist among individuals, and this can influence their ability to digest and
absorb amino acids.
2 ) Determination of Protein Nutritive Value
Since proteins differ in nutritive value, evaluation of this aspect is useful
(a) to allow prediction of the amount of food protein, or mixture of food proteins;
(b) to allow the ranking of proteins as a function of their potential nutritive value;
(c) to allow the detection of nutritive changes food proteins may undergo during processing and
storage.
(1) Bioassays.
•
Biological assays are based on measurements of growth or nitrogen retention in
experimental animals, such as rats, or in humans, as function of protein intake.
• For reliable accuracy and meaningfulness of the data, several animals must be used per
test, and the result must be analyzed statistically.
• Test conditions also must be standardized. The protein level of the diet is generally kept
low (10% by weight) so that protein intake remains below requirements。
• The supply of energy and other nutrients must be adequate.
• Under these condition, growth is slow, the protein is efficiently utilized (little protein is
degraded to energy), and the experimental results emphasize differences in nutritive
values among proteins and reflect the maximum nutritive value of each protein tested.
• However, the test value obtained overstates (夸张) how the protein will perform under the
practical conditions of human consumption.
DIGESTIBILITY OF PROTEINS
•
•
While a great deal of research has been devoted to protein quality，little consideration has
been given to digestibility .As it is now believed that few diets provide insufficient
amounts of essential amino acids，except for infants and preschool children，more
attention needs to be given to digestibility．
It is evident from Table 8．8 that while animal proteins are highly digestible，plant
proteins may have a much lower rate of digestibility This factor needs to be taken into
account when considering protein requirements（see below）
．The digestibility of protein
foods is related to their content of dietary fibre which increases excretion of nitrogen In
faeces and hence reduces the apparent digestibility．
Relative digestibility of different foods（FAO／WHO，1985）
① Protein Efficiency Ratio (PER)
-- is a measure of the amount of weight gain per given protein intake
(weight gain g/ protein intake g)
1. can be used only during growth
2. the greater the slope is, the better the PER is
3. poor initial PER can be overcome by increase protein
a. catch up growth
b. must start during exponential (指数的) growth phase
5. when doing the studies, must be sure that there are no other deficiencies
6. Is bigger better?
a. large babies are healthier
b. low birth weigh babies have high mortality rate
c. caloric restriction model
d. studies are done over a short term
The protein efficiency ratio (PER) is the weight (grams) gained by rats per gram protein
consumed. Because this value is easy to determine, it is the most commonly used method.
Inaccuracies arise because the result obtained depends on the amount of protein actually
consumed by the rats, and because rats grow faster than children. Thus protein quality is
understated.
② Net protein ratio (NPR)
When the weight loss of a group of rats fed a protein-free diet is included in the calculation,
protein can be evaluated for their ability to support maintenance as well as growth, and a value
known as net protein ratio (NPR) is obtained.
These methods can be improve if
(a) values are determined at several different level of protein in the diet, a plot (图) of change in
weight versus protein intake is prepared, and the slope of this plot is measured on the straight
line portion of the response curve (multipoint slope ratio), and
(b) the values obtained with the test protein are expressed as a percentage of those obtained with
egg or milk protein (relative NPR). When both modifications are adopted, the protein values
obtained (relative protein values, RPV) are more accurate and more useful in practical
situations.
Another approach involves measuring the uptake of nitrogen and loss of nitrogen in the feces
and urine. By this means, it is then possible to calculate the absorbed percent of ingested
nitrogen (coefficient of protein digestibility), and the retained percentage of absorbed nitrogen
in the body (biological value). The biological value reflects the balance of essential amino acids
in the absorbed protein digest.
③ Biological Value (BV)
1. BV of test Protein =[ I- (F-Fo)-(U-Uo) / I-( F-Fo) ]x 100 = Nitrogen retained/nitrogen absorbed
a. I, intake of nitrogen
b. F, fecal nitrogen
c. Fo, fecal nitrogen on nitrogen free diet
d. U, urinary nitrogen
e. Uo, urinary nitrogen on nitrogen free diet
The nitrogen lost in urine measures the nitrogen that has been absorbed and used by the body
while the nitrogen lost in the faeces measures the nitrogen that has not been absorbed．
2. BV is a measure of nitrogen retained for growth or maintenance and expressed as a percentage
of N absorbed.
3. like a balance study, needs fecal and urinary collections.
4. includes an evaluation of digestibility as well as content of indispensable amino acids.
5. proteins exhibit a higher BV when fed at levels below the amount necessary for nitrogen
equilibrium. As intake of protein approaches or exceeds adequacy, retention decreases.
④ Net Protein Use (NPU)
The product (乘积) of the coefficient of digestibility and of the biological value is called the net
protein utilization (NPU) or the percentage of dietary nitrogen (or protein) retained. For “true”
values, the endogenous fecal and urinary losses of nitrogen (measured on a protein-free diet)
should be taken into account as follows.
Where i is the ingested, f is the fecal, and u is the urinary nitrogen, and e stands for
endogenous. This method is easily applicable to nongrowing humans.
For small growing animals, the nitrogen retained can be determined directly by total
carcass analysis:
Protein quality and amino acid availability also can be determined in humans or animals by a
number of other methods:
by repletion tests (regeneration of plasma proteins, or of body weight);
by measuring changes in enzyme activity levels;
by monitoring changes in the plasma level of free essential amino acids after ingestion of the
test protein under standard conditions;
and by measuring levels of urea in the plasma and the urine.
The various bioassays tend to provide essentially the same ranking with respect to the nutritive
value of different proteins. Most of these assays can also detect deterioration of protein quality
during processing, provide the process affects the limiting amino acid. All bioassays with the
exception of the one that involves measurement of plasma amino acids, give a result based on a
limiting amino acid and do not provide information on the balance of other amino acids.
Furthermore , none of the bioassays can be used to predict the complementary value of
proteins in mixed diets.
Also, bioassays do not identify the limiting amino acid of the test protein or diet, unless
several additional experiments are carried out in the presence of added free amino acids.
Finally, bioassays are expensive and time consuming, and extrapolating (外推) animal results
to humans involves considerable uncertainty.
Limiting Amino Acid
•
•
An inspection of animal protein shows that eggs，milk and beef are high－quality proteins
because they contain all the essential amino acids and in sufficient amounts to meet the
needs of an adult．
However，in other protein foods one or more amino acids may be present in amounts that
are below human requirements．The amino acid which is furthest below the human
requirement is known as the limiting amino acid．The limiting amino acid in a variety of
foods is shown in Table
Essential amino acid content of high quality animal proteins (mg/g protein)
Limiting amino acids in animal and plant foods
(2) Chemical Methods
• In most chemical methods, a proteins nutritional value is assessed on the basis of essential
amino acids as compared with the human requirements for these amino acids.
• The protein quality of a food can be evaluated in chemical terms by measuring its amino
acid content and comparing it with that of a reference protein．Whole egg protein is
usually taken as the reference protein and given a score of 100．Chemical score values are
found to match up fairly well with biological values .
Protein quality of some foods comparing BV, NPU and chemical values
What is “chemical score” of protein?
A protein “chemical score” is defined as:
Chemical scores based on lysine, sulfur amino acids, tryptophan, or threonine are probably the
only ones of practical importance since these amino acids appear to be the only limitation ones in
most human diets.
The chemical score allows one to calculate the requirement of a single food protein or of a
protein mix. For example, the requirement of a given protein mix would be calculated as:
•
Knowledge of the chemical scores (for all essential amino acids) of various protein
permits calculation of the complementary value of different protein in a mixture.
• Widely and successfully used in animal feeding,
• the chemical score also has been used to develop protein-rich food mixes for developing
countries.
• However this approach may underestimate the quality of a protein for adults, since it is
based on the amino acid requirements of the young child.
• Another drawback of the chemical score method lies in the fact that accurate analyses of
tryptophan and sulfur amino acids require special techniques.
• It also does not account for the negative effects of excess amino acids or of antinutritional
factors present in the protein food.
• Furthermore, it does not compensate for differences in the digestibility of proteins or in
the biological availability of specific amino acids.
The correlation between the results of bioassays and the results of chemical scores is improved
when the chemical scores are corrected based on overall protein digestibility. The later can be
determined by rapid in vitro enzymic tests. Such corrected amino acid scores can be correlated
with PER values to give a computed PER (C-PER). Data on available lysine obtained from the
chemical method of Carpenter, or from dye-bonding methods, also can be used to correct chemical
scores.
(3) Enzymic and Microbial Methods.
• Enzymic methods for evaluating protein quality are based on the measurement of free
essential amino acids released after the test protein has been exposed to the action of one
or more proteases under standard conditions.
• Such methods can provide estimates of protein digestibility, protein value, and/or
bioavailability of specific amino acids.
• Their use is of great interest for rapidly evaluating the damage incurred by protein foods
or feeds during industrial processing and storage.
Some microorganisms, especially the protozoan (原生动物) Tetrahymena 四膜虫 pyriformis,
possess essential amino acid requirements similar to those of humans and the rat.
These microorganisms also possess their own proteolytic enzymes. Their growth on test
proteins can therefore be used as an index of protein quality or amino acid availability.
4. Recommendation
Histidine :8-10 mg/kg/day - Adults, 18yrs and older
Food Sources：Pork, poultry, rice, wheat, cheese
Isoleucine :31 mg/kg/day - Preschool, 2-5 yrs
28 mg/kg/day - Schoolchildren, 10-12 yrs
10 mg/kg/day - Adults, 18yrs and older
Food Sources：Eggs, fish, lentils, poultry, beef, seeds, soy, wheat, almonds, dairy
Leucine: 73 mg/kg/day - Preschool, 2-5 yrs
44 mg/kg/day - Schoolchildren, 10-12 yrs
14 mg/kg/day - Adults, 18yrs and older
Food Sources：Eggs, fish, lentils, poultry, beef, seeds, soy, wheat, almonds, dairy, beans,
brown rice
Lysine : 64 mg/kg/day - Preschool, 2-5 yrs
44 mg/kg/day - Schoolchildren, 10-12 yrs
12 mg/kg/day - Adults, 18yrs and older
Food Sources：Fish, eggs, dairy, lima beans, beef, soy, yeast, potatoes
Methionine: 27 mg/kg/day - Preschool, 2-5 yrs
22 mg/kg/day - Schoolchildren, 10-12 yrs
13 mg/kg/day - Adults, 18yrs and older
Food Sources：Fish, eggs, dairy, beans, beef, garlic, onion, lentils, soybeans
Phenylalanine : 69 mg/kg/day - Preschool, 2-5 yrs
22 mg/kg/day - Schoolchildren, 10-12 yrs
14 mg/kg/day - Adults, 18yrs and older
Food Sources: Dairy, almonds, avocados, lima beans, peanuts, seeds
Threonine: 37 mg/kg/day - Preschool, 2-5 yrs
28 mg/kg/day - Schoolchildren, 10-12 yrs
7 mg/kg/day - Adults, 18yrs and older
Food Sources: Dairy, beef, poultry, eggs, beans, nuts, seeds
Tryptophan: 12.5 mg/kg/day - Preschool, 2-5 yrs
3.3 mg/kg/day - Schoolchildren, 10-12 yrs
3.5 mg/kg/day - Adults, 18yrs and older
Food Sources: Dairy, beef, poultry, barley, brown rice, fish, soybeans, peanuts
Valine: 38 mg/kg/day - Preschool, 2-5 yrs
25 mg/kg/day - Schoolchildren, 10-12 yrs
10 mg/kg/day - Adults, 18yrs and older
Food Sources: Eggs, mushrooms, nuts, poultry, beef, soy, grain, dairy
Recommended intakes of Protein
RDA's for healthy adults = 0.8 grams per kilogram of body weight - or about 15% of total
calories Protein needs are higher for children, infants, and many athletes.
Protein content of a selected number of foods (g/100g food)
Food
White rice, cooked
Pasta, cooked
White bread
Semi-skimmed milk
Cheddar cheese
Poached egg
Rump steak, grilled
Peanuts
Recommendation
Amount of protein
(g per 100g of food)
2.6
7.7
7.9
3.4
25.4
12.5
31
25.6
Preschool,
2-5 yrs
Schoolchildren,
10-12 yrs
Histidine
Isoleucine
31 mg/kg/day
28 mg/kg/day
Adults,
18yrs and older
Food Sources
8-10 mg/kg/day
Pork, poultry, rice, wheat, cheese
10 mg/kg/day
Eggs, fish, lentils, poultry, beef,
seeds, soy, wheat, almonds, dairy
Leucine
73 mg/kg/day
44 mg/kg/day
14 mg/kg/day
Eggs, fish, lentils, poultry, beef,
seeds, soy, wheat, almonds, dairy,
beans, brown rice
Lysine
64 mg/kg/day
44 mg/kg/day
12 mg/kg/day
Fish, eggs, dairy, lima beans,
beef, soy, yeast, potatoes
Methionine
27 mg/kg/day
22 mg/kg/day
13 mg/kg/day
Fish, eggs, dairy, beans, beef,
garlic, onion, lentils, soybeans
Phenylalanine
69 mg/kg/day
22 mg/kg/day
14 mg/kg/day
Dairy, almonds, avocados, lima
beans, peanuts, seeds
Threonine
37 mg/kg/day
28 mg/kg/day
7 mg/kg/day
Dairy, beef, poultry, eggs, beans,
nuts, seeds
Tryptophan
12.5 mg/kg/day
3.3 mg/kg/day
3.5 mg/kg/day
Dairy, beef,
brown rice,
peanuts
poultry, barley,
fish, soybeans,
Valine
38 mg/kg/day
25 mg/kg/day
10 mg/kg/day
Eggs, mushrooms, nuts, poultry,
beef, soy, grain, dairy
Part 4. Lipids and colloids
1.What is a Fat?§A fat, or Lipid - is made
up of a molecule of glycerol in which one or more
of its three original hydroxyl groups have been
replaced by fatty acid chains.
§Approximately 95% of food lipids fall into a
group called triglycerides (all three glycerol -OH
groups are replaced). Other important lipids are phospholipids (e.g. emulsifying agents such as
lecithin) and sterols (e.g cholesterol).
§Lipids can be liquid at room temperature, as in canola
oil, or solid, as in margarine.
1) Triglycerides§The nature and properties of lipids are
related to the type of fatty acids present.
§Fatty acids from plants and animals are different affecting both their physical and chemical properties:
The three hydroxyl groups of the glycerol molecule can each combine with a laity acid molecule
and the resulting ester is called a triglyceride.
2) Phospholipids§Phospholipids are a
combination of fats plus phosphate,
some forms also contain nitrogen.
§Phospholipids are similar to fats in
that they have a structure based on
glycerol but instead of the three
hydroxyl groups being combined with a
fatty acid（see below）only two are so
combined，the third being combined with phosphate linked to choline．
§Lecithin(卵磷脂) is the best known example of a phospholipid. It is synthesized by both plants
and animals, and is found in foods such as egg yolk and soybeans.
§Sphingolipids (神经)鞘脂类,
Function of phopholipids§1) Lecithin is a source of choline, a compound required for fat
transport and sometimes listed as one of B-complex vitamins.
§2) Affect the synthesis of neurotransmitters (such as serotonin (复合胺), acetylcholine,
dopamine(多巴胺) and norepinephrine 去甲肾上腺素) in brain。
§3) Are important components of membrane structure.
3) Sterols
§ Sterols
can
be
plants and animals, are
phyto-sterols (ergosterol
HO
sitosterol 谷 固 醇 ) and
individually.
§Cholesterol is an essential constituent of the cell membrane of every
synthesized
by
called
as
麦 角 固 醇 and
cholesterol
cell. About 80% is
produced in the body by the liver. 20% is influenced by diet through excess calories, fat and
dietary cholesterol. It is needed for the formation of vitamin D, Steroid hormones, and bile acids
needed for the digestion of fats. (function)
§But if it is excessive, it will cause vascular diseases.
§Phyto-sterols are thought to decrease the absorption of cholesterol.
2. The type
of Fatty Acids
§According as there is or not double bonds
§1. Saturated - no double bonds, e.g. acetic acid CH3COOH, (vinegar), lard.
§2. Unsaturated -§Monounsaturated - one double bond, e.g. Oleic acid (油酸 ) (Olive oil)
CH3(CH2)7CH=CH(CH2)7COOH
§ Polyunsaturated - two or more double bonds, e.g. Linolenic acid (Linseed oil)
C17H29COOH has three double bonds.
§oleic acid CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH
棕榈油 16:0
Palm Oil 油酸 18:1 n-9
Oleic acid
亚油酸 18:2 n-6 亚麻酸 18:3 n-3§According to length of carbon chain - acetic acid has a
one carbon chain, oleic acid has a 17 carbon chain.
§Short chain fatty acids: less than 6 carbon chain.
§Medium chain fatty acids: 8-12 carbon chain.
§Long chain fatty acids: more than 14 carbon chain.
Cis and trans fatty acids
§When two carbon atoms are joined by a double bond there is
not freedom of rotation about the axis of the double bond．
Consider oleic acid．In one form the two
parts of hydrocarbon chain are on the same side of the double bond（cis form）while in the other
they
are
on
opposite
sides
of
the
double
bond
（
trans
form）
．
CH3(CH2)7CH=CH(CH2)7COOH
§ Naturally occurring unsaturated fatty
acids have cis forms while the corresponding trans forms lack. Essential fatty acid (EFA) activity
enzymes can recognize the difference between cis and trans forms，acting on the former but not
the latter．§ The distinction that is drawn between cis and trans fatty acids may seem like an
unnecessary complication but it has some relevance when considering the relationship between the
types of fat we eat and our health.
Cis
form (oleic acid)
Trans form (elaidic acid)
Figure 4.1 Cis and trans forms of a fatty acid 3.
Physical Properties
of fatsSaturated fats
§Have high proportion of saturated fatty acids such as myristic and palmistic.
§Usually are solid at room temperature.
§Usually are found in animal foods-beef, pork, lamb, milk, cheese; exceptions are coconut and
palm oil.
§Are thought to increase the level of cholesterol in blood.
3. Properties of Fat§Polyunsaturated fats
§Have high proportion of polyunsaturated fatty acids such as linoleic, linolenic acid (from
plants)and arachidonic acids (from animals)
§Usually are liquid at room temperature.
§Usually come from plants- soy, corn, safflower, exception are fish
§Are thought to decrease the cholerterol level in blood.
§Monounsaturated fats
§Are found in olive oil and peanut oil (oleic is the most common MUFA)
§Are thought to have a neutral effect on blood cholesterol
4. Describing Fatty Acids§Fatty acids are described by the ratio of
the number of carbon atoms in the chain to the number of double bonds and the position of the
double bond is thought to have significance in health issues.
§Linoleic acid （亚油酸）is 18:2 omega-6 fatty acid i.e it has an 18 carbon chain, two double
bonds and the double bond lies between the sixth and seventh carbon atoms. Linolenic acid（亚麻
酸） is 18:3 omega - 3 fatty acid.
Omega 3
CH3-CH2-CH=CH-CH2-CH=CH-CH2-CH=CH-(CH2)7-COOH
α- Linolenic Acid (18:3 ω 3)
18 Carbons long
3
Carbon-carbon
double bonds
Omega
6
CH3-CH2-CH2-CH2-CH2-CH=CH-CH2-CH=CH-(CH2)7-COOH
Linoleic Acid (18:3 ω 6)
18 Carbons long
First double bond 3 carbons from
methyl end
3\
Examples
Carbon-carbon
of ω-3 and ω- 6 polyunsaturated
double bonds
fatty acids
TableFirst
1. Common
PUFAbond
double
Trivial Name
6 carbons
from
Abbreviation
Omega system
methyl end
α-Linolenic
Eicosapentaenoic
Docosapentaenoic
Docosahexaenoic
Linoleic
γ -linolenic
Dihomo-γ-linolenic
Arachidonic
Docosatetraenoic
docosapentaenoic
18:3ω3
20:5ω3
22:5ω3
22:6ω3
18:2ω6
18:3ω6
20:3ω6
20:4ω6
22:4ω6
22:5ω6
LNA
EPA
DPA(ω3)
DHA
LA
GLA
DGLA
AA
DTA
DPA
Tab.2 The commen fatty acids
Name
describing
Elaidic acid
C18:1,n-9 trans (反油酸)
Butyric acid
C4:0（丁酸）
Linoleic acid
C18:2,n-6, all cis
Caproic acid
C6:0 已酸
Linolenic acid
C18:3,n-3,6,9all cis
Caprylic acid
C8:0 辛酸
γ-Linolenic acid
C18:3,n-6,9,12all cis
Capric acid
C10:0 癸酸
Arachidic acid
C20:0 花生酸
Lauric acid
C12:0 月桂酸
Arachidonic acid
C20:4,n-6,9,12,15all cis
Myristic acid
C14:0 肉豆蔻酸
Eicosapentaenoic
acid
C20;5,n-3,6,9,12,15
(EPA)
cis
all
Palmitic acid
C16:0 棕榈酸
Erucic acid
C22:1,n-9 cis 芥子酸
Palmitoleic acid
C16:1,n-7 cis 棕榈油酸
Clupanodonic acid（DPA)
C22:5 ,n-3,6,9,12,15 all
cis
Stearic acid
Oleic acid 油酸
C18:0 硬脂酸
C18:1,n-9 cis
Docosahexenenoic
Acid
C22:6
,n-3,6,9,12,15,18
(DHT)
all cis
Nervonic Acid
C24:1, n-9 cis 神经酸
5. Fats function in the Body§In our body, lipids or fats (fatty
acids) have several essential and important functions.
Fats
•store food energy - when metabolized fats release more energy than any other food constituent.
i.e. 2.25x more than protein.
•insulate the body and protect body and organs such as kidneys from damage.
•are essential parts of cell walls and and membrane of cell and organs.
•are necessary for the production of various hormones and vitamin D.
•are important for the production of sterols which are found in all animals and plants. However,
only cholesterol is found in animals.
•are essential transport agents for fat soluble vitamins around the body tissues.
Function
§1). Structural element in membranes
Lipoid can be found in many tissues and cells, for example: Membrane is a kind of lipoid
layer which consists of Phospholipids, Glycosphingolipids and Cholesterol. And sterols is
indispensable in the sterols hormone’s product in human body.
§2). Storage forms of metabolic fuel
Lipids are one of the three main classes of food,
along with carbohydrates and proteins. They are responsible for storing energy that animals do not
immediately need. If needed, they can produce energyby metabolism at any time.
§3). Assist in absorption of lipid-soluble vitamins
Some lipid-soluble vitamins, such as vitamin A, vitamin D, vitamin E and vitamin K are
also belong to lipids. The food fat can help the body to absorb them.
Structure and Functions §4). Immune recognition
In addition, lipids can not only insulate heat but also support and protect the viscera
inside the body, keep them away from damage.
§5). Food sense intensifier
Lipids stay long in the stomach as compared with glucide
and the protein. It takes 4 to 6 hours to digest some food which contain 50 g fat. So, people
always feel full. Besides, lipids can ameliorate the sense and the capability of food. For example,
deepfried food has a special scent.
6. Essential fatty acids§Small amounts of fat are essential for human nutrition. One essential fatty
acid, linoleic acid, must be supplied in the diet, since the body cannot produce enough.
§Linolenic acid and arachidonic acid were once considered essential. However, we now know
that the body can convert linoleic acid to arachidonic acid and linolenic acid can only partially
replace linoleic acid.Figure 2. ω-3 and ω- 6 polyunsaturated fatty acids metabolism
△6Desaturase
18:2ω6
elongase △5Desaturase
elongase △4Desaturase
18:3ω6
20:3ω6
20:4ω6
22:4ω6
22:5ω6
20:2ω6
22:2ω6
△6Desaturase
elongase △5Desaturase
elongase △4Desaturase
18:3ω3
18:4ω3
20:4ω3
20:5ω3
22:5ω3
22:6ω3
elong
beta-ox
24:5ω3
24:6ω3
7. Function of Essential fatty acids
§1) These fatty acids are necessary for the
production of prostaglandins(前列腺素), thromboxanes（凝血素） and several other compounds.
Prostaglandins and thromboxanes affect nearly every physiological system in the body.
§ 2) Important composition of phospholipids, which are part of the structure of all cell
membranes． .
§ 3) Affect the metabolism of cholesterol. LDL-Ch, HDL-Ch are carrier of
Cholesterol.Deficiency symptoms of essential fatty acids § Deficiency symptoms of
essential fatty acids include decreased growth, dermatitis, fatty liver, impaired reproduction and
impaired water balance.
§There is evidence omega-3 fatty acids (found in fish) are important in prevention of heart
disease.
8. Digestion of fats1)In the mouth: sublingual salivary glands (舌下腺) secrete lingual
lipase
Chewing disperses fats into smaller particles, and the solid fats are warmed by the body
and become liquid
2)In the stomach: (fat floats above other food components)
•Lingual lipase may continue to hydrolyze one bond from triglycerides to form diglycerides and
free fatty acids
•Stomach churns and mixes fat with water and acid
•Gastric lipase hydrolyzes some fat in the emulsified (not much) 。
•An emulsified fat is dispersed in tiny particles having a large amount of surface area that can be
acted upon.
3) In the small intestine:§CCK (cholecystokinin 肠促胰酶肽) signals gallbladder (胆囊)
to release bile for emulsification of fat.
§Pancreatic lipase enters from pancreas through the pancreatic duct - breaks down triglycerides
to a monoglyceride or occasionally to a glycerol and free fatty acids.
§Intestinal lipase also acts on triglycerides with pancreatic lipase .
§Bile is either reabsorbed and recycled or trapped by dietary fiber and excreted: if excreted, the
liver must make more bile from cholesterol (effectively lowering blood cholesterol).
§Bile acids are derivatives of cholesterol synthesized in the hepatocyte.
§Bile acids are amphipathic(两性分子的)
§Two important functions of bile acids :
•Emulsification of lipid aggregates: Bile acids have detergent action on particles of dietary fat
which causes fat globules to break down or be emulsified into minute, microscopic droplets.
Emulsification is not digestion per se, but is of importance because it greatly increases the surface
area of fat, making it available for digestion by lipases, which cannot access the inside of lipid
droplets.
• Solubilization
and transport of lipids in an
environment: Bile acids are
aqueous
lipid carriers and
are able to solubilize many
lipids
by
forming micelles (胶束,胶态
aggregates of lipids such as
离
子
)fatty
acids,
cholesterol
and
monoglycerides
- that remain suspended in
water. Bile acids are also critical for transport and absorption of the fat-soluble vitamins.
9. Lipid Absorption 1)Some glycerol, short-chain fatty acids, and
medium-chain fatty acids (≦12 carbons) can be absorbed into the blood stream (the portal
vein) by diffusing the intestinal cells. They are attached to albumin to the liver. (1/3 fats)
2)Monoglycerides and long-chain fatty acids(≧14 carbons) merge into micelles (spherical
shaped complexes 微团) for transport through the microvilli(微绒毛) of intestinal cells. (2/3
of fats)
3)When micelles diffuse into intestinal cells - the monoglycerides and long-chain fatty acids
are reassembled into triglycerides and carried away by joined to proteins and phospholipids
into complex substances called chylomicrons (CM) and very low-density lipoprotein
(VLDL) . These are released in the lymph system and transported to the vein, where they go
to the liver.
4)During digestion, the fats are attached to bile salt, which makes them water soluble. As
they are absorbed, the bile salts split off.
10. Lipid Transport
§Fat are insoluble in water. This characteristic is
important because it means that they must be combined with a water-soluble substance, usually
protein (as lipoproteins), to be transported in the blood and lymph systems.
§1). Chylomicrons
§largest and least dense lipoprotein
§transports diet-derived lipids (primarily triglycerides) from the intestine to the cells of the body.
2). VLDL (Very Low Density Lipoproteins)§made by the liver to transport
liver-synthesized lipids (primarily triglycerides) to the cells of the body
§as it loses triglycerides, they collect cholesterol from other lipoproteins and become LDL
3). LDL (Low Density Lipoproteins)§composed mostly of cholesterol
§carries and deposits cholesterol to tissue cells: muscle, fat stores, mammary glands, heart, etc...
§the liver can control the amount of LDL in circulation
§(LDL is excessive, it implicates to increase danger of heart disease.)
4). HDL (High Density Lipoproteins)
§Smallest lipoprotein, is the
most protein-dense lipoprotein
§carries cholesterol and phospohlipids from the cells back to the liver for recycling or disposal.
§(High HDL can decrease the danger of heart disease.)
5). Factors that improve LDL:HDL ratios: (1) weight control
(2) monosaturated or polyunsaturated fatty acids in place of saturated fat
(3) soluble fiber
(4) antioxidants
(5) moderate alcohol consumption
(6) physical activity
6) Plasma Lipoprotein (血浆脂蛋白)§Plasma Lipoprotein
：Lipids in Plasma,
called lipoprotein 。
§Lipids：500mg%lTG：100mg%lPhospholipids (PL)：200mg%；Lecithin (卵磷脂) 70%，神
经鞘磷脂 20%，Cephalin (脑磷脂)10%
l Ch And CE：200mg%；Ch:55mg%,CE:145%mg%
lFFA ： 55mg%
Lipoprotein
Classes 、 Composition and Structure of Plasma
§Classes：
lelectrophoresis (电泳法)：CM、β、 pro-β、α
lultracentrifugation (超离心法)：CM ( chylomicron )、VLDL (very low density lipoprotein)、LDL、
HDL
CM
¦Â
Ç°¦Â
¦Á
+
£+
£-
Ѫ½¬
Ö¬
µ°°×ÇíÖ¬
ÌÇÄý½ºµçÓ¾
§Composition：TG，Ch, CE，PL， apolipoprotein,apo（载脂蛋白）
血
CM
VLDL
0.950
蛋
LDL
1.006 1.019
IDL
CM
VLDL
d=80-500nm
Pr=0.5-2%
TG=80-95%
PL=5-7%
C=1-4%
apoA
apoB48
apoC
—ultracentrifugation
HDL
1.063
1.125
1.210
HDL2
白的
HDL3
LDL
分类
HDL
d=25-80
d=20-25
d=7.5-10
Pr=5-10%
Pr=20-25%
TG=10%
PL=20%
C=45-50%
apoB100
apoE
Pr=50%
TG=5%
PL=25%
C=20%
TG=50-70%
PL=15%
C=15%
apoB100
apoC
apoE
浆脂
apoAⅠ
apoAⅡ
apoC
apoE
apoD
Structure of Lipoprotein
apoprotein
C
PL
TG
apoproteinB100
CE
11. Sources of Fatty Acids in Food
§Good food sources
of linoleic acid and somewhat lesser amount of linolenic acid, include seed oils from corn, cotton,
soybean (50% linoleic acid) and peanuts (20-30% linoleic acid) as well as chicken fat.
§most other animal fats are low in this essential fatty acid.
§ Linseed (亚麻子) oil is an excellent source of linolenic acid.
Source
High Fat Foods
Oils, salad, cooking
Butter and Margarine
Mayonnaise
Fat
100%
Conte
80%
nt 80%
Walnuts
64%
Chocolate
53%
Pork sausage (cooked)
45%
(unsweetened
Cheese
Olives
)
30%
16-20%
Cakes, Cookies
10-25%
Ice Cream
10-16%
Meats
4-15%
Part 5
The Energy and Nutrition
What is energy?Energy is the power used to do work or to produce heat or light. Energy cannot
be created or destroyed but it can be changed from one form to another. For example, when a piece
of coal burns, the energy locked up in the chemicals in the coal is converted to heat and light.Where
does energy come from?Energy comes from the sun and is called solar energy. Living plants
are able to convert solar energy to chemical energy by a process called photosynthesis.
This chemical energy is used to make other substances such as protein, carbohydrate
and fat, all of which provide energy.
Plants extract energy from light with 35% efficiency.
Animals cannot use solar energy directly but can use the chemical energy contained in
plants or other animals. They can oxidize carbohydrate, protein, fat (and alcohol) to
produce energy, carbon dioxide and water.
Animals extract energy from food with 25-30% efficiency.The importance of energyAll
living organisms require a source of energy
Some of the energy released is used to maintain metabolic process in the cells
Some of the energy is converted into heat to maintain body temperature
Some of the energy is converted into mechanical energy which is used for physical
activity
Units of energyEnergy can be measured in either joules or calories.
• A joule (J) can be defined as the energy used when 1 kilogram (kg) is moved 1 meter (m) by the
force of 1 Newton (N).
• A calorie (cal) can be defined as the energy needed to raise the temperature of 1 gram of water
from 14.5 to 15.5ºC.The unit of energy are the joule, kilojoule(KJ)
megajoule(MJ), kilocalorie(Kcal), megacalorie
1kcal=4.18kJ
1MJ=1000KJ= 1000000J
Energy value of nutrientsThe three groups of nutrients which provide the body with
energy are carbohydrates,fats and proteins
1g of carbohydrates provides 17KJ (4kcal)
1g of fat provides 38KJ (9kcal)
1g of protein provide 17kj (4kal)
Alcohol make a significant contribution to the energy value
1g of alcohol provide 29KJ (7kcal)Energy value of foods
Food
KJ per 100g
Kcal per 100g
Butter
3041
740
Cheese
1682
406
Sugar
1660
349
White
flour
1493
Beef
1168
282
Eggs
612
147
Potatoes
372
87
Bananas
337
79
356
Milk
272
65
Beer
105
25
Use of energy by the bodyBasic metabolism
Physical activity
Metabolic response to food
1. Energy Expenditure A. 24 hour EE = REE + TEF +TEE + FT (?) EE, Energy
Expenditure REE, Resting Energy Expenditure TEF, Thermic Effect of Food TEE,
Thermic Effect of Exercise FT, Facultative ( 特 许 的 )Thermogenesis ( 生 热 作 用 )1).
Basal Metabolism The minimum amount of energy needed to maintain life.
a. rested quietly for 30 mins
b. postabsorptive for at least 12 hours
c. thermally neutral environment
e. no exercise for 24 hour prior
Basic metabolismEnergy is needed to …
Keep the heart beating
Keep the lungs functioning
Maintain body temperature
For the numerous chemical reactions taking place in body cells
The rate at which energy is used up in maintaining basal metabolism is called
Basal metabolic rate (BMR)
BMR can be measured by
determining the amount of heat given out by the body
1.Enclosing the person in an insulated chamber and measuring heat output
2.For the person to breathe into specially designed apparatus which monitors either
oxygen uptake or carbon dioxide output
Factors affect the BMR of an
individualBody size
BMR of an average 70kg man is 293KJ per hour
BMR of an average 55kg woman is 251KJ per hour
Activity of the thyroid gland
Thermogenic( 生 热 ) effect of foodPercent BMR
Species
% BMR
Elephant
2.7
Horse
1.8
Pig
1.0
Man
19.6
Sheep
1.7
Monkey
8.8
Dog
2.9
Rat
2.1
Mouse
1.7
Utilized
By
Brain
2). Resting Energy Expenditure (REE) - a. Any measurement that is not
BMR
b. 60-70% of total daily energy expenditure
c. thyroid function, nutrition state, exercise, and sympathetic nervous (交感神经) system
can affect RMR
d. decrease in RMR with age appears to be due to loss in lean body mass
e. in women, a decrease in RMR is seen after menopause(更年期)(Curvilinear)3).
Thermic Effect of Food (TEF).a. the energy cost associated with digestion,
absorption, transport, and storage of nutrients. b. accounts for ~ 10% of daily energy
expenditure c. cost of storing fat is 3% of the available energy from fat d. cost of
storing glucose as glycogen is 7% of available energy from glucose
e. cost of storing glucose as lipid is 26% of available energy from glucose
f. cost of storing protein is 24% of available energy from protein
g. measurement of TEF varies considerably
4). Thermic Effect of Exercisea. The energy cost of physical activity above
basal levels
b. 15-30% of daily energy expenditure
c. two components: 1) during exercise; 2) after exercise
d. highly variable -- intensity 强度+ duration
e. difficult to estimate spontaneous activity [自发性活动]
5). Facultative
Thermogenesisa. 10% of
daily energy expenditureb. a
catch-all for energy expenditure
not accounted for by RMR, TEF,
and
TEE
2.
Measuring
Energy Expenditure 1)
Direct Calorimetry
(Direct) A simplified
version of human calorimeter used to measure direct body heat
lose, energy expenditurea.
specially design chamber that measures body
heat
b. very impractical, but very accurate 2).
Indirect Calorimetry (Oxygen
Consumption) a. closed circuit: The subject rebreathes only the gas within the
spirometer. Measurement of oxygen consumed from a know amount. b. open circuit: the
subject breathes through a two-way valve in which room air is inspired from one side and
expired air passes through the opposite side. A sample of the air is collected an analyzed.
Gas laws must be applied to the equation for determining oxygen consumption and
carbon dioxide production c. takes advantage of the fact that energy metabolism
ultimately depends on oxygen utilization (VO2) and carbon dioxide production (VCO2) d.
one liter of oxygen is approximately equal to 5 kcal (assuming a mixed diet).
3). Doubly Labeled Water a. subject drinks a known amount of water
labeled with the stable isotopes deuterium (2H) and oxygen 18 (18O). b. collect urine
and blood samples for 1-3 weeks.
4). Respiratory Quotient (RQ) (1) the ratio of CO2 to O2
consumed (RQ) (2) Gives an indication of the type of food stuff being
consumed (RQ Equivalents)
a. the RQ for carbohydrate is 1.0
b. the RQ for fat is 0.71
3. Estimation of Energy Allowances in Populations 1). Adults
(1). World Health Organization (WHO) REE values are multiplied by activity factor a.
WHO recommendation are based on empirical (完全根据经验的) derived equations
b. activity factors are multiplies of REE and rely on a system that divides activity into
different classification: very light, light, moderate, heavy (Exercise Chart).
Physical activityIn addition to basal
metabolism, energy is used by the body for
muscular activity.
The energy requirements for various
activities have been determined by
measuring oxygen uptake during different
activities
Energy consumption of various activities
Activity
KJ per minute
Kcal per minute
Sitting
6
1.4
Standing
7
1.7
Walking
14-21
3.3-5.0
Running
25-65
6.0-15.6
Swimming
20-50
4.8-12.0
Football
20-35
4.8-8.4
Agricultural work
15-30
3.6-7.2
Coalmining
30-40
7.2-9.6
Walking up and downstairs
38
9
Estimated Calorie expenditures of various Activities
Activity
Cals/min
Baseball
3.4-4.0
Class work
1.0-2.0
Cycling (14 kph)
7.0
Dancing (fast)
4.0-7.0
Driving Car
2.0
Driving Motorcycle
2.8-3.5
Eating
2.0-3.0
Football
8.9-12.0
Golf
5.0
Hockey
12.0-15.0
Jogging
10-15
Running (slow-fast)
10-14.5
Skiing (fast)
15.0-19.0
The body
is unable to
Watching TV
1.5-1.6
completely
convert chemical energy from food into mechanical energy ,the efficiency of conversion is
only 15—20 %.
Heat
Sleeping
Body temperature
1.0-1.2
(2). Agea.
young
adults (19-24) are more active than older age
groups and thus will have REE multiples that
are greater.
b. assumption made that younger adults have
more lean body mass than older adults: the
estimate for REE is higher
c. assumption made that older adults (51+) are less active and therefore the REE
multiples are lower than younger age groups (3).
Gender a. men have
proportionately greater muscle mass than do women: REE per unit of total body weight
differs by approximately 10% between the genders.
b. occupational activity requirements now are similar (4).
Pregnancy a. gross
energy cost for a full term 3.3 kg baby and 12.5 kg weight gain by the mother is
estimated at 80,000 kcal.
b. the increase in the energy allowance during pregnancy is distributed over the
trimesters: 1st, +0; 2nd, +300; 3rd, +300 (5).
Lactation a. requirement for lactation
is proportional to the quantify of milk produced
b. energy content of human milk is about 70 kcal/100 ml
c. efficiency of production is about 80%; thus energy cost is 85 kcals/100 ml
d. Average milk secretion is 750 ml/day
e. thus, upper boundary of the requirement would be ~ 640 kcals extra per day.
2). Infants, Children, and Adolescents (1). the energy requirement is estimated
from intake associated with normal growth a. current requirement is 108 and 98 kcal/kg
for 0-6 months and 6-12, respectively
b. studies using double labeled water suggest a requirement that is 15% lower
c. normal growth usually means the large gain in weight (without obesity) per kcal
eaten (link to growth curves)
d. is bigger better? (2). the energy requirements for children (1-10 years) and
adolescents (11-14) reflect: a. growth rates
b. high levels of activity
c. differences in sexual maturity
Age and sex
BMR varies from person to person both within a population group and between
different groups.
Infants and young children have a proportionately high BMR for their size due to
their rapid growth and development.
Men usually have a higher BMR than women since they tend to have more
muscle.
Older adults usually have a lower BMR than the young since the amount of
muscle tends to decrease with age.
The BMR accounts on average for about three quarters of an individual's energy
needs.4.Energy requirementsRecommended daily energy intake divide men
into three occupation categories:
1.sedentary—office and shop worker, most professional people
2.Moderately active—people engaged in light industry, postmen, bus conductors,
most farm workers
3.Very active—coalminers, steelworkers, army recruits, some farm workers
Recommended daily amount of food energy
occupational category
KJ
kcal
Men,
sedentary
10500
2510
18-34 years
moderately active
12000
2900
Women ,
18-54 years
Age
14000
9000
10500
EAR - MJ/day (kcal/day)
Boys
Girls
4-6 months
2.39 (690)
2.69 (645)
7-9 months
3.44 (825)
3.20 (765)
10-12 months
3.85 (920)
3.61 (865)
1-3 years
5.15 (1230)
4.86 (1165)
4-6 years
7.16 (1715)
6.46 (1545)
7-10 years
8.24 (1970)
7.28 (1740)
11-14 years
9.27 (2220)
7.72 (1845)
15-18 years
11.5 (2755)
8.83 (2110)
0-3 months
5.
very active
most occupations
very active
2.28 (545)
2.16 (515)
3350
2150
2500
Estimated Average
Requirements for
energy (children and
adolescents aged 0-18
years).
ObesityIf energy
input is equal to energy output, body-weight remains constant
If energy input is greater than output, the excess food is converted into fat
and obesity results
Energy Balance = Energy Input - Energy Output
Obesity can cause…Not beautiful
It reduces life expectancy and is related to coronary heart disease and various other
conditions including high blood pressure and varicose veins
It also increase the chances of developing diabetes in middle life Factors of
obesityHeredity
Reduced physical activity
Eating habits
Psychological factors
Endocrine factors
TreatmentDiet
Activity
Diet:The nutrients that provide us with calories for energy include carbohydrates, fat and
protein.
The composition of a high energy diet should be over 60% carbohydrates, less than
25% fat and 15% protein.
It is not advisable to cut down on protein
It is sensible to restrict fat intake by cutting down on the intake of fried food, butter,
cream, fatty meat, etc.
Carbohydrate intake should be reduced but by restricting sugar rather than starch
Alcoholic drinks in excess can lead to obesity and it is sensible to restrict drinking to lose
weight Food Intake factors Hunger: physiological drive for food
Appetite: a response to sight, smell, or taste of food that prompts or delays eating
Satiation: full feeling of satisfaction as a result of stretching receptors in the stomach
Satiety: feeling of satisfaction that occurs after eating which helps determine time
between meals
Other factors that determine intake: stress eating and responding to external cues (like
time of day or availability of appealing foods)
Hypothalmus: the control center (in the brain) that controls water balance, body
temperature, and appetite
Sources of energy in the British diet (adults)
6. The source of nutrition in china
% energy from fat
% energy from CHO
% energy from protein
89
91
93
97
89
91
93
97
89
91
93
97
Urban
21.4
29.7
32.0
32.8
65.8
58.0
55.0
53.3
12.8
11.8
12.3
12.9
Rural
18.2
22.5
22.7
25.4
70.0
65.6
65.2
62.1
12.1
11.4
11.7
11.7
Low
16.0
19.3
19.7
23.0
72.9
69.2
68.6
64.5
11.6
11.1
11.5
11.7
20.3
25.2
25.5
27.1
67.5
62.6
62.2
60.3
12.4
11.6
11.6
11.9
21.5
30.0
31.5
31.6
65.4
57.5
55.4
54.8
12.9
11.9
12.5
12.6
19.3
24.8
25.5
27.3
68.7
63.2
62.1
59.8
12.3
11.5
11.9
12.1
income
Middle
income
High
income
Total
A balanced diet in practice will mean:Eating more starchy foods such as bread,
potatoes, rice and pasta. Assuming these replace fat-containing foods, this will help to reduce
the amount of fat and increase the amount of fibre in the diet. Adding fat to these foods should
be avoided or kept to a minimum.
Eating more fruit and vegetables. It has been suggested that individuals aim for at least 5
portions of different fruits and vegetables a day (excluding potatoes). As long as extra fat is not
added to these foods, these changes will help to reduce fat intake, and increase intakes of fibre
and important nutrients such as vitamin C.
Choosing leaner cuts of meat and lower fat versions of dairy products will help to reduce the
amount of fat, particularly saturated fatty acids in the diet. Trimming fat, choosing cooking
methods that do not require added fat and eating smaller portions of high fat foods can all be
helpful.
Part 6
Water
Water, an inorganic compound, is classed as a nutrient because it
is essential to life.
However, it is not a source of energy like fats and carbohydrates,
nor does it build or repair body tissue as does protein. Instead, it
functions primarily as a solvent and transport vehicle for nutrients,
wastes, and body substances.
While we can live without food for weeks, or until we deplete our
stored carbohydrate and a large portion of our body protein, we
can’t survive without water for more than a few days (and we can’t
live without oxygen for more than a few minutes).
Water Functions
Carries nutrients and waste in the body
Maintains structure of molecules: proteins, glycogen, etc...
Participates in chemical reactions in the body
Acts as a solvent for most nutrients
Lubrication and cushioning of joints, spinal cord, and fetus (during
pregnancy)
Helps regulate body temperature
Maintains blood volume
Terms:
Intracellular fluid (胞内液): fluid within the cells
Interstitial fluid ( 空 隙 液 ): fluid between cells (component of
extracellular fluid)
Extracellular fluid (细胞外液): fluid outside of the cells
includes interstitial fluid, plasma, and the water in skins and bones
accounts for 1/3 of the body's water
Water balance in the body in a temperate
climate
Source
Water intake
(cm3/d)
Lose
Water loss
(cm3/d)
Food
1120
Urine
1300
drink
1180
Lungs
300
oxidation
of nutrients
280
Skin
920
Feces
60
Total
2580
Total
2580
Water Balance
WATER INTAKE (milliliters)
Beverages
1400
Solid Food
Cellular
Oxidation
Total
700
200
2300
WATER OUTPUT
Normal Ambient
Temperature
High Ambient
Temperature
Prolonged
Exercise
Urine
1400
1200
500
Feces
100
100
100
Perspiration
100
1400
5000
Skin
350
350
350
Respiratory
350
250
650
Tract
Total
2300
3300
6600
Deficiency
Loss of body water amounting to 10% of the body weight impairs work
performance and is associated with nausea, weakness, delirium (精神错
乱), and hyperthermia (过高热). Signs of dehydration include poor skin
turgor (肿胀), skin tenting (隆起)on the forehead, decreased urine output,
concentrated urine, sunken (凹陷的) eyes, dry mucous membranes in the
mouth and nose, orthostatic ( 直 立 的 ) blood pressure changes and
tachycardia (心动过速). Water losses exceeding 20% of body weight are
life-threatening.
Toxicity
Water intoxication may develop if large amounts of water are provided to
patients to replenish (补充) fluids lost with surgery, trauma (外伤) or
other conditions associated with fluid and electrolyte losses, especially
if compromised renal function or hormonal imbalances are also present.
The ensuing increase in intracellular fluid volume can cause swelling of
brain tissue accompanied by headaches, nausea, vomiting, muscle twitching,
convulsions, and even death.
Factors Affecting Availability
Water is not consumed in sufficient amounts by most individuals since
thirst does not develop until body fluids are depleted well below levels
required for optimal functioning. Mechanisms that trigger thirst
sensations are stimulated by increased osmolality or decreased
extracellular volume which are not detected until significant contraction
of plasma volume has occurred. Groups most vulnerable to dehydration,
infants, elderly adults, and athletes, are either not able to adequately
express thirst sensations or to detect them. With extreme heat and
excessive perspiration, thirst may lag behind actual water requirements.
To prevent dehydration, a minimum of eight cups of fluid is required daily
from beverages and foods.
Water Content of Selected Foods
91-100% WATER
80-90% WATER
70-79% WATER <69% WATER
Water, any type Soda Fruit juices
Peas
Potatoes
Milk
Non-carbonated
Frozen
Bread
Coffee
fruit drinks
yogurt
Pasta
Soup
Cantaloupe
Popsicle
Rice
Sports drink
Orange
Banana
Beef
Watermelon
Apple
Some fish
Poultry
Strawberries
Pear
Eggs
Nuts
Broccoli
Grapes
Casseroles Baked goods
Lettuce
Peach
Crackers
Tomato
Gelatin
Chips
Hydration (水合作用)
Dehydration
occurs when water output exceeds water
input. Signs of dehydration include dry skin, dry mucous
membranes, rapid heartbeat, low blood pressure, and weakness.
Water intoxication refers to the rare condition when body
water contents are too high.
Sources and Requirement
Sources:
water
- 100%
fruits and vegetables - 90-99%
fruit juices - 80-89%
pasta, legumes, beef, dairy - 10-60%
crackers, cereals - 1-9%
 oil - 0 % Amount needed: a 2,000 kcal (average) energy expenditure
person requires about 2-3 liters (7-11 cups) per day.
Vitamins
Part 7
Liu Fang
General Description and Common Characters of Vitamins
Vitamins are organic compounds of low molecule weight.
They are necessary for keeping natural physiological function, especially for intracellular
specific metabolism.
They can’t be synthesized in the body.
They are not the material of the tissue.
They exist in natural food in different form.
They can’t supply energy.
Vitamins are needed in just minute amounts and often do not undergo any digestive
process- they are simply absorbed “as is” in the intestine.
Many vitamins function as coenzyme and are necessary adjuncts to enzymes in catalyzing
specific metabolic processes in the body
Vitamins are consumed in their functions and must be obtained regularly from dietary
sources, since they are not produced in any appreciable amount in the body.
Solubility: determines classification
· Water soluble (hydrophilic): B vitamins and vitamin C
o
found in watery compartments of food
o
moves directly into the blood after being absorbed
o
can travel freely in the blood
o freely circulate in watery compartments of the body's cells
o
regulated and excreted when in excess by the liver easily – are less likely to have
toxic effects when ingested in large amounts.
Fat soluble (hydrophobic)
Vitamins A, D, E, and K
o
found in fats and oils of food
O
need fat for their absorption
o
carried through the lymph to the blood
o
many times require proteins for transport in the blood
o
trapped in cells associated with fat
o
less readily excreted - tend to stay in fat storage sites –can build up to toxic levels
with serious and potentially fatal results.
Bioavailability
This refers to the degree that any vitamin is utilised by our bodies and depends upon:
i. the concentration of the vitamin at the time of consumption. Water-soluble vitamins will
often leach out of the food if it is boiled in water.
ii. the actual form of the molecule present, since some forms are more easily converted
than others into the active form.
iii. the composition of the diet. This influence viscosity and pH and will have an effect on
the absorption of the nutrient by our bodies.
Any particular food source will have inherent variations in vitamin content, which in
animals is controlled by a biological control mechanism and the diet of the animal. In
fruits and vegetables, the concentration of nutrients will vary with maturity and is
determined by the rate of synthesis versus degradation.
Post harvest changes (including the slaughter of an animal) will often result in enzymes
that change the vitamin content of the food. Oxidative enzymes will reduce the
concentration of many vitamins and any labile vitamins will be lost with storage.
Many foods have nutrients additionally added to them (fortification) which has lead to
eradication of most vitamin deficiency diseases. This has been common in cereal based
products of which most of the vitamin content is lost once the initial seed coat of the bran
has been removed by milling.
一、VITAMIN A
INTRODUCTION
FUNCTION
DEFICIENCY
DISEASE PREVENTION
DISEASE TREATMENT
SOURCES
SAFETY
Structure of
Vitamin A
1. INTRODUCTION
Vitamin A is a generic term for a large number of related compounds. Retinol (视黄醇) and
retinal (视黄醛) are often referred to as preformed vitamin A . Retinal can be converted by the
body to retinoic acid (视黄酸), the form of vitamin A known to affect gene transcription. Retinol,
retinal, retinoic acid, and related compounds are known as retinoids （类维生素 A）.
Beta-carotene （胡萝卜素） and other carotenoids （类胡萝卜素） that can be converted
by the body into retinol are referred to as provitamin A- carotenoids. Hundreds of different
carotenoids are synthesized by plants, but only about 10 % of them are provitamin A carotenoids .
1) Lycopene
Lycopene, found in tomatoes appears to reduce the risk for breast, prostate and pancreas
cancer. However, further exploration and evaluation of the biological function of
lycopene alone or in combination with other chemical compounds present in foods is
required before claims can be made
2) Lutein (叶黄素)
A study at the Health Research Center in Salt Lake City, Utah, looked at 1,993 subjects ages
30 to 79 years who had been diagnosed with colon cancer, and a control group of 2,410 people
who did not have cancer. An inverse relationship between lutein intake and colon cancer was
found for all subjects, meaning those who ate lutein-containing foods had a lower risk of colon
cancer. Lutein is found in spinach, broccoli, lettuce, tomatoes, carrots, oranges and orange juice,
celery, greens and eggs.
3) Beta-carotene
Many epidemiological studies have found that people who have higher serum
beta-carotene levels have a lower risk of cancer, particularly lung cancer. However, as
noter above, two human intervention studies that used high-dose beta-carotene
supplements reported an increased risk for lung cancer among smokers.
Beta carotene is found in carrots and other orange and dark-green fruits and vegetables.
Warning: Beta-carotene supplements can increase cancer risk.
2. FUNCTION
Vision
Regulation of gene expression
Immunity
Growth and Development
Red blood cell production
1) Vision
The retina is located at the back of the eye. When light passes through the lens, it is sensed by the
retina and converted to a nerve impulse for interpretation by the brain.
2) Regulation of gene expression
Retinoic acid (RA) and its isomers act as hormones to affect gene expression and thereby
influence numerous physiological processes
3) Immunity
Vitamin A is commonly known as the anti-infective vitamin, because it is required for normal
functioning of the immune system . The skin and mucosal cells function as a barrier and form the
body's first line of defense against infection. Retinol and its metabolites are required to maintain
the integrity and function of these cells .
4) Growth and Development
Both vitamin A excess and deficiency are known to cause birth defects. Retinol and retinoic acid
(RA) are essential for embryonic development . During fetal development, RA functions in limb
development and formation of the heart, eyes, and ears . Additionally, RA has been found to
regulate expression of the gene for growth hormone
5) Red blood cell production
Red blood cells, like all blood cells, are derived from precursor cells called stem cells. These stem
cells are dependent on retinoids for normal differentiation into red blood cells. Additionally,
vitamin A appears to facilitate the mobilization of iron from storage sites to the developing red
blood cell for incorporation into hemoglobin, the oxygen carrier in red blood cells .
3. DEFICIENCY
Vitamin A deficiency and vision
Vitamin A deficiency and infectious disease
The Recommended Dietary Allowance (RDA)
1) Vitamin A deficiency and vision
Vitamin A deficiency among children in developing nations is the leading preventable cause
of blindness .
The earliest evidence of vitamin A deficiency is impaired dark adaptation or night blindness.
Mild vitamin A deficiency may result in changes in the conjunctiva (结膜) (corner of the eye)
called Bitot's spots.
Severe or prolonged vitamin A deficiency causes a condition called xeropthalmia (dry eye),
characterized by changes in the cells of the cornea (clear covering of the eye) that ultimately result
in corneal ulcers, scarring, and blindness .
2) Vitamin A deficiency and infectious disease
Vitamin A deficiency can be considered as a nutritionally acquired immunodeficiency disease.
Even children who are only mildly deficient in vitamin A have a higher incidence of respiratory
disease and diarrhea, as well as a higher rate of mortality from infectious disease, than children
who consume sufficient vitamin A . Supplementation of vitamin A has been found to decrease the
severity of and deaths from diarrhea and measles in developing countries, where vitamin A
deficiency is common .
3) RDA
RDA
Life Stage
Age
Infants
0-6 months
400 (1333 IU)
400 (1333 IU)
Infants
7-12 months
500 (1667 IU)
500 (1667 IU)
Children
1-3 years
300 (1000 IU)
300 (1000 IU)
Children
4-8 years
400 (1333 IU)
400 (1333 IU)
Children
9-13 years
600 (2000 IU)
600 (2000 IU)
Adolescents
14-18 years
900 (3000 IU)
700 (2333 IU)
Adults
Pregnancy
Males: mcg/day (IU/day)
19 years and older
18
years
and
900 (3000 IU)
700 (2333 IU)
-
750 (2500 IU)
younger
Pregnancy
19-years and older
-
770 (2567 IU)
Breastfeeding
18
-
1,200 (4000 IU)
-
1,300 (4333 IU)
years
and
younger
Breastfeeding
19-years and older
Females: mcg/day (IU/day)
4. DISEASE PREVENTION
Cancer
Lung cancer
Breast cancer
Cancer
Studies in cell culture and animal models have documented the capacity for natural and synthetic
retinoids to reduce carcinogenesis significantly in skin, breast, liver, colon, prostate, and other
sites . However, the results of human studies examining the relationship between the consumption
of preformed vitamin A and cancer are less clear.
DISEASE TREATMENT
Pharmacologic doses of retinoids
Retinitis pigmentosa (色素性视网膜炎)
Acute promyelotic leukemia (白血病)
Diseases of the skin
Pharmacologic doses of retinoids
It is important to note that treatment with high doses of natural or synthetic retinoids overrides (超
越) the body's own control mechanisms, and therefore carries with it risks of side effects and
toxicity. Additionally, all of these compounds have been found to cause birth defects. Women who
have a chance of becoming pregnant should avoid treatment with these medications.
Retinitis pigmentosa
Retinitis pigmentosa describes a broad spectrum of genetic disorders that result in the progressive
loss of photoreceptor cells (rods and cones) in the eye‘s retina. Early symptoms of retinitis
pigmentosa include impaired dark adaptation and night blindness, followed by the progressive loss
of peripheral（外围的）and central vision over time.
Acute promyelotic leukemia
Normal differentiation of myeloid（骨髓的）stem cells in the bone marrow gives rise to
platelets 血小板, red blood cells, and white blood cells, which are important for the
immune response. Altered differentiation of those stem cells results in the proliferation of
immature leukemic cells, giving rise to leukemia.
Diseases of the skin
Both natural and synthetic retinoids have been used as pharmacologic agents to treat disorders of
the skin. Etretinate and acitretin are retinoids that have been useful in the treatment of psoriasis 牛
皮癣, while tretinoin (Retin-A) and isotretinoin (Accutane) have been used successfully to treat
severe acne（粉刺）. Retinoids most likely affect the transcription of skin growth factors and their
receptors .
5. SOURCES
Everyday your body needs about 500-600 mg of vitamin A.
Sources of vitamin A can be divided in two groups, vegetable and animal foods. In animal
foods the vitamin A is present in a form called retinol, which is the active form of vitamin
A, and in vegetables it is present as provitamin A. You have to eat six times as much
provitamin A to get the same amount of vitamin A as in retinol.
It is easier for the body to take up vitamin A if the food is cooked and eaten together with
some fat or oil.
Animal food sources
Liver.
Fish liver oil.
Egg yolk.
Milk and milk products for example cheese.
Food with milk fat for examples margarine and butter.
Breast milk.
Small fish, with liver for example sardines .
Vegetable food sources
Dark green leaves for example spinach, cassava （木薯） and mustard.
Yellow and orange vegetables for example carrot, coloured yams, yellow squash (南瓜)
and sweet potatoes.
Yellow and orange fruits for example papaya 番木瓜果, apricots 杏 and mangoes (but not
citrus fruits).
Red palm oil.
Food
Cod liver oil
Fortified
Serving
1 teaspoon
breakfast 1 serving
cereals
Vitamin A,
Vitamin
Retinol,
Retinol,
RAE
A, IU
mcg
IU
1,350 mcg
4,500 IU
1,350 mcg
4,500 IU
150-230
500-767
150-230
500-767
mcg
IU
mcg
IU
Egg
1 large
91 mcg
303 IU
89 mcg
296 IU
Butter
1 tablespoon
97 mcg
323 IU
95 mcg
317 IU
Whole milk
1 cup (8 fl
68 mcg
227 IU
68 mcg
227 IU
134 mcg
447 IU
134 mcg
447 IU
ounces)
2% fat milk (vitamin 1 cup (8 fl
A added)
ounces)
fl
149 mcg
500 IU
149 mcg
500 IU
cup,
959 mcg
3,196 IU
0
0
cup,
385 mcg
1,283 IU
0
0
medium
466 mcg
1,555 IU
0
0
Spinach
1/2 cup, cooked
472 mcg
1,572 IU
0
0
Squash, butternut
1/2 cup, cooked
572 mcg
1,906 IU
0
0
Nonfat milk (vitamin A
1
cup
added)
ounces)
Sweet potato
1/2
(8
mashed
Carrot (raw)
1/2
chopped
Cantaloupe
1/2
melon
SAFETY
Toxicity
Safety in pregnancy
Drug Interactions
Toxicity
The condition caused by vitamin A toxicity is called hypervitaminosis A. It is caused by
overconsumption of preformed vitamin A, not carotenoids. Preformed vitamin A is rapidly
absorbed and slowly cleared from the body, so toxicity may result acutely from high-dose
exposure over a short period of time, or chronically from much lower intake
Toxicity
Daily doses exceeding 6,000 IU can produce growth retardation and urinary-tract
malformations of fetus 胎儿. Don't take megadoses (维生素等的)大剂量 .
A large body of observational epidemiologic studies has consistently demonstrated that
individuals who eat more fruits and vegetables, which are rich in carotenoids, and people
who have higher serum beta-carotene levels have a lower risk of cancer, particularly lung
cancer. In contrast to these observations, two studies that used beta-carotene supplements
reported an increased risk for lung cancer among smokers. The conclusion was that foods
rich in beta-carotene are protective but beta-carotene supplements are risky.
Vitamin A can be stored in the body. Continued high doses, therefore, can result in
toxicity. Signs of toxicity include itchy 使人发痒的 skin, headaches, nausea, and
diarrhea. During pregnancy, vitamin A toxicity may also cause birth defects. In addition,
excessive amounts of carotene, although not toxic, will cause the skin to turn orange.
Excess carotene is deposited in the skin.
Tolerable Upper Level of Intake (UL) for Preformed Vitamin A (Retinol)
UL in mcg/day (IU/day)
Age Group
Infants 0-12 months
600 (2,000 IU)
Children 1-3 years
600 (2,000 IU)
Children 4-8 years
900 (3,000 IU)
Children 9-13 years
1,700 (5,667 IU)
Adolescents 14-18 years
2,800 (9,333 IU)
Adults 19 years and older
3,000 (10,000 IU)
Safety in pregnancy
Although normal fetal development requires sufficient vitamin A intake, consumption of excess
preformed vitamin A (retinol) during pregnancy is known to cause birth defects. No increase in the
risk of vitamin A-associated birth defects has been observed at doses of preformed vitamin A from
supplements below 3,000 mcg/day (10,000 IU/day) .
Drug Interactions
Chronic alcohol consumption results in depletion of liver stores of vitamin A, and may
contribute to alcohol-induced liver damage. However, the liver toxicity of preformed
vitamin A (retinol) is enhanced by chronic alcohol consumption, thus narrowing the
therapeutic window for vitamin A supplementation in alcoholics .
二、Vitamin D
Introduction
Rickets was a common disease afflicting children in the eighteenth century.
Scientists explored the relationship between nutrition and irradiation of foods and found
that irradiated foods contained the nutrient that seemed to fight rickets
Research continued to determine how vitamin D worked in the body and scientists were
able to determine the process by which vitamin D regulates the amount of calcium in the
body .
Through extensive research, scientists isolated 3 forms of vitamin D, which made it
possible to synthesize the vitamin in large quantities .
Further investigations have shown that vitamin D plays many roles beyond maintaining
the body’s calcium levels. It is essential in maintaining health and preventing disease not
just during the crucial growing years of childhood but throughout life.
VD occurs naturally in only a few foods and that is also manufactured in the skin when a
precursor interacts with the short ultraviolet rays of the sun.
Status
A "vitamin" by definition is a substance regularly required by the body in small amounts but
which the body cannot make and is, therefore, required to be supplied in the daily diet. Technically
the molecular species classified as vitamin D is not really a vitamin because it can be produced by
exposure of the skin to sunlight .
Composition
There are two chemical forms of vitamin D, namely vitamin D2 and vitamin D3.
The natural form of vitamin D for animals and man is vitamin D3 that is produced in their
bodies from cholesterol and 7-dehydrocholesterol.
An alternative vitamin D2 is derived from the yeast sterol ergosterol (麦角固醇) by
chemical procedures.
The molecular structure of vitamin D is closely allied to that of the classical steroid
hormones.
The elements of the vitamin D endocrine system
include the following
In the skin, photoconversion of 7-dehydrocholesterol to vitamin D3
for dietary intake of vitamin D3. With the help of bile, VD3 will form colloid in the small
intestine and be absorbed into blood. Then it combines with α- globulin and be
transmitted to liver.
In the liver, the enzyme catalyze VD3 into 25-OH-D3, which is the major form of vitamin
D circulating in the blood compartment. and then it be transmitted to kidney.
Conversion by the kidney of 25(OH)D3
[functioning as an endocrine gland] to
produce the two principal dihydroxylated metabolites, namely
1a,25(OH)2D3 and
24R,25(OH)2D3.
Furthermore, vitamin-D-binding protein (DBP) take VD to all kinds of apparatus. Then
VD become functional.
Systemic transport of the dihydroxylated metabolites 1a,25(OH)2D3 and
24R,25(OH)2D3 to distal target organs.
Binding of the dihydroxylated metabolites, particularly 1a,25(OH)2D3, to a nuclear
receptor at the target organs followed by the subsequent generation of appropriate
biological responses.
VD mainly stored in fat tissues. Decomposed in liver. Excretion way is from gall.
Biological activity of different molecule weight
medicament
molecule formula
molecule
weight
antirachitis activity
(%)
VD2
C26H44O
396.66
100
VD3
C27H44O
384.65
100
VD4
C28H46O
398.68
75
VD5
C29H48O
412.71
<2
VD6
C29H46O
410.69
<1
VD7
C28H46O
398.68
10
Physiological Action
Promote calcium be absorbed in small intestine.
. Accelerate calcium and phosphor’ absorb in kidney
Boost the absorb of calcium and phosphor in bone, strong the teeth.
Adjust the transcription.
Keep the balance of calcemia.
Prevent the loss of amino acid in kidney
Promote calcium be absorbed
in small intestine.
1α,25-(OH)-D3 induce the synthesize of calcium binding protein. It’s the carrier of
calcium.
This protein can make calcium easily enter small intestine.
The calcium is transported to blood circle
Accelerate calcium and phosphor’
absorb in kidney
25-(OH)2D3 has direct effect on kidney. it enlarge
the absorb of calcium and phosphor
Reduce the probability of rachitis
Boost calcify of bones tissues
Adjust the gene transcription.
The regulation of gene transcription by 1a,25(OH)2D3 is known to be mediated by
interaction of this ligand with a nuclear receptor protein, termed the VDR.
The tissue distribution of the VDR is known to occur in over 30 different cell types.
In addition ,1a,25(OH)2D3 and the VDR are known to regulate the independent
transcription of numerous proteins.
Keep the balance of calcemia. 钙血(症)
There is vitamin D internal secretion system in our body.
1α,25-(OH)-D3 is the main adjust gene，it can adjust the calcemia level.
Regulating blood calcium levels is important. When there is too little calcium in the blood,
soft-tissue cells--especially nerves and muscle--shut down, sending the body into
convulsions;
when there is too much calcium in the blood, organs calcify and eventually cease to
work.
For human patients who had lost their parathyroid glands or their kidneys and could no
longer regulate the level of calcium in their blood.
the newly synthesized vitamin D hormone, when given with plenty of calcium, had a
dramatic effect, curing them of convulsions and chronic bone disease.
The new function of VD
VD may update immunity, have active effect on the treatment of immunity illness.
Some experiment on mice has showed that VD will induce some cells that lead to
diabetes to death.
VD Induce the cell differentiation, and can be used to cure tumour.
VD Will reduce the sensitivity to multiple scleross, which is a kind of self immunity
disease.
May inhibit the generation of gene that would lead to arthritis
VD as hormone
vitamin D hormone in the nucleus of cells that were not part of the classical calcium
maintenance system including the brain, lymphocytes (infection fighting white blood
cells), skin, and malignant tissues.
adding the hormone to immature malignant leukemia cells caused the cells to differentiate,
mature, and stop growing.
However, the amount of vitamin D hormone needed to stop the runaway growth of tumors and
cancers has so far proved too toxic for human use,
vitamin D hormone also seemed to play a part in modulating the immune system.
In 1993, S. Yang and other researchers in DeLuca's laboratory found that rats given a
large dose of vitamin D hormone were protected from the inflammation normally
associated with wounds and chemical irritants.
More developed is vitamin D hormone's effect on psoriasis.
a Japanese research team demonstrated that 1,25-dihydroxyvitamin D3 can inhibit skin
cell growth.
Clinical Practice
Antitumour function.
Therapy of psoriasis.
Treatment of rachitis.
Curing of immunity deficiency for children.
Treatment of hypertension.
Treatment of tuberculosis
Relation between VD and calcium
Calciferol as hormone will improve plasma, calcium and phosphor level.
Also VD will change the permeation of mucous membrane.
After absorb, VD is not active. in liver it will turn into calciferol.
Accelerate calcium salt depositing on bone.
vitamin D can actually remove calcium from bones when it is needed by the body.
1,25-dihydroxyvitamin D3, the active form of vitamin D, was reclassified as a hormone
that controlled calcium metabolism.
A hormone is a chemical substance produced by one organ and then transported in the
bloodstream to a target organ, where it causes a specific biological action.
1,25-dihydroxyvitamin D3 is produced by the kidneys and that its secretion by the
kidneys is followed by its build up in cell nuclei of the intestine, where it regulates
calcium metabolism.
as the level of calcium in the diet rises, the amount of active vitamin D hormone in the
body falls
a hormone produced by the parathyroid gland is critical to maintaining adequate levels of
vitamin D hormone in the blood.
When calcium is needed, the parathyroid gland sends the parathyroid hormone to the
kidneys to trigger production of vitamin D hormone.
When calcium intake is too small to support normal functions, both vitamin D and the
parathyroid hormone trigger a process in which stored calcium is mobilized from the
bones.
Boy suffering from rickets
eficiency of VD
Deficiency of VD will reduce the absorb of calcium and phosphor.
Shortage of VD may increase the probability of rickets to baby.
For adult, less will lead to osteomalacia 骨软化
and osteoporosis.骨质疏松症
.Furthermore, lack of will produce extremity convulsion
Cause of VD deficiency
Short of sun.
Deficiency of outdoor activity.
Lack of VD in dietary.
Some babies grow too quick.
The illness in stomach, intestines, courage will affect the incorporation and utilization
of calcium and VD.
Some medicines have negative effect on VD absorb
rickets of vitamin D deficiency
A common illness happens to baby between 3 month and 2 year’ old.
It mainly caused by vitamin D deficiency
It may cause pathological changes in growing bone.
Muscle may became flab, also the nerve will less excited.
Worse more, it may cause digest and caidiopulmonary illness.
Excess of VD
Too much VD will cause toxicosis
Large dose VD may lead to ill reaction. Including anorexia, fatigue, spew, even insanity.
It can also cause impair to sight.
Too much VD is harmful for kidney.
It will destroy vein.
Others include anemia, weight loosing, etc
The cause of toxicosis
Inject too much VD, especially after have taken orally
Long time of VD taking, because of the ignorance of the toxicosis of VD
Too much lead to calcium’ decompensate.
The treatment of toxicosis of VD
Stop the take of VD and calcium.
Avoid the sun
Have low calcium dietary.
If worse, you must see doctor
Daily recommendation
Sort
age
VD(mg)
Baby
0-1
10
Child
1-10
10
Adult
10
Pregnant woman
10
nannie
10
Resources
Name
Content
Name
Content
(IU/100g)
Name
(IU/100g)
Content
(IU/100g)
Butter
35
Fishing rod
8000-30000
Sardine
1150-1570
Cream
50
Liver of ox
9-42
Turbot
44
Creamery
0.3-0.4
Liver
17-20
Salmon
154-550
Menhaden
315
of
sheep
Egg
50-60
Liver o f pig
44
Shrimp
150
Liver
50-67
of
chicken
VD production
When ultraviolet radiation have effect on ergosterol, we will get rough VD2
By chemical methods, we can synthesize VD.
The first method
Ergosterol is coming from high epiphyte fruit body.
It can be made from fat.
By proper incubation and intense aeration and add some phosphor to low nitrogen
contenting substrate.
plasmolysis,and breaching cytoplasmic membrane.
Then distill the fat.
The second method
Using cholesterin or acetate to product .
By brominzed reaction, and catalysis by base to conform double bond.
By soap treatment and photochemical reaction, we’ll get pro- VD.
Rearrangement of pro- VD, it is VD3 .
Conclusion
As we enter the twenty-first century, we recognize that the basic scientific research done
in the previous two centuries has not only untangled the workings of the elusive vitamin
D hormone, but also and has given us ways to protect the health of both adults and
children.
Researchers are pursuing many new applications for vitamin D, but its role in building and
maintaining bone continues to be an important health issue, especially among middle-aged and
older adults
三、Vitamin E
The background
•Vitamin E was discovered in 1922 when Evans HM et al. described a "substance X" that was
essential to maintain rat fertility.
•Pure -tocopherol was isolated from wheat-germ oil in 1936 (Evans HM et al., J Biol Chem 1936 ),
the structure was given in 1938 (Fernholz E, J Am Chem Soc 1938 ), and its first synthesis
(all-racemic 外旋的 form) was realized at the same year (Karrer P et al., Helv Chim Acta 1938,).
• Tocotrienols (三稀 VE) were prepared for the first time in 1963 (Schudel P et al., Helv Chim Acta
1963 ) and synthesized in 1976 (Scott JW et al., Helv Chim Acta 1976).
What is it
Tocopherols are oily yellow liquids, water insoluble, heat and acid stable, that deteriorate
with exposure to alkali, light, oxygen, and on contact with iron and lead
•The structure is that of the tocopherols. These are methylated derivatives of tocol. There
are eight different forms. Of these, four occur naturally in foods :
o
alpha - tocopherol, C29H50 O2 is 5,7,8,-trimethyltocol - strongest vitamin E activity.
obeta - tocopherol C28H48 O2 is 5,8,-trimethyltocol
ogamma - tocopherol C28H48 O2 is 7,8,-trimethyltocol
odelta - tocopherol C27H46 O2 is 8,-trimethyltocol
The structure
Each form has its own biological activity. Alpha-tocopherol is the most active form of vitamin
E in humans, and is a powerful biological antioxidant.
The active sequence is alpha – tocopherol, beta - tocopherol, gamma -tocopherol, delta –
tocopherol.
What foods provide vitamin E
Vegetable oils, nuts, and green leafy vegetables are the main dietary sources of
vitamin E. Fortified cereals are also an important source of vitamin E in the
United States. The table of selected food sources of vitamin E suggests foods
that contain vitamin E.
In 1990, 62.5 percent of the vitamin E in the diets of Americans came from fats and oils, and
12.4 percent came from meats, poultry, fish, legumes, nuts, and soy.
What is the Recommended Dietary Allowance for vitamin E for adults?
The Recommended Dietary Allowance (RDA) is the average daily dietary
intake level that is sufficient to meet the nutrient requirements of nearly all
(97-98%) healthy individuals in each life-stage and gender group (5). The 2000
RDAs for vitamin E (5) for adults, in milligrams (mg) and International Units
(IUs) are:
Life-Stage
Men and
Women
Ages 19+
15 mg* or 22 IU
All ages
Pregnancy
Lactation
15 mg* or 22 IU
19 mg* or 28 IU
*1 mg alpha-tocopherol equivalents = 1.5 IU
RDA
The RDA for vitamin E is based on the alpha-tocopherol form because it is the
most active, or usable, form (5, 6). Unlike other vitamins, the form of
alpha-tocopherol made in the laboratory and found in supplements is not
identical to the natural form, and is not quite as active as the natural form.
a 2000 Institute of Medicine (IOM) report on vitamin E states that
intake estimates of vitamin E may be low because energy and fat intake
is often underreported in national surveys and because the kind and
amount of fat added during cooking is often not known. The IOM states
that most North American adults get enough vitamin E from their
normal diets to meet current recommendations.
The distribution in body
Storage of vitamin E is limited. vitamin E is briefly stored in the liver but only at small quantities.
Adipose tissue and the adrenal glands (肾上腺) do store vitamin E as well. The adipose tissue
slowly accumulates vitamin E and then in time slowly releases it as well.
Metabolism
• Vitamin E requires the presence of bile for absorption.
• At normal levels of intake only 20-30% of dietary vitamin E is absorbed. This percentage
decreases with increased dosage.
Vitamin E is stored in high amounts in the pituitary gland (脑下垂体) and the adrenals.
• There is no correlation between serum levels and Vitamin E stores. A serum peroxide value
can give an indirect status.
Metabolism
Previously, numerous health authorities have recommended use of Vitamin E supplements,
made in their natural form from soybeans, because of the difficulty of receiving sufficient VE
intake from dietary sources.
The benefit of vitamin E
Anti-Oxidant:
Vitamin E protects cell membranes, especially in the lungs and red blood cells. It particularly
protects fatty acids against oxidative damage caused by various pollutants, peroxides, and free
radicals formed during metabolic processes. It aids in the prevention of lipofuscin 脂褐质, an
oxidized fat that has been implicated in the aging process.
Evidence has been presented that supplemental vitamin E along with vitamin C may greatly
inhibit the formation of mutagens in the feces, thus preventing the formation of polyps 息肉 and
cancer. Vitamin E may protect the liver and the rest of the body against environmental pollutants
such as ozone and other constituents of smog. People receiving chemotherapy or radiation can
also be protected with additional vitamin E supplementation.
Vitamin E works synergistically with other antioxidant nutrients including selenium,
vitamin C, B-carotene and others to quench free radicals, peroxides and other
potentially harmful substances. Vitamin E can spare other antioxidants and vice
versa 反之亦然. Red blood cells are particularly susceptible to oxidative damage
because of their high oxygen tension. Sickle cell 镰状细胞 anemia has been
successfully treated with vitamin E.
Other antioxidant functions
Nerve and muscle function:
vitamin E is vital for the protecting of nerve and muscle cell function. In children
who had a lack of bile (cholestasis 胆汁郁积) to absorb fats and vitamin E it was
found that vitamin E was able to protect against damage to Schwann 施沃恩 cells,
dorsal root ganglia 后根神经 and muscle cells. In adults who are deficient in vitamin
E it will result in peripheral nerve 末稍神经 degeneration.
Premature infants
develop retrolental 眼晶状体后面的 fibroplasia 纤维素增生 or damage occur to the
retina due to their high oxygen exposure. Vitamin E can protect against this damage.
In addition vitamin E can protect the lens of the eye from oxidation, cross linking
of the collagen fibers and formation of cataracts 白内障.
Muscular dystrophy 肌肉萎缩症
The type diseases have been treated with vitamin E with only anecdotal(轶事一
样的)success.
Cholesterol peroxidation:
It can occur when vitamin E is deficient. In particular LDL cholesterol yields epoxycholesterols 环氧的 which have been implicated in cardiovascular disease.
Other function of vitamin E
Anti-inflammatory effects:
vitamin E inhibits the enzyme lypoxygenase, an enzyme responsible for the
formation of leukotrienes which cause inflammation. This can be useful in the
treatment of asthma 哮喘 and other inflammatory conditions such as arthritis 关节
炎.
Anti-platelet 血小板 aggregation effects:
vitamin E at higher doses has been shown to increase production of prostaglandin
前列腺素 I2 which inhibits platelet stickiness.
Needed for normal reproduction
Some unproven theories about the powers of vitamin E to improve sexual
performance, prevent aging.
In the experimental animals, it is needed for normal reproduction.
When can vitamin E deficiency occur?
Vitamin E deficiency is rare in humans. There are three specific situations
when a vitamin E deficiency is likely to occur. It is seen in persons who
cannot absorb dietary fat, has been found in premature, very low birth weight
infants (birth weights less than 1500 grams, or 3 1/2 pounds), and is seen
in individuals with rare disorders of fat metabolism. A vitamin E deficiency
is usually characterized by neurological problems due to poor nerve
conduction.
The signs and symptoms of Vitamin E deficiency are dry skin, easy bruising,
decreased clotting time, eczema 湿疹, elevated indirect bilirubin 胆红素,
psoriasis 牛皮癣, elevated heavy metals, Pre-Menstrual Syndrome (PMS 月经
前不快症状), cystic fibrosis 囊肿性纤维化, sickle cell anemia, cataracts
白内障, fibrocystic 纤维囊性的 disease, benign 良性的 prostatic hypertrophy
肥大, poor wound healing, growing pains.
What is the health risk of too much vitamin E?
The health risk of too much vitamin E is low. A recent review of the safety
of vitamin E in the elderly indicated that taking vitamin E supplements for
up to four months at doses of 530 mg or 800 IU (35 times the current RDA)
had no significant effect on general health, body weight, levels of body
proteins, lipid levels, liver or kidney function, thyroid hormones, amount
or kinds of blood cells, and bleeding time.
四、Vitamin K
Vitamin K is produced by naturally occurring intestinal bacteria, but can
also be found in many foods. It is required for the formation of four protein
substances needed in blood coagulation known as K-dependent clotting
factors.
The one present in the highest concentration in blood plasma is prothrombin
凝血素. It is converted to thrombin 凝血酶, which then converts fibrinogen
纤维蛋白原 in the blood to fibrin, the key substance in blood clothing
Deficiency
The main result of a vitamin K deficiency is problems with the coagulation
(clotting) of blood. It can occur in premature infants who haven't built up
adequate vitamin K stores.
A deficiency can be brought on by long-term antibiotic therapy which destroys
gut bacteria, halting the synthesis of vitamin K.
Toxicity
There have been no reports of vitamin K toxicity from natural food sources.
There have been reports, however, that a synthetic version (menadione 甲
萘醌) can cause anemia and jaundice 黄疸
Vitamin K crystals under polarized light
Sources:
Green leafy vegetables such as spinach and cabbage, liver, soybeans and supplements are
good sources of vitamin K. The vitamin is also synthesized in the human intestinal tract
by certain bacteria.
Natural vitamin K from plants is known as phylloquinone 叶绿醌. The vitamin K made
by bacteria is called menaquinone 甲基萘醌类.
Recommended Intakes
RDAs:
70-80 µg /day for adult males
60-65 µg /day for adult females
55 µg /day for children ages 15-18
45 µg /day for children ages 11-14
30 µg /day children ages 7-10
20 µg /day children ages4-6
15 µg /day children ages1-3
10 µg /day infants ages six months - one year
5 µg /day infants from birth - six months
五、 VITAMIN B1 (THIAMINE)
Introduction
It is a white, water-soluble crystalline solid. its molecule has a complex structure which include
an amino(-NH2) group and a hydroxyl group
Because thiamine is soluble in water,as much as 50% may be lost when vegetables are
boiled .Thiamine decomposes on heating though it is fairly stable at the boiling point of water
and little loss occurs at this temperature in acid condition. In neutral or alkaline conditions
breakdown is more rapid.
Dietary Source
Limited quantities of thiamine can be found in most foods, but large amounts of this vitamin
can be found in pork and organ meats. Other good dietary sources of thiamine include
whole-grain or enriched cereals and rice, wheat germ, bran, brewer's 啤酒制造者
yeast, and blackstrap molasses 赤糖糊.
Function
Thiamin is involved in releasing energy from carbohydrate, alcohol and fat. The effective use of
carbohydrates is dependent on this vitamin which functions as the coenzyme thiamin
pyrophosphate 焦 磷 酸 盐 , or cocarboxylase 焦 磷 酸 硫 胺 素 , in the oxidation of glucose.
Hydrochloric acid (stomach acid) is necessary for thiamin absorption.
Thiamine may enhance circulation, helps with blood formation and the metabolism of
carbohydrates.
It is also required for the health of the nervous system and is used in the biosynthesis of a number
of cell constituents, including the neurotransmitter acetylcholine and gamma-amino butyric acid
(GABA). It is also great for the brain and may help with depression and assist with memory and
learning.
In children it is required for growth and has shown some indication to assist in arthritis, cataracts
as well as infertility.
Deficiency
A deficiency will result in beriberi 脚气病, and minor deficiencies may be indicated with extreme
fatigue, irritability, constipation, edema 浮肿 and an enlarged liver. Forgetfulness, gastrointestinal
disturbances, heart changes, labored breathing and loss of appetite may also be experienced.
With too little thiamine around a person may also experience nervousness 神经过敏, numbness 麻
木 of the hands and feet, pain and sensitivity, poor coordination, tinglingsensations 麻刺感, weak
and sore muscles, general weakness and severe weight loss
Uses
Beriberi
The most important use of thiamine is in the treatment of beriberi, a condition caused by a
deficiency of thiamine in the diet. Symptoms include swelling, tingling or burning
sensation in the hands and feet, confusion, difficulty breathing (from fluid in the lungs),
and uncontrolled eye movements (called nystagmus 眼球震颤).
Wernicke-Korsakoff syndrome
Wernicke-Korsakoff syndrome is a brain disorder caused by thiamine deficiency.
Replacing thiamine alleviates the symptoms of this syndrome. Wernicke-Korsakoff is
actually two disorders in one:
(1) Wernicke's disease involves damage to nerves in the central and peripheral nervous
systems and is generally caused by malnutrition (particularly a lack of thiamine)
associated with habitual alcohol abuse, (2) Korsakoff syndrome is characterized by
memory impairment with various symptoms of nerve damage. High doses of thiamine
can improve muscle in coordination and confusion associated with this disease, but only
rarely improves the memory loss.
Heart failure
Thiamine may be related to heart failure in two ways. First, low levels of thiamine may
contribute to the development of congestive 充血的 heart failure (CHF). On the flip side,
people with severe heart failure can lose a significant amount of weight including muscle
mass (called wasting or cachexia) and become deficient in many nutrients. It is not known
whether taking thiamine supplements would have any bearing on the development or
progression of CHF and cachexia 恶疾. Eating a balanced diet, including thiamine, and
avoiding things that deplete this nutrient, such as high amounts of sugar and alcohol,
seems prudent, particularly for those at the early stages of CHF.
Dosage
1、Pediatric
Newborns to 6 months: 0.2 mg (adequate intake)
Infants 7 months to 1 year: 0.3 mg (adequate intake)
Children 1 to 3 years: 0.5 mg (RDA)
Children 4 to 8 years: 0.6 mg (RDA)
Children 9 to 13 years: 0.9 mg (RDA)
Males 14 to 18 years: 1.2 mg (RDA)
Females 14 to 18 years: 1 mg (RDA)
2、Adult
Males 19 years and older: 1.2 mg (RDA)
Females 19 years and older: 1.1 mg (RDA)
Pregnant females: 1.4 mg (RDA)
Breastfeeding females: 1.5 mg (RDA)
The dosage is the Recommended Dietary Allowance (RDA), but be aware that this dosage is the
minimum that you require per day, to ward off serious deficiency of this particular nutrient. In the
therapeutic use of this nutrient, the dosage is usually increased considerably, but the toxicity level
must be kept in mind.
Toxicity and symptoms of high intake
Thiamine toxicity is uncommon; as excesses are readily excreted, although long-term
supplementation of amounts larger than 3 gram have been known to cause toxicity
Digestion
It is water-soluble vitamin which exist in cells in the form of combined-protein, and in the
process of the breakdown of cells and the digestion of protein, these
combined-compounds are decomposed and set thiamine free
Absorption
It is absorbed in intestine by passive diffusion when the concentration is high, on the contrary,
by initiative transportation
Cautions
Antibiotics, Tetracycline 四环素
Vitamin B1 should not be taken at the same time as the antibiotic tetracycline because it
interferes with the absorption and effectiveness of this medication. Vitamin B1 either
alone or in combination with other B vitamins should be taken at different times from
tetracycline taken. (All vitamin B complex supplements act in this way and should
therefore be taken at different times from tetracycline.)
Water Soluble
六、Riboflavin---Vitamin B2
Functions
Participates in enzymatic energy release of carbohydrate, fat and protein.
Riboflavin is important for flavin adenine dinucleotide (FAD) and flavin mononucleotide
(FMN). These compounds help regulate cellular metabolism through oxidation-reduction
reactions.
promotes vision .
promotes skin health .
Deficiencies
Eye problems, weakness, sore throat, skin disorders
Toxicity：
None known. Possible interference of other B vitamins.
Recommended Intakes
RDAs:
1.7 mg/day for adult males
1.3 mg/d for adult females
additional 0.3 mg/d during pregnancy
additional 0.5 mg/d during lactation
0.4 mg/d for infants
Food Sources
Milk / dairy, dark green vegetables, eggs, yogurt, enriched breads/cereals, liver, meat.
七、Niacin---Vitamin B3
Nicotinic acid, Nicotinamide
Functions
Niacin is a water-soluble vitamin that participates in more than 50 metabolic functions .
Important constituent of two coenzymes, nicotinamide adenine dinucleotide (NAD) and
nicotinamide adenine dinucleotide phosphate (NADP) in enzymatic energy release;
promotes health of nerves, skin and digestive system
Deficiencies
Pellagra 糙皮病, dermatitis on body parts exposed to sun, diarrhea, dementia, loss of
appetite, weakness, mental confusion, irritability, fatigue
One symptom of pellagra is a thickening, peeling, and discoloration of the skin
Toxicity
High doses of niacin can cause flushing, itching 痒的, vomiting, abdominal cramps 抽筋,
diarrhea, weakness, lightheadedness, headache, fainting, sweating, high blood sugar, high
uric acid, heart rhythm disturbances, and jaundice 黄疸.
Recommended Intakes
RDAs: NE = niacin equivalents
13-19 NE/day for adults
additional 2 NE/day during pregnancy
additional 5 NE/day during lactation
5-6 NE/day for infants
9-13 NE/day for children, ages 1-10
Food Sources
Yeast, meats, eggs, poultry, liver, cereal, legumes, seeds, milk, green leafy vegetables, fish,
nuts
Caution
Niacin is often prescribed for reducing serum cholesterol. Common doses are over 100
times the recommended daily dietary amount. At such a level, niacin is acting as a drug
and not a vitamin. Persons using this much niacin should be monitored by a physician.
Smoking can impair niacin absorption and thus smokers may require more than
non-smokers.
八、Vitamin B6
Function
Vitamin B6 consists of several compounds including, pyridoxal 吡哆醛, pyridoxamine
and pyridoxine.
These compounds are transformed in the liver, red blood cells and other tissues into
important coenzymes required for the building up and breaking down of proteins,
carbohydrates and fats.
It is essential for protein metabolism, and for the formation of haemoglobin - the pigment
in the blood that carries oxygen round the body.
Health Issues
A vitamin B6 deficiency does not produce an easily recognized disease. Symptoms can
include dermatitis, convulsions, anemia and excitability.
Sources
Vitamin B6 is found in the following foods:
Poultry
Fish
Kidney
Pork
Egg
Brown rice
Soy beans
Oats
Nuts
Recommended Intakes
RDAs:
2.0 mg/d for adult males, ages 15+
1.6 mg/d for adult females, ages 15+
2.2 mg/d during pregnancy
2.1 mg/d during lactation
1.7 mg/d for male children, ages 11-14
1.4 mg/d for female children, ages 11-14
1.4 mg/d for children, ages 7-10
1.1 mg/d for children, ages 4-6
1.0 mg/d for children, ages 1-3
0.6 mg/d for infants six months to one year
0.3 mg/d for infants birth to six months .
Pantothenic Acid 泛酸
Function
Health Issues
Pantothenic acid is considered a member of the B group of vitamins. It is important for
normal tissue metabolism and is involved with the synthesis of fatty acids, cholesterol and
sterols. It is found in two enzymes - coenzyme A and acyl-carrier-protein (ACP).
Sources
Pantothenic acid is found in a wide variety of plant and animal foods, including in yeast,
and eggs.
Recommended Intakes
Estimated Safe and Adequate Intake:
4-7 mg/day for adults
4-7 mg/d for children ages 11+ years
4-5 mg/d for children 7-10 years
3-4 mg/d for children 4-6 years
3 mg/d for children six months to 3 years
2 mg/d for infants birth to six months
十、Vitamin B12
Function
Vitamin B12 (cobalamin) is a group of compounds essential for several enzyme systems
involving the transfer of one-carbon units for the methylation of homocysteine 同型半胱
氨酸.
Vitamin B12 affects the growth and repair of all cells, particularly nerve cells.
It also plays a role in the activation of amino acids during protein formation. In
combination with folic acid, it is necessary for the syntheses of DNA and for
maintaining the myelin sheath 髓鞘 that surrounds nerve cells to speed up nerve impulse
transmission.
Sources:Vitamin B12 is found in meats, liver, fish, poultry and milk.
Health Issues: Vitamin B12 deficiency can result in anemia, fatty liver, and peripheral
nerve degeneration. Many older people suffer from pernicious anemia 恶性贫血 that can
be alleviated with regular injections of this vitamin.
Recommended Intakes
RDAs: (Strict vegetarians should consult a physician or RD for B12 supplements)
2.0 µg/day for adolescents and adults
2.2 µg/d during pregnancy
2.6 µg/d during lactation
1.4 µg/d for children, ages 7-10
1.0 µg/d for children, ages 4-6
1.0 µg/d for children, ages 1-3
0.5 µg/d for infants six months to one year
0.3 µg/d for infants birth to six months
十一、Biotin
Function
Biotin is a component of an enzyme acetyl CoA, which is required in metabolic reactions
where carbon dioxide is transferred to other molecules.
Biotin is involved in the metabolism of fatty acids and amino acids - essential for
carbohydrate, fat and protein metabolism. It is involved in the conversion of protein and
carbohydrate into fat. When the level of carbohydrates in the body is low, biotin helps
maintain normal blood glucose levels from fat and protein sources.
Health Issues:
Biotin deficiencies are rare but can result in anorexia 厌食, nausea 恶心 and depression. Large
intakes of raw egg whites (containing avidin 抗生物素蛋白) may induce a deficiency
Sources:
The diet is seldom short of biotin. Good sources include milk, eggs, liver and yeast
Recommended Intakes
Estimated Safe and Adequate Intake:
30-100 µg/day for adults
30 µg/d for children ages 7-10 years
25 µg/d for children 4-6 years
20 µg/d for children 1-3 years
15 µg/d for children six months to 1 year
10 µg/d for infants birth to six months
十二、Folate (Folic acid or Folacin)
Cell division. This process requires folate to occur
Function
Folic (folacin) is a component of tetrahydrofolic acid, which is involved in the transfer of
one-carbon groups - i.e. the transfer of methyl groups to help resynthesize methionine
from homocysteine and to form choline.
Folic acid is also important in the synthesis of purines and pyrimidines.
Sources: Good sources of folic acid include liver, leafy vegetables (spinach) legumes,
nuts and cereal grains
Health Issues: Folic acid deficiency can cause megaloblastic 有巨胚红血球的 anemia
(defective DNA synthesis resulting in abnormal red blood cells especially in bone
marrow), diarrhea, fatigue and depression. A sufficient intake of folic acid is especially
important during pregnancy for normal cell development of the foetus.
Recommended Intakes
RDA:
400 µg/day for adults
400 µg/d for adult females of childbearing age
600 µg/d during pregnancy
500 µg/d during lactation
150 µg/d for children ages 11-14 years
100 µg/d for children ages 7-10 years
75 µg/d for children 4-6 years
50 µg/d for children 1-3 years
35 µg/d for children six months to 1 year
25 µg/d for infants birth to six months
十三、Vitamin C
This is a white solid and behaves like an acid (having a sharp taste associated with acids).
Vitamin C is highly polar so it is readily soluble in aqueous solutions.
It is optically active and dextrarotatory(右旋的).
Opening of the lactone 内酯 ring irreversibly 不可逆 destroys vitamin C activity and
results in loss of its nutritional value. However, this may result in the production of
flavour compounds or their precursors, and it may also participate in non-enzymatic
browning reactions (Maillard reaction).
Function
Vitamin C (Ascorbic Acid) is an antioxidant 。 The oxidation-reduction reaction between
ascorbic acid and dehydroascorbic acid is reversible, if dehydroascorbic acid is further
oxidized, it no longer has vitamin C activity, this reaction is not reversible.
is involved in the synthesis of protein collagen which is necessary for skin, connective
tissue, the bone matrix and tooth dentine 牙质.
Help maintain normal elasticity 弹性 and strength of blood vessels and capillaries.
Influence formation of hemoglobin. Aids in the absorption of iron.
Protect the body against infections and bacterial toxins
Health Issues
A deficiency of vitamin C can result in the disease scurvy 坏血病- a common illness
among mariners who did not have a source of fresh fruits and vegetables. Symptoms
include fatigue, loss of appetite, retarded wound healing and fragile capillaries (bleeding
gums 齿龈). Loose teeth and bone joint diseases are also common.
High daily intake of vitamin C (1000mg or more) has been recommended to lower blood
cholesterol and prevent colds. These claims have yet to be proven.
Toxicity
Nausea, diarrhea, red blood cell damage, nosebleeds, abdominal cramps.
Recommended Intakes
RDA: Not an international agreement - 60 mg per day for male and female in the US; 30
mg per day in Canada and UK.
NEW DRIs:
75 mg for adult women
90 mg for adult men
Old RDAs:
60 mg for adults
75-95 mg for pregnant and lactating women
35-40 mg/day in children, ages 1-3
The requirement in smokers may be increased to 100 mg/day.
Sources
Vitamin C is easily destroyed by food processing (oxidation) especially heat. Good
sources of vitamin C are jujube 枣(highest content in fruits), citrus fruits, papaya, green
peppers, broccoli, brussels sprouts, cauliflower 花椰菜, cabbage. Potatoes also contain
small amounts of vitamin C. Animal products, milk and cereals are poor sources. n nature,
vitamin C is synthesised from glucose in a number of steps, involving oxidation and
reduction.
If you decide to take vitamin supplements:
Doses larger than 500 mg per day are quickly excreted in the urine and therefore a waste
of money.
Rinse the mouth after using chewable vitamin C because it is acidic and can erode tooth
enamel 釉.
Be aware of the vitamin C you are getting from fruits, fortified juices and cereals and
count that into your vitamin C total for the day.
十四、Choline
Function: Choline is generally listed as a vitamin. It is considered as essential, mainly for
infants and is involved in lipid transport, cell membrane structures and brain tissue. It
functions in the transmission of nerve impulses (acetyl choline). It is thought that adults
can synthesize sufficient amounts of choline (possibly by intestinal bacteria) so it is not a
vitamin in a strict sense.
Sources: Good sources of choline are lecithin, seed oils, liver and egg yolks.
Health Issues: Choline has been used to treat Alzeimer's disease and fatty liver.
Part 8 Minerals
Introduction
 Minerals are inorganic (do not contain Carbon)
 1.Classifications
Major Minerals: essential mineral nutrients found in the human body in amounts larger
than 5 grams (≥1/10000).
Trace Elements: essential minerals found in the human body in less than 5 grams (≤
1/10000).
 These include all the nutritionally important chemical elements obtained from the
macronutrients excluding C, H, N, O and S. They are considered essential in that if
their source of exposure were removed, there would be a consistent and reproducible
impairment of some physiological activity.
 Minerals are found in many different chemical forms, known as species and these
include complexes, chelates and free ions (especially group 1 and 17 elements). Free
ions are highly water soluble and so are easily absorbed by our bodies. They tend to
have low affinities for other ligands.
 Minerals are essentially indestructible since they are not affected by heat, light,
oxidizing agents or extremes in pH, but they may be extracted from food by leaching
or physical separation such as in the milling of cereals including rice.
 2. Function of Minerals
 part of the rigid body structure; bone is Ca3(PO4) and Mg.
 part of soft body tissue; K+ controls the pH of intracellular fluids and helps maintain
the osmotic pressure within the cell. Phosphates are concerned with energy release in
cells.
 part of body fluids (fluids outside of cells); Na+ and Cl- are present as ions and
preserve the electrolyte balance in our bodies. If there are large amounts of salt in
our diets, the concentration of it will increase in the blood. To restore the original
concentration, blood is filtered through the kidneys and the ions pass out of the body
through the urine. The pH of blood is 7.4 and this is maintained by a carbonate/
bicarbonate buffer system that involves phosphates and proteins.
 3. FACTORS INFLUENCING BIOAVAILABILITY OF MINERALS
 The bioavailability of a mineral may be influenced by a variety of factors:
 1.The chemical form will determine how readily our bodies absorb the mineral. A
highly stable chelate form would be poorly absorbed compared to free ions that are
readily absorbed. Phytate and oxalate, found in some foods, reduce the absorption of
calcium, iron and zinc. Iodine absorption may be hindered by nitrates.
But, ligands that form soluble chelates with metals will enhance absorption.
In contrast, iron absorption may be increased when vitamin C is consumed during
the same meal.
 2. In high concentrations, some minerals may actually inhibit the absorption of
another mineral. The absorption of iron is inhibited by high concentrations of
calcium, and too much iron itself may lead to poor zinc absorption.
 3. Requirement, The amount of a mineral people actually absorb can vary, and will
depend upon their own needs, and how much they already have of that nutrient in
the body.
 Minerals are fairly stable in normal food processing conditions.
 Calcium
 What is Calcium & Why you need it.
Calcium is the mineral in your body that makes up your bones and keeps them strong.
Ninety-nine percent of the calcium in your body is stored in your bones and teeth. The
remaining 1% is found in the blood and some nerve cells and is essential for nerve
conduction, muscle contraction and blood clotting. As these functions keep you alive minute
to minute, the amount of calcium in the blood must remain at a steady level
 How to get Calcium
There are only two ways you can get this essential 1% of circulating calcium:
 From the calcium in your diet
 From the calcium in your bone
 It is mainly calcium in your diet that spares, or protects, the calcium in your bones.
In addition to their structural role, your bones are your emergency supply of
calcium. Your body actually tears down and builds bone all of the time in order to
make its calcium available for your body’s functions. If you don’t get enough
calcium from the food you eat, your body automatically takes the calcium you need
from your bones. If your body continues to tear down more bone than it replaces
over a period of years to get calcium, your bones become weak and break easily. This
leads to the crippling bone disease called "osteoporosis."
Osteoporosis
 Osteoporosis is a common feature of aging. Loss of bone starts in women at the time
of the menopause and in men at about age 55 and leads to an increase in painful,
disabling fractures 骨折 in both sexes. About 40% percent of women and 13% of
men will suffer a bone fracture due to osteoporosis in their lifetime.
A comparison of normal bone (left) and a bone with osteoporosis (right)
 About 25 million American women have some degree of osteoporosis; the disease
will affect one-third to one-half of post-menopausal women, and 5 million American
men suffer from osteoporosis.
 Peak bone density occurs around the age of 25 and therefore generous calcium
intake in the early 20s is critical. Adequate calcium in the 30s, 40s, and 50s and
beyond is also important in maintaining strong bones.
 Using supplements in addition to calcium-containing foods can help ensure adequate
calcium intake.
What is your Calcium Need?
In 1990, 3/4 of the calcium in our diet came from dairy products. The other quarter was
fairly evenly distributed in all the other foods. Foods that contain small amounts of calcium,
but are not considered good sources, can contribute significant amounts of calcium to an
individual's diet if these foods are eaten often or in large amounts.
Why Calcium
Sources of Calcium
The NICHD recommends milk and other dairy products as a primary source of
calcium. In addition, a variety of other foods are excellent sources of calcium as well. Dark
green, leafy vegetables and foods with added calcium can be healthy ways to get enough
calcium. By eating a wide variety of foods with calcium, you can help make sure to get the
calcium you need each day.
Physical Activity and Bones
In addition to a calcium-rich diet, physical activity is also very important for building
healthy bones. Physical activity is one way you tell your bones that they need to be strong.
Just like exercising your muscles can make them grow bigger, exercising your bones makes
them work harder, which helps them to build up bone mass. And building bone mass as a
child or teenager is especially important because this is when our bones are growing the most.
Studies have even shown that long periods of time with little or no physical activity can
result in a loss of bone mass, putting people at risk for osteoporosis or broken bones.
 Weight-bearing activity, such as walking or running, is one of the best forms of
physical activity for bones because it makes your bones work harder. A
weight-bearing physical activity is one in which your feet and legs carry your weight.
The impact of this weight on your muscles helps build stronger bones.
How much physical activity is enough? In 1996, the U.S. Surgeon General
recommended that everyone age two or older participate in at least 30 minutes of
moderate physical activity on most, preferably all, days. In 2000, the U.S.
Department of Agriculture published its Dietary Guidelines for Americans (DGA),
which also suggests that adults get at least 30 minutes of moderate physical activity
every day. Most small children expend enough energy just from playing and do not
necessarily need additional physical activity.
 But physical fitness is a healthy lifetime habit that should begin in childhood. For
this reason, the DGA also recommends that children over the age of two get 60
minutes of moderate physical activity on most, preferably all, days for the greatest
health benefit.
Weight-bearing activities for children and teens. And make sure you, warm-up
before doing any activity to prevent injury. Be sure that you consult a doctor or
health care professional before starting any physical activity program.
 According to recent USDA surveys, average calcium intakes for women and younger
men are below their RDA. The average calcium intake by women 20 to 29 years of
age was about 778 milligrams per day, and the intake by women 30 to 50 years of
age was about 719 milligrams. Average calcium intake by men 20 to 29 years of age
was 1075 milligrams.
 Do we get enough calcium?
Calcium absorption is dependent upon the needs of the body to calcium, the foods eaten, and
the amount of calcium in the foods eaten.
Vitamin D, whether from diet or exposure to the ultraviolet light of the sun, increases
calcium absorption.
Calcium absorption tends to decrease with increased age for both men and women.
 How Much Do We Need?
How much calcium do we need? The recommended level of calcium for adults age 19
through 50 years is 1000 milligrams per day . An intake of 1200 milligrams of calcium per
day is recommended for those age 51 years and older . In other countries, calcium
recommendations are lower, as low as 600 milligrams daily for adults
 Average Intake of Calcium in the Typical American Diet
The "Other foods" category includes eggs (1.7%), fats and oils (0.1%), sugars and
sweeteners (0.8%), and miscellaneous foods (2.6%).
 How to prepare foods to retain calcium
Calcium is lost in cooking some foods even under the best conditions. To retain calcium:
 Cook foods in a minimal amount of water.
 Cook for the shortest possible time.
Where Do You Fit?
The Dietary Reference Intakes below were released by the National Academy of
Sciences Institute of Medicine in August 1997 -- the Adequate Intake value for different
populations are:
Age Group
Dietary Reference Intakes (DRI)
0 - 6 months
210 mg/day
6 - 12 months
270 mg/day
1 - 3 years
500 mg/day
4 - 8 years
800 mg/day
9 - 18 years
1,300 mg/day
Adults 19 - 50 years
1,000 mg/day
Adults 51+ years *
1,200 mg/day
 What about fortified foods?
Some foods, such as orange juice, bread, and ready-to-eat cereals, are not normally good
sources of calcium but may have had calcium added. Most instant-prepared 速溶的, 方
便的 cereals are fortified with calcium. Since these products vary in the amount of
calcium provided.
 What the research says:
Studies suggest that calcium supplements, if taken regularly, help prevent osteoporosis
by reducing bone loss. The question is how much calcium you need to achieve this.
Although the RDA for calcium is 1,200 mg a day for adults age 51 or older, some experts
believe that some people may need more than that. They recommend calcium in doses of
1,500 mg a day for men over age 65 and postmenopausal women not taking estrogen 雌
激素 replacement therapy.
If you don't get enough calcium in your diet, consider taking a supplement. You may
even experience some side benefits. For example, a 1998 study found that women who
took 1,200 mg a day of chewable calcium carbonate reduced the physical and
psychological symptoms of premenstrual syndrome (PMS) by 20 percent more than
those taking a placebo 安慰剂. In addition, a 14-year study of 86,000 women found that
those who had a relatively high intake of calcium, whether through diet or use of
supplements, had a reduced risk of stroke.
 Cautions
Don't take calcium if you have sarcoidosis 肉状瘤病, — an immune system disorder —
or a high blood-calcium level. See your doctor before taking calcium if you have kidney
disease, chronic constipation, colitis, diarrhea, stomach or intestinal bleeding, irregular
heartbeat or heart problems. If you're pregnant or breast-feeding, don't take calcium in
doses greater than the RDA for pregnant or breast-feeding women. However, if you don't
get enough calcium in your diet, ask your doctor whether calcium supplements are right
for you.
 Side effects
People who take certain forms of calcium supplements may experience constipation and
headache. Serious side effects include confusion, muscle or bone pain, nausea, vomiting
and a slow or irregular heartbeat.
 The Influence of Excessive Protein
Calcium needs appear to be influenced by both protein and sodium intakes. High
protein diets seem to markedly increase the amount of calcium lost from the body every
day . In fact, when young adults had a protein intake of 48 grams per day (slightly lower
than the current RDA) they had no net loss of calcium, even though the amount of
calcium in their diet was as low as 500 milligrams daily .
It has been estimated that for every gram of protein consumed, calcium losses in urine
increase by about 1 milligram . Because we only absorb about 10% of the calcium which
we eat, this means that for every gram of protein, we would need to take in 10 extra
milligrams to make up for urine losses
It is much more likely that protein intakes will be excessive on a meat-based diet or a
diet high in dairy products as shown in Table 2. In addition, it appears that soy protein,
even at high levels, does not increase calcium excretion, the same way that protein from
animal sources does . Diets which are too low in protein (around 44 grams a day) also
appear to have a negative effect on calcium status .Sodium also increases calcium losses
with 5 to 10 milligrams of calcium lost with each gram of salt eaten .
Calcium requirements for those on lower protein, plant based diets may be somewhat
lower than requirements for those eating a higher protein, flesh 肉-based diet. However,
it is important for vegans 严格的素食主义者 to regularly eat foods high in calcium
and/or use a calcium supplement.
 Calcium Supplements
The calcium supplements on the market use a variety of chemical forms of calcium.
Some are more efficiently absorbed than others, and some contain more elemental, or
raw calcium than do others. The table below shows how much actual calcium some
common supplements contain.
Calcium source
% Elemental calcium
Calcium carbonate
40%
Calcium phosphate (tribasic)
39%
Calcium phosphate (dibasic)
30%
Calcium citrate
21%
Calcium lactate
13%
Calcium gluconate
9%
 Note
When purchasing calcium supplements, be aware of the following.
Chewable calcium tablets and calcium powders and solutions may be more easily
absorbed than hard, compressed calcium tablets. Look for "USP" on the supplement's
label to ensure that the tablet will dissolve as it should after being swallowed.
Be aware that calcium supplements made from bone meal or dolomite 白云石 may
contain toxic substances such as lead, mercury and arsenic. It's unclear if the levels are a
cause for concern, though, as a variety of natural foods also contain these substances.
Your body's ability to absorb calcium from supplements is best at 500 mg elemental
(available) calcium or less per dose. Taking doses of more than 500 mg won't harm you,
but doing so won't necessarily provide you any extra benefit. The label usually tells you
how much of the calcium is elemental. If you take an iron supplement, don't take it at
the same time as your calcium supplement. Calcium can interfere with the absorption of
iron. For best results, take calcium carbonate supplements with a meal.
 1. Introduction
Iron is the vital element in life. The major scientific and medical interest in iron is as an
essential metal. But the toxicological considerations are important in term of the
accidental acute exposure and chronic iron overload. The disposition of iron in human
body is regulated by a complex mechanism to maintain homeostasis.
Iron concentration in body tissue must be tightly regulated because excessive iron leads
to tissue damage, as a result of formation of free radical. It has capacity to accept and
donate electrons readily. The content of body iron is regulated primarily by absorption
since humans have no physiological mechanism by which excessive iron is excreted .
2. History background of the research
 In the 18 century, man had researches on the nutritional function of iron,and proved
it to be the blood’s main ingredient.
 In 1892, Bunge described baby are prone to 倾于...lacking iron. In 1928, Mackay
proved the lacking of iron is the main cause of prevalent in anemia in western
London.
 In 1932, Castle and his colleagues verified iron can be used to compose haemoglobin.
Iron is the 26th element in periodic table. The molecular weigh is 55.85, which is the
fourth most common element except oxygen, aluminium, Silicon in solid state, it has two
forms: metal and compound; in dissolve state, it is in form of oxide: bivalent and
trivalent ion. Iron transform between the two forms, which is one of characteristics and
make catalysis in redox reaction by accepting and donating electrons.
 3. DISTRIBUTION
Iron account for about 0.1 percent of the mineral elements in the body and the total
amount of the iron in the body of a healthy adult is only about 4g. From the study of Ray
Yip (2001) the total amount of iron in body are 3.8g for men and 2.3g for women, 2/3 of
which is functional .
DISTRIBUTION
 Over half of this is found in the red blood cells in the pigment haemoglobin which
transports oxygen from the lungs to the tissues.]
 A small proportion of the iron in the body is present in the muscle protein myoglobin
肌 球 素 ; some cell enzymes, such as the cytochromes, also contain iron. The
remainder of the iron in the body is stored in the liver, spleen and bone marrow in
the form of
specialized iron-binding proteins called ferritin 铁 蛋 白 and
hemosiderin 血黄铁质.
Function
Here we refer to the physiological function. because the form of iron in body is as
compounds, we discuss it according to different compounds
 In the form of haemoglobin it is critical to transport oxygen from lung to tissue and
carbon dioxide from tissues to lungs. Hemoglobin also has a mild buffering function
in maintaining the pH of the blood.
 In the form of myglobin its basic function is to transport and storage oxygen in
muscle.
 Cell pigment: it is a serial of compound containing heme (亚铁血红素).
 An important part of enzymes needed in the oxidation reactions to release energy in
the cells.
Iron Metabolism
 Once iron is taken with food , it will go though a serial changes:
absorption
transport
storage
renewal and loss
Normal Iron Metabolism
 A well-balanced diet contains sufficient iron to meet body requirements. About 10%
of the normal 10 to 20 mg of dietary iron is absorbed each day, and this is sufficient
to balance the 1 to 2 mg daily losses from desquamation 脱落 of epithelia.
 Greater iron utilization via growth in childhood, greater iron loss with minor
hemorrhages 出血, menstruation 月经 in women, and greater need for iron in
pregnancy will increase the efficiency of dietary iron absorption to 20%.
Absorption
 Iron is mainly absorbed in the duodenum and upper jejunum. A transporter protein
called divalent metal transporter 1 (DMT1) facilitates transfer of iron across the
intestinal epithelial cells. DMT1 also facilitates uptake of other trace metals, both
essential (manganese, copper, cobalt, zinc) and toxicity (cadmium, lead). Absorbed
iron is bound in the bloodstream by the glycoprotein named transferrin 铁传递蛋白.
Normally, about 20 to 45% of transferrin binding sites are filled (the percent
saturation) with iron.
 About 0.1% of total body iron is circulating in bound form to transferrin. Most
absorbed iron is utilized in bone marrow for erythropoiesis 红血球生成. Membrane
receptors on erythroid precursors in the bone marrow avidly bind transferrin. The
trace elements cobalt and manganese are also absorbed and transported via the
same mechanisms as iron.
Iron absorption is regulated by three mechanisms:
 Dietary regulator: a short-term increase in dietary iron is not absorbed as the
mucosal cells have accumulated iron and "block" additional uptake.
 Stores regulator: as body iron stores fall, the mucosa is signalled to moderately
increase absorption.
 Erythropoietic 红血球生成的 regulator: in response to anemia the erythroid cells will
signal the mucosa to increase iron absorption more significantly.
Storage
 Iron is initially stored as ferritin, but ferritin can be incorporated by
phagolysosomes 吞噬溶酶体 to hemosiderin 血黄铁质. There are about 2 gm of iron
in the adult female, and up to 6 gm iron in the adult male. About 1.5 to 2 gm of this
total is found in red blood cells as heme in hemoglobin, and 0.5 to 1 gm occur as
storage iron, with the remainder in myoglobin and in enzymes that require iron.
Storage iron occurs in two forms:
 Ferritin 铁蛋白
 Hemosiderin
About 10 to 20% of absorbed iron goes into
a storage pool, which is also being recycled
into erythropoiesis, so there is a balance of
storage and use.
What affects iron absorption?
 Iron absorption refers to the amount of dietary iron that your body obtains from
food. Healthy adults absorb about 15% of the iron in their diet, but your actual
absorption is influenced by your body’s iron stores, the type of iron in the diet, and
by other dietary factors that either help or hinder iron absorption.
What affects iron absorption?
 The greatest influence on iron absorption is the amount stored in your body. Iron
absorption significantly increases when body stores are low. When iron stores are
high, absorption decreases to help protect against iron overload .
What affects iron absorption?
 Absorption of heme iron is very efficient and not significantly affected by the
composition of your diet. Only 1% to 7% of the nonheme iron in vegetable staples
such as rice, maize, black beans, soybeans and wheat is absorbed when consumed as
a single food . However, dietary factors can significantly improve nonheme iron
absorption. Meat proteins and vitamin C will improve the absorption of nonheme
iron .
What affects iron absorption?
 Diets that include a minimum of 5 servings of fruits and vegetables daily, as
recommended by the Food Guide Pyramid, should provide plenty of vitamin C to
boost nonheme iron absorption.
 Calcium, polyphenols and tannins found in tea, and phytates, which are a
component of plant foods such as legumes, rice and grains, can decrease the
absorption of nonheme iron (1,11-15). Some proteins found in soybeans also inhibit
nonheme iron absorption (1,16). Most healthy individuals can maintain normal iron
stores when the diet provides a wide variety of foods as suggested by the Food Guide
Pyramid.
What affects iron absorption?
 It is most important to include foods that enhance nonheme iron absorption when
total daily iron intake does not meet the RDA, when iron losses are exceptionally
high, or when no heme iron is usually consumed.
Deficiency and overload
When can iron deficiency occur? The World Health Organization considers iron
deficiency the number one nutritional disorder in the world. It affects more than 30% of
the world’s population. When your need for iron increases or a loss of iron from
bleeding exceeds your dietary iron intake, a negative iron balance may occur. Initially
this results in iron depletion, in which the storage form of iron is decreased while blood
hemoglobin level remains normal. Iron deficiency occurs when blood and storage levels
of iron are low, and the blood hemoglobin level falls below normal.
 Iron deficiency anemia may result from a low dietary intake, inadequate intestinal
absorption, excessive blood loss, and/or increased needs . Women of childbearing age,
pregnant women, older infants and toddlers, and teenage girls are at greatest risk of
developing iron deficiency anemia because they have the greatest needs
 Individuals with renal failure 肾衰竭, especially those receiving dialysis, are at high
risk for developing iron deficiency anemia. This is because their kidneys cannot
create enough erythropoietin (促)红细胞生成素, a hormone needed to make red
blood cells. Iron and erythropoietin can also be lost with blood during dialysis,
which can result in an iron deficiency. Extra iron and erythropoietin are usually
needed to help prevent iron deficiency in these individuals.
 Iron deficiency could also be caused by low vitamin A status. Vitamin A helps to
mobilize iron from its storage sites, so a deficiency of vitamin A limits the body’s
ability to use stored iron. This results in an “apparent” iron deficiency because
hemoglobin levels are low, even though the body can maintain normal amounts of
stored iron (27,28). While uncommon in the U.S., this problem is seen in developing
countries where vitamin A deficiency often occurs.
 Signs of iron deficiency anemia include feeling tired and weak, decreased work and
school performance, slow cognitive and social development during childhood,
difficulty maintaining body temperature, and decreased immune function, which
may decrease resistance to infection. During pregnancy, iron deficiency is associated
with increased risk of premature deliveries 早产, giving birth to infants with low
birth weight, and maternal complication 母性的并发症.
Overload
 Iron Poisoning:
Acute iron poisoning is mainly seen in children. A single 300 mg tablet of ferrous
sulfate will contain 60 mg of elemental iron. Toxicity producing gastrointestinal
symptoms, including vomiting and diarrhea, occurs with ingestion of 20 mg of elemental
iron per kg of body weight. If enough iron is ingested and absorbed, about 60 mg per kg
body weight, systemic toxicity occurs. Toxicity results when free iron not bound to
transferrin appears in the blood. This free iron can damage blood vessels and produce
vasodilation 血管舒张 with increased vascular permeability, leading to hypotension and
metabolic acidosis.
Overload
In addition, excessive iron damages mitochondria and causes lipid peroxidation,
manifest mainly as renal and hepatic damage.
 Early signs of iron poisoning include vomiting and diarrhea, fever, hyperglycemia,
and leukocytosis 白细胞增多. Later signs include hypotension, metabolic acidosis,
lethargy 无生气, seizures, and coma 昏迷. Hyperbilirubinemia and elevated liver
enzymes suggest liver injury, while proteinuria 蛋白尿 and appearance of tubular
cells in urine suggest renal injury.
 Chronic Iron Overload: This can occur in patients who receive multiple transfusions
输液 for anemias caused by anything other than blood loss. Patients with congenital
先天的 anemias may require numerous transfusions for many years. Each unit of
blood has 250 mg of iron.
 Ineffective Erythropoiesis: Increased iron absorption can occur in certain types of
anemia in which there is destruction of erythroid cells within the marrow, not
peripheral destruction. This phenomenon signals the erythroid regulator to
continually call for more iron absorption. These conditions include: thalassemias,
congenital dyserythropoietic anemias, and sideroblastic 铁粒幼红细胞 anemias.
Dietary Resource of Iron
 The main dietary sources of iron are meat, bread, and other cereal products,
potatoes and vegetables. In some areas water may take a small contribution.
However,even the richest dietary sources of iron contain only very small amounts of
the element. Lamb’s liver, the richest resources, contains only about one part of iron
in 10000.
Dietary Resource of Iron
 Bread and other cereal-based foods: about 40 percent of the total iron intake
 Meat and vegetables each provide about 20 percent
 eggs about five percent .
 Iron is one of the mineral elements which may be lacking in an average diet and
for this reason it is added to all flour in Britain, except whole meal flour, so that its
iron content is at less 1.65mg/100g. Unfortunately , however , studies have shown
that most of the iron added to flour passes through the body unabsorbed
Food
Iron content
(mg/100g)
Food
Liver,lambs,
10.9
Eggs,boiled
Kidney,pigs
9.1
Bread,white
1.7
Flour,wholemeal
4.0
Baked beans
1.4
Spinach,boiled
4.0
Cod ,fried
0.5
Oats,porridge
3.8
Cabbage,boiled
0.4
Beef,cooked
3.0
Potatoes,boiled
0.4
Sardines,canned
2.9
Cheese,cheddar
0.4
or
2.5
apples
0.3
Flour,72%extract-ion
2.2
milk
0.1
Bread,brown
wholemeal
Iron content
(mg/100g)
2.0
What is the Recommended Dietary Allowance for Iron

The Recommended Dietary Allowance (RDA) is the daily dietary intake level that is
sufficient to meet the nutrient requirements of nearly all (97-98%) healthy individuals in
each life-stage and gender group .
Age
Infants,
Males Females
Pregnancy
Lactation
Children
7 to 12 months
11 mg
1 to 3 years
7 mg
4 to 8years
10 mg
9 to 13 years
8 mg
8 mg
14-18 years
11 mg
15 mg
27 mg
10 mg
19-50years
8 mg
18 mg
27 mg
9 mg
51+ years
8 mg
8 mg
Zinc
Distribution In The Body
 muscle tissue
 bones
 eyes
 prostate gland
 testes 睾丸
 skin and kidneys
More than half of the body's zinc supply is found in muscle tissue. This mineral is also
found in other parts of the body, which include the bones, eyes, prostate gland, testes,
skin and kidneys.
Physiological Functions
 Cofactor
 Bolsters Immunity
 Boosts Brain Activity of Children
 Heals and Protects Skin
 Stimulates Taste, Smell and Mood
Zinc has numerous functions in the body.
 (1) This mineral serves as a cofactor for over 100
enzymes in the body, especially those involved
with the metabolism of protein, carbohydrate,
fat and alcohol. Transport of vitamin A
 (2) Bolsters Immunity
Zinc helps regulate the production of cells in the body's immune system, which protect
against infection and some cancers. Zinc acts as a critical ingredient to immune cell
function, assisting in cell division and growth. And as a component in thymic 胸腺的
hormone, zinc serves to control the maturation of Lymphocytes. In many elderly
individuals, immunity decreases, making them more susceptible to disease. Providing
adequate zinc-and a balanced diet- has been shown to help decrease their rate of
infectious diseases. There is also evidence that zinc deficiency is implicated in
deteriorating vision that comes with aging.
 (3) Boosts Brain Activity of Children
Zinc also is imperative for proper learning, and task and behavioral performance in
children. Found in vesicles 囊 of the mossy 生 苔 的 fiber system of the brain's
hippocampus, zinc interacts with other chemicals to send messages to the sensory brain
center, enhancing memory and thinking skills. Research has shown that zinc deprivation
causes poor growth and maturation of the cerebellum 小脑 and impairs the development
of brain cells, which may contribute to learning disorders or emotional and behavior
problems. Other studies have shown that zinc deprivation has a significant effect on
cognitive function, resulting in learning impairments and deficits in working visual
memory.
 Heals and Protects Skin
Zinc is essential for healthy skin. As a drying agent and astringent 收敛性的, zinc oxide
has been used for generations to soothe diaper rash 尿疹 and relieve itching 痒的. And
zinc is a natural sun screen, protecting chapped lips and skin from the sun's harmful
rays. Zinc sulfate is effective in treating some cases of acne 粉刺." And in a water-based
solution, zinc sulfate helps remedy cold sore 唇疱疹. Zinc also improves healing of
wounds, like surgical incisions, burns and other skin irritations. Used as an
anti-inflammatory, zinc soothes 缓和或减轻 skin and skin tissue. Poison ivy 毒葛,
sunburn, blisters and gum disease are all improved when treated with zinc. It is even a
natural insect repellent 杀虫剂 And zinc stimulates the transport of Vitamin A from the
liver to the skin, helping to protect body tissue from damage.
 (5) Stimulates Taste, Smell and Mood
Zinc activates areas of the brain that receive and process information from taste and
smell sensors. Its importance to appetite was first demonstrated in 1972 when
researchers showed taste disorders responded to zinc supplementation. Levels of zinc in
plasma and zinc's effect on other nutrients, like copper and manganese, were found to
influence appetite and taste preference.
Factors Affecting Availability
(1) Since minerals may compete for absorption sites in the intestine, excess intakes of iron or
copper can adversely interfere with zinc absorption.
(2) Phytate, fiber found in grains and other fiber-rich foods, binds zinc and reduces
absorption, as can alcohol.
(3) The body absorbs 15-40% of dietary zinc, depending on the body's requirement for this
mineral
(4) Calcium, phosphorus, vitamin A, C. Vitamin D increases absorption.
Food Sources
The best sources of zinc are lean red meats and seafoods - especially oysters. Other
sources include cereals and rice, beans, cheese, and nuts - including peanut butter.
Although phytates and fiber found in unprocessed grains inhibit the bioavailability of
zinc, whole grains are still a better source of zinc than that found in refined grains (e.g.
white bread). Whole grain yeast breads enhance the absorption of zinc by producing
enzymes that destroy phytates. Zinc from meat products, on the other hand, is four times
more bioavailable than that found in fibrous grain foods. The body best absorbs smaller
amounts of zinc at one time.
Deficiencies
Many of the features of common chronic disorders, especially connective 结缔 tissue
disorders, are identical to the symptoms of zinc deficiencies.
Deficiencies
 Decreased appetite
 Growth failure in children
 Delayed development of sex organs
 Reduced immune function
 Poor wound healing
Excess
Too much zinc can cause gastrointestinal irritation (upset stomach), interfere with copper
absorption and cause copper deficiency, and (like too little zinc) cause immune deficiency.
According to the National Academy of Sciences, the Recommended Dietary Allowances of
zinc are 12 milligrams per day for women and 10 milligrams per day for men.
Magnesium
Function of Magnesium
 Magnesium is necessary for the proper function of over 300 enzymes essential for
actions such as the transmission of nerve impulses, muscle contraction and the heart
beat.
 Magnesium is required for protein synthesis and for releasing energy from the
body's carbohydrate stores in the liver.
 Magnesium also helps in bone building and in the release of energy from food.
 A limited amount of scientific research suggests that normal amounts of magnesium
may...
 Protect you from heart disease.
 Help lower high blood pressure.
 Help relieve migraines. 偏头痛
 Strengthen exercising muscles and increase endurance.
 Help prevent recurrent kidney stones.
 Work with calcium to protect against postmenopausal bone loss.
 Claims have been made that magnesium can alleviate
 insomnia,
 anxiety,
 depression,
 irritability,
 muscle tremors, 震动, 颤动
 weakness,
 fatigue,
 poor memory,
 water retention
 premenstrual 经期前的 syndrome.
However, scientific support for these claims is lacking at the present time.
If I don't get enough/Deficiency?
 Magnesium deficiency can lead to loss of appetite, confusion, diarrhea, nausea,
vomiting, tremors and even uncontrolled muscle contractions.
 Even a marginal deficiency can contribute to cardiac rhythm abnormalities.
Although magnesium deficiency is rare, some population groups may be at high risk
for developing magnesium deficiencies.
Deficient Groups include:
 Those who take diuretics 利尿剂
 Those undergoing cancer chemotherapy
 Those taking digitalis drugs 洋地黄
 Those taking antibiotics
 Heavy drinkers
 Those who have had a heart attack
 Those who have kidney problems
 Diabetics
But if you have kidney or heart problems, do not take Mg supplements without
consulting a qualified physician. In addition, large doses of Mg have potentially toxic
and even lethal effects.
Magnesium Sources
 Magnesium is widely available in fruits, leafy vegetables, grain products, Legumes,
chocolate, mineral water and shellfish.
 Normally healthy people can easily get adequate magnesium from ordinary foods
Recommended Intakes --RDAs:
 350 mg/day for adult males over age 18
 280 mg for females over age 18
 20 mg for adult females - pregnant
 355 mg for females lactating 0-6 months
 340 mg for females lactating 6 months+
 400 mg for males ages 15-18
 300 mg for females ages 15-18
 270 mg for males ages 11-14
 280 mg for females ages 11-14
 170 mg for children ages 7-10
 120 mg for children ages 4-6
 80 mg for children ages 1-3
 60 mg for infants ages 0.5-1.0
 40 mg for infants ages 0-0.5
Manganese
 Manganese is an essential trace mineral in animal nutrition and is believed to be an
essential trace mineral in human nutrition
Manganese Deficiency
 Dietary manganese-deficiency in animals results in a wide variety of structural and
physiological defects, including growth retardation, skeletal and cartilage
malformations, impaired reproductive function, congenital ataxia 共济失调 due to
abnormal inner ear development, optic nerve abnormalities, impaired insulin
metabolism and abnormal glucose tolerance, alterations in lipoprotein metabolism
and an impaired oxidant defense system.
 Manganese deficiency states have not been well documented in humans. There is one
report of a man maintained for four months on a manganese-deficient diet and also
given magnesium-containing antacids. The symptoms which occurred included a
decrease in serum cholesterol, depressed growth of hair and nails, scaly 有鳞的
dermatitis 皮炎, weight loss, reddening of his black hair and beard and impaired
blood clotting. In another report, men fed a low-manganese diet manifested low
serum cholesterol levels and dermatitis. Short-term manganese supplementation did
not reverse these symptoms.
 In still another report, young women fed a manganese-poor diet were found to have
mildly abnormal glucose tolerance and increased menstrual losses of manganese,
calcium, iron and total hemoglobin.
 Finally a child on long-term total parenteral nutrition (TPN) lacking manganese
manifested bone demineralization and impaired growth that were corrected by
supplementation with manganese.
Function
 Manganese is the preferred metal cofactor for glycosyltransferases.
Glycosyltransferases are important in the synthesis of glycoproteins and
glycosaminoglycans 粘 多 糖 (GAGs or mucopolysaccharides). Glycoproteins are
involved in the synthesis of myelin and the clotting factors, among other things.
Manganese-containing metalloenzymes include manganese superoxide dismutase,
the principal antioxidant enzyme of mitochondria, arginase, pyruvate 丙酮酸盐
carboxylase and glutamine synthetase.
Antioxidant activity of Mn
 Manganese may have antioxidant activity. Manganese has putative anti-osteoporotic
and anti-arthritic activities.
 MECHANISM OF ACTION
 Manganese ions have been found to scavenge hydroxyl and superoxide radicals. The
mechanism of binding of manganese ions to these reactive oxygen species is not
known. Manganese is a crucial component of the metalloenzyme manganese
superoxide dismutase (MnSOD). MnSOD is found in mitochondria and is the
principal constituent of the mitochondrial oxidant defense system. Rats and mice fed
manganese-deficient diets are found to have reduced MnSOD activity in heart
muscle and nervous tissue. They also have mitochondrial abnormalities and
pathological changes in these tissues. The pathological changes are thought to result
from oxidative damage due to the decreased activity of MnSOD which normally
would protect against this damage.
 Dietary manganese deficiency results in skeletal and cartilage malformations in
animals and in one human report. It is thought that this is due to decreased activity
of the manganese-dependent glycosyltransferases which, among other things, are
involved in the synthesis of glycosaminoglycans or GAGs. GAGs are crucial for
healthy cartilage and bone. However, there is as yet only very preliminary evidence
that supplemental manganese has any effect on the promotion of bone or cartilage
formation in humans who are not manganese-deficient. One study reported that
manganese when taken in combination with calcium, copper and zinc may improve
bone mineral density in postmenopausal women with osteoporosis.
Sources
 The richest dietary sources of manganese include whole grains, nuts, leafy vegetables
and teas. Manganese is concentrated in the bran of grains which is removed during
processing.
 Mean intakes of manganese worldwide range from 0.52 to 10.8 milligrams daily.
ADVERSE REACTIONS
Oral manganese supplements are generally well tolerated. Oral manganese, however,
may be neurotoxic in those with liver failure. Manganese is primarily eliminated via the
biliary route, and hepatic dysfunction leads to depressed manganese excretion.
Manganese may accumulate in the basal ganglia 神经中枢 of those with liver failure and
may exacerbate 恶化 hepatic encephalopathy and/or cause Parkinson‘s disease-like
symptoms.
 Manganese is toxic under certain conditions. Hepatic failure was discussed above.
Mine workers exposed to high concentrations of manganese dust develop what is
known in the mining villages of northern Chile, where this disorder has been found,
as "locura manganica" or manganese madness. In later stages of this disease,
symptoms similar to those of Parkinson's disease are observed. Levodopa is the
treatment of the later stages of manganese madness.
 There are a few reports of manganese intoxication occurring in those on long-term
total parenteral nutrition (TPN) who developed parkinsonism which was treated
with levodopa.
 Recommendation
 The Food and Nutrition Board of the U.S. National Academy of Sciences has
recommended the following estimated safe and adequate daily dietary intake
(ESADDI) values for manganese:
 Age (years)
ESADDI (milligrams)
 0 to 0.5
0.3 to 0.6
 0.5 to 1
0.6 to 1.0
 1 to 3
1.0 to 1.5
 4 to 6
 7 to 10
 11 to 18
 Adults
Selenium
1.5 to 2.0
2.0 to 3.0
2.0 to 5.0
2.0 to 5.0
Function
 Selenium is required for the activation of an enzyme called glutathione peroxidase.
This enzyme is an antioxidant that quenches hydroperoxides, "high energy“ oxygen
- containing molecules that are produced during the metabolism of fat and that are
highly toxic to cells. Recent research showed that selenium could reduce the severity
of some cancers. This is thought to be due to selenium inducing ”apoptosis (自溶)"
(programmed cell death) in cancer cells.
 Selenium is also involved in a healthy immune system and proper thyroid function.
What to look for in a selenium supplement
 Selenomethionine is the principal form of selenium found in foods. Selenomethionine
is virtually 100% absorbed and well retained as compared to inorganic selenium,
which is rapidly excreted.
 Yeast preparations can be produced to contain substantial amounts of
selenomethionine suitable for selenium supplements.
 Some manufacturers mechanically mix sodium selenite or selenium dioxide, with
ordinary yeasts. These yeast products contain virtually no selenomethionine. The
selenium in these yeasts is significantly less bioavailable than selenomethionine.
Studies have shown that such yeast products produce only small increases in blood
selenium concentrations.
 Other artificially selenized yeasts contain sodium selenate, which is not normally
present in foods. A study found that selenate was less effective than selenomethionine
to correct a deficiency.
 Recommended Intakes
RDAs:
70 µg/day for adult males
55 µg for adult females
65 µg for adult females - pregnant
75 µg for adult females - lactation
40 µg for males ages 11 - 14
50 µg for children ages 15 - 18
45 µg for females ages 11 - 14
40 µg for males ages 11 - 14
30 µg for children ages 7 - 10
20 µg for children ages 1- 6
15 µg for infants 6 mo - 1 yr
10 µg for infants 0-6 months
 Food Sources
Seafoods, meats, grains, Brazil nuts
Main Minerals
Mine
ral
Main Function
Main Sources
Deficiency
Excess
Calci
um
Formation and
maintenance of
bones and teeth.
Blood
clotting
and
nerve
function.
Milk,
cheese,
yogurt and canned
fish
are
rich
sources. Also dark
green
leafy
vegetables, white
and brown flour
and bread.
Bone
weakeningrickets and
osteomalaci
a. This is
also due to
failure to
absorb
calcium
owing
to
vitamin D
deficiency.
Not known in adults
Sodiu
m
Regulation
of
body
water
content.
Nerve
function.
Salt - either added
to foods during
processing or at
home in cooking or
at the table.
Fatigue,
nausea,
cramps.
Thirst
is
experience
d.
Excess sodium has been
linked to hypertension.
Potas
sium
Functioning
of
cells. Constituent
of body fluids.
All foods except
sugars, fats and
oils. Unprocessed
foods have more
potassium
than
processed foods.
Weakness,
mental
confusion
and,
if
extreme,
heart
failure.
Excess
is
dangerous
especially if the kidneys are
not functioning properly.
Magn
esium
Involved
in
energy transfer
in the cell, in
enzyme activity
and
muscle
functioning.
Widespread
but
wholegrain cereals,
nuts and spinach
are good sources.
Depression,
irritability,
fits,
tiredness
and,
if
extreme,
heart
attack.
Excess magnesium is not
absorbed.
Phos
phor
us
An
essential
component of all
cells and present
in bones and
teeth.
Milk, cheese, meat,
fish and eggs are
good sources.
Dietary
deficiency
unknown.
Not known in adults.
Table 2 Trace Minerals
Mineral
Main Function
Main Sources
Deficiency
Excess
Iron
Formation
of Red meat and offal are Iron deficiency Excessive absorption may be
haemoglobin in red rich sources. Cereals, anaemia.
due to a rare genetic disorder.
blood cells.
bread, and vegetables
contain some.Breakfast
cereals may be fortified.
Zinc
Essential
for Milk, cheese, meat, eggs Dietary
Interferes
growth, and sexual and fish, wholegrain deficiency
is metabolism.
maturation.
cereals and pulses.
rare; may cause
Involved in enzyme
delayed puberty
activity and taste
and
retarded
perception.
growth.
Iodine
Formation
of Milk, seafood, seaweed. Goitre 甲 状 腺 Excess iodine is not absorbed.
thyroid hormones. Iodised foods such as 肿 and
salt.
cretinism. 呆 小
症
with
copper
Fluoride Increases
the Fluoridated water, tea, Tooth
decay Fluorosis.
resistance of teeth to fish and toothpaste.
more likely.
decay.
Selenium As an antioxidant it Cereals, meat, fish, Keshan disease Excess selenium is toxic.
protects
cell offal, cheese and eggs. (a type of heart
membranes against
disease).
oxidation.
Food Nutrition
Deng Zeyuan Part 9
1. Cereals
•
wheat is the cereal most commonly used for the manufacture of food products, although
many other types of cereals are used. Each cereal has unique properties which make it
suitable for a variety of food products. Cereals require different conditions to grow. For
example, rice is grown in damp tropical climates, eg India and China, and oats in cold
temperate climates, eg Scotland. Cereals are also known as ‘staple foods’ as they often
make up the bulk of the diet since they are relatively cheap to produce.
1. TYPES
•
1). Wheat is usually ground to flour which is used to produce a wide range of products.
The type of flour produced differs according to the rate of extraction. Cous cous is also
made from wheat.
2). Rice
•
Brown rice has its outer husk removed, and white rice is milled and polished further to
remove the bran and germ. There are many different types of rice, categorised by size,
shape and the region where they are grown. Rice can be ground to make flour.
3). Maize
Maize may be processed to make many different ingredients and food products. It may be milled
in a similar process to wheat. Its germ is rich in oil, which is refined to produce corn oil.
4). Oats
•
Oats are rolled rather than crushed during processing. Coarse, medium and fine grades of
oatmeal are available.
5). Barley and Rye
•
Barley is mainly sold as pearl barley, which is the whole grain with its husk removed
• Rye 裸麦 contains little gluten, so produces breads with low volume and a dense texture
2. CHARACTERISTICS
•
1). Protein: The amount of protein in each cereal differs, and this affects the final product.
Bread, with its characteristic open texture and appearance, relies on high protein flour, eg
wheat flour. In products such as cakes, biscuits and pastry, low protein cereals are used to
produce crumbly and light textures.
2). Gelatinisation
•
Gelatinisation (thickening): When a flour (wheat, corn, rye or rice) is added to a liquid,
the starch granules begin to swell on heating. This causes the granules to rupture and
starch is released into the liquid. The starch granules absorb liquid, causing the sauce to
thicken. Rice flour can be used in acidic sauces as it is resistant to the effects of low pH.
Pearl barley may also be used to thicken a soup or casserole. However, small lumps of
barley will remain.
3) Rice:
•
Rice: Rice grain is eaten whole and is used less frequently for manufacturing other
products than wheat and maize. It is sometimes used to ‘bulk’ a food product, eg
vegetarian burger, or used as a side or main dish, eg risotto, philaf.
4) Products:
•
Products: Cereals are used in a variety of breakfast cereals, They are processed by
different methods to produce a range of products. Some nutrients are lost during this
processing but are added at a later stage known as ‘fortification’.
Nutrition
a. Composition of Cereal protein (%)
Cereals
Albmin (白蛋 Globulin（球蛋 Prolamin （ 醇 Glutelin （谷
白)
白）
溶蛋白）
蛋白）
Rice
5
10
5
80
wheat
3-5
6-10
40-50
30-40
corn
4
2
50-55
30-45
sorghum
1-8
1-8
50-60
32
BV%: Rice 77, wheat 67, barley 64, corn 60, sorghum 56
•
•
•
B. Other:
CHO >70%. Best Source of Energy.
Fat: 1-2%, corn: 1-4%.
UNSFA 80%, Linoleic Acid: 60%
• Minerals: 1.5-3%. Rich : P and Ca, Fe 1.5-3 mg/100g
• Vit: Rich VB: B1,B2, B5, B6
3. STORAGE
Cereals should be kept in a cool dry place. They are prone to infestation by insects if kept for long
periods of time.
3. Legume
• Protein: 35-40% Ideal complementary protein for botanical foods
• Fat: 15-20%, UNSFA 85%, linoleic acid 50%, PLP (磷脂) 1.64%。
• Rich; Ca, B1 and B2
• CHO: 25-30%,
AA content (g)in 100g protein
EAA
WHO ratio
Egg
soybean
Mung bean
Isoleucine
4.0
4.8
5.2
4.5
Leucine
7.0
8.1
8.1
8.1
Lysine
5.5
6.5
6.4
7.5
Methionine
3.5
4.7
2.5
2.3
Phenylalanine 6.0
8.6
8.6
9.7
Threonine
4.0
4.5
4.0
3.6
Tryptophan
1.0
1.7
1.3
1.1
Valine
5.0
5.4
4.9
5.5
Nutrients contents in 100g
Protein(g) Fat
(g)
CHO
(g)
VA(ug)
B1 (mg) B2 (mg)
15
0.02
0.02
0.04
0.03
Joice
of 1.8
soybean
0.7
1.1
Toufu
3.7
4.2
Fruits
8.1
Fruit and Vegetables
Fruit and vegetables have adapted to local climatic and geographic conditions all over the
world, resulting in many different varieties. With modern distribution systems it is new easy
to obtain fruit and vegetables all year round, and from many different countries.
COMPOSITION
Although fruits and vegetables may look different, the edible part is made up from similar
types of cells. The cell has an outer wall which is made up mostly from cellulose. Within the
cell there is a jelly-like substance called cytoplasm, which carries fat droplets and colour
pigments. In potatoes and yams starch is also carried in this substance.
•
The major part of the cell, called the vacuole, contains cell sap. The sap is watery
and contains sugar, pigments and salts. Between the cells are small pockets known as
intercellular air spaces, which give raw fruits and vegetables their opaqueness.
CHARACTERISTICS
•
Processing: Whether fruit and vegetables are to be canned, frozen, pickled or eaten
raw, further processing is required, eg cleaning and trimming, peeling, chopping and
washing. The processing of fruits and vegetables may alter their physical
characteristics and lead to losses of nutrients. Vitamin C is the most commonly
affected nutrient. Cut or shredded fruit or vegetables have a shorter shelf-life than
those which have not been processed.
Spoilage: The acidic nature of fruits and vegetables acts as natural protection against
spoilage by micro-organisms. Fruit and vegetables continue to live after they are picked, ie
they absorb oxygen, give off carbon dioxide and tend to become warmer. Fruits have a
higher sugar content than vegetables, which makes some varieties susceptible to mould
growth. Fruits ripen and vegetables mature on storage. Changes in flavour, appearance and
loss of texture occur.
• Colour: Fruits and vegetables contain natural colour pigments which may be used to
colour foods. However, the stability of the pigments is affected by pH, light and heat.
Freshly cut fruit, such as bananas, apples and peaches will discolour quickly in open
air. This oxidation is called enzymic browning. This may be slowed down by the use
of antioxidants or prevented by adding an acidic or sugary solution to the surface of
the fruit or keeping it at cold temperatures. A similar reaction also occurs in some
vegetables, such as potatoes.
•
Cooking: During cooking the cell structure starts to break down. This is why raw
fruits and vegetables become softer when cooked. Some nutrients are also lost. This
is due to the loss of water and other solubles in the sap.

·Products: Many varieties of fruits and vegetables are preserved by canning,
dehydration or freezing. The preservation process may alter physical, nutritional
and sensory characteristics.
•
Jellying: Some fruits, such as apples and blackcurrants, contain rich sources of
pectin. Pectin is used to set jam.

·Nutrition: It is recommended that we eat five portions of fruit and vegetables daily.
This group of foods includes rich sources of a number of nutrients, eg vitamin C,
folate, dietary fibre, beta-carotene and potassium.
Fruit types
• Soft fruits, eg raspberry, blackberry, redcurrant, strawberry, bilberry.
• Citrus fruits, eg orange, lime, lemon, kumquat, grapefruit.
• Stone fruits, plum, apricot, peach, lychee, cherry, mango.
• Fleshy fruits, eg apple, papaya, pineapple, pear, banana
• Vine fruits, eg grape, water melon, cantaloupe
• Vegetable types
• Fruit vegetables, eg aubergine 茄子, marrow, plantain, tomato
• Pulses, eg pea, bean, lentil
• Flower vegetables, eg broccoli, cauliflower, calabrese
• Leafy vegetables, eg spinach, cabbage, parsley, endive, lettuce, watercress
• Stem vegetables, eg asparagus, fennel, celery
• Fungi, eg oyster and button mushroom
• Tubers, eg potato, sweetpotato, yam, cassava, jerusalem artichoke
• Bulbs, eg onion, garlic, shallot, leek
• Roots, eg beetroot, swede, salsify, carrot, parsnip, radish
Vitamin content (/100g)
Hot
Brocoli Spinach Carrot jujube orange peach
pepper
grape
Vc (mg)
72
61
32
16
243
19
7
25
Carrotin
(ug)
340
30
487
4010
240
520
20
50
B2 (mg)
0.03
0.08
0.11
0.04
0.09
0.03
0.03
0.02
STORAGE
Fresh fruit and vegetables should be used as soon as possible. If stored, they should be kept
in a cool, dark place to prevent sprouting, mould growth and rotting
3. Fats and Oils
Error!
Fats and oils have the same chemical structure. Fats which are liquid at room temperature
are called oils. Fats and oils are insoluble in water. Fats and oils carry flavour, odour and fat
soluble vitamins. They all have different functional and sensory characteristics.
•
•
•
COMPOSITION
Fats and oils are mixtures of triglycerides. These triglycerides are formed from these
molecules of fatty acids joined to one molecule of glycerol. Each fatty acid is made of
a chain of carbon atoms with hydrogen atoms attached. There are two kinds of fatty
acid: saturated and unsaturated.
Oils provide 100g fat/100g oil i.e. they contain no water. Some oils are ‘hydrogenated’
(hardened or made more saturated) to make them more useful. This process adds
hydrogen to saturate the double bonds in unsaturated fatty acid molecules. This changes
the liquid oil to a solid fat, which can be used in the manufacture of margarine.
•
Fish oils have a high percentage of unsaturated fatty acids. They are normally
hydrogenated to make them solid and for use in manufacturing bakery products.
Fish oils are rich in n-3 fatty acids and vitamins A and D and are used for vitamin
supplements.
•
Vegetable oils may be a rich source of unsaturated fatty acids. They usually contain
natural antioxidants, which resist rancidity. Sometimes a blend of fats is used in a
product to take advantage of the desirable characteristics of several types of fat.
Some oils are rich in n-6 fatty acids (eg sunflower and corn oils). Other oils are rich
in monounsaturated fatty acids (eg olive oil, rape seed oil, groundnut oil).
•
•
Margarines provide approximately 80g fat per 100g.
Spreads. These days a wide variety of spreads exist. They vary in terms of the fat content
and also in terms of the type of oil from which they have been made and whether butter
fat or milk solids have been added. Low and reduced fat spreads have a higher water
content. Low fat spreads are not suitable for frying or baking because of their high water
content.
• Butter is not pure fat, but an emulsion of water in oil ie provides about 80g fat/100g.
• Lard comes from pig’s fat. It is a useful shortening ingredient due to its plasticity.
Dripping is the fat which ‘drips’ from meat being roasted. It has the flavour of meat.
Suet is the fat around the organs of animals such as ox and sheep. It is very solid and
hard. Animal fats are mainly saturated but meat fats are a source of
monounsaturated fatty acids.
CHARACTERISTICS
• Shortening:
• Products such as shortcrust pastry, biscuits and shortbread rely on fats to give their
characteristic crumbly and short texture. The fat coats flour particles, and prevents
moisture absorption which inhibits gluten formation.
•
•
•
•
•
•
•
•
•
Plasticity:
Fats do not melt immediately, but soften over a range of temperatures. This property
is called plasticity, and gives each fat its unique character. The plasticity is due to the
mixture of triglycerides, each with its own melting point. Some fats have been
formulated so that their melting points are low and they can be spread straight from
the fridge, eg soft margarine.
Flavour:
All fats and oils have unique flavours and odours. Some are more suited for
particular purposes than others, eg olive oil for salad dressing (for flavour) and lard
for pastry (due to its blandness).
Retention of moisture:
Some fats can help retain a bakery product’s moisture and increase its shelf-life.
They may also be used to baste food being cooked by dry heat.
STORAGE
Fats should be stored in a cool place, covered, and away from strong odours. They
should be packaged to prevent oxidation.
Oils should be stored at ambient temperature in sealed containers. Oils that have
been used need to be strained to remove impurities to prevent oxidation. Oils that
have been used for deep frying frequently, should be discarded.
4.Meat
COMPOSITION
Meat is muscle tissue from animals. It is made up from long thin muscle fibres. These are
bound together in bundles by thin sheets of connective tissue. Error!
Connective tissue is made up from basic proteins - collagen, elastin and reticulin. Each
protein has specific characteristics and reacts differently when meat is cooked. Collagen is
weakened by heat and forms gelatin, which is soluble. This change helps the meat to become
tender. The two other proteins are not weakened by heat, yet provide elasticity and strength.
•
•
CHARACTERISTICS
Tenderness: Some varieties of meat are tough and may be hard to cut or chew.
Reasons for this include the type of animal, its age, level of activity and the part of
the animal eaten. Tenderness can be improved by:
• Mechanical action - Tenderness is improved by reducing the length of muscle fibres, for
example by mincing, hitting with a tenderising hammer or cutting the meat into chunks.
• Chemical action - Meat tenderizers contain proteolytic enzymes which, when added
to the surface of meat, digest muscle fibre and connective tissue.
• Hydration - An acidic, alkaline or salt solution can increase the water holding
capacity of meat and make it more tender. Acids, eg wine or lemon juice, are often
used to marinade meat before cooking.
• § Colour change: The colour of meat is due to a mixture of pigment in the muscle.
The main pigment is called myoglobin. Muscles contain varying proportions of
pigments. Muscles which are used for physical activity contain large quantities and
are darker in colour. As red meat is cooked the myoglobin changes from a purple red
to a greyish brown in colour.
Nutrition
 § Lean meat is a nutritious food, which in moderate amounts can make a valuable
contribution to intakes of protein, long chain fatty acids, B vitamins, vitamin D, iron and
zinc.
• Protein: 10-20%
• Fat: lean 7.9% (pork), 2.3% (beef )
Fat: 90%
• Minerals: 0.8-1.2%, Ca 7.9mg/100g, Fe (heme)
Meat Nutrition in 100g
Protein
Fat
Ca
Fe
VA (ug) VB1
(mg)
VB2
(mg)
Ch
(mg)
Pork
20.3
6.2
6
3.0
44
0.54
0.10
79
Chicken
19.3
9.4
9
1.4
48
0.05
0.09
106
Pig heart 16.6
5.3
12
4.3
13
0.19
0.48
151
Duck
15.5
19.7
6
2.2
52
0.08
0.22
94
Goose
17.9
19.9
4
3.8
42
0.07
0.23
74
TYPES
• Beef/Veal, eg rump steak, brisket, loin of veal
• Lamb/Mutton,eg chops, shoulder, shank
• Pork/Bacon, eg chops, gammon steak, spare ribs
• Poultry, eg chicken, duck, goose
• Offal, eg liver, kidney, tripe
• Game, eg pheasant, rabbit, venison
6. Milk and milk product
Milk
•
Cows’ milk is the type of milk most commonly consumed. Other types that are also
used are ewes’ and goats’ milk. Most milk undergoes some form of heat processing
such as pasteurisation, sterilisation or ultra high temperature (UHT) treatment. This
is to ensure that any harmful micro-organisms are destroyed before the milk is
consumed and to improve keeping qualities.
•
Milk has been derived from many types of mammals and put to different uses over
the centuries. This has resulted in the development of a number of milk products.
These include butter, cheese, cream and yogurt.
•
Cream is made by separating the fat and solids from milk. It is a fat-in-water emulsion.
When whipping or double cream is whipped it changes from a liquid to a foam. This is
due to the partial denaturation of the proteins, which stabilise the mixture by trapping air.
• Cheese can be classified in a number of ways, for example by the place where it is
produced or the method of production. Generally it is composed of milk solids,
including some water and other ingredients. An enzyme called rennin is used to clot
the milk and produce the milk solids (casein curd) and liquid (whey) which is
drained off. The different kinds of cheese result from different methods of
production and raw ingredients.
Yogurt is milk which has been coagulated and soured by lactic acid. The lactic acid is
produced by the addition of harmless bacteria.
•
Butter is a water-in-oil emulsion made from cream. Its composition is controlled by
law:
•
•
•
•
•
* milk fat, at least 80% but less than 90%
* dry non-fat milk material, no more than 2%
* water, no more than 16%
NUTRITION
Milk and milk products (cheese and yogurt) are important sources of protein, B vitamins
such as riboflavin and B12, and minerals such as calcium, zinc and magnesium. These
days, they are available with a range of fat contents.
Nutrient content in 100g
Human milk
Cow milk
Sheep milk
water
87.6
89.9
88.9
protein
1.3
3.0
1.5
Fat
3.4
3.2
3.5
CHO
7.4
3.4
5.4
En (kj)
272
226
247
Ca(mg)
30
104
82
P(mg)
13
73
98
Fe(mg)
0.1
0.3
0.5
VA
11
24
84
B1
0.01
0.03
0.04
B2
0.05
0.14
0.12
7. Fish
COMPOSITION
•
The structure of muscle in fish is made up from segments of short fibres which give
fish its characteristic flaky texture. These segments are separated by sheets of fine
connective tissue. This substance is very fragile and is easily converted to gelatine.
The combination of short muscle fibres and gelatine gives fish its tenderness, and is
the reason why overcooking will result in fish falling apart.
CHARACTERISTICS

·Fat content: Oily fish have more than 5% fat in their flesh, eg sardine and salmon.
White fish have less than 5% fat in their flesh, eg cod and halibut.
8. Eggs
An egg is made up from 3 main parts: the shell, white and yolk.
Error!
•






As an egg gets older, several changes occur:
·water moves from the white to the yolk
·the yolk structure weakens
·the egg white becomes thinner
·the air space increases
·bacteria may enter through the shell
·a ‘bad egg’ smell occurs due to the production of hydrogen sulphide and related
compounds
Characteristics of fresh and stale eggs
CHARACTERISTICS
• Coagulation: When eggs are heated, the protein in the white and yolk starts to coagulate.
This means that the liquid egg becomes firmer. As heating continues the egg eventually
becomes solid. Boiled, poached, fried and scrambled eggs all demonstrate this process.
The coagulation of eggs makes them suitable for a variety of functions.
• Emulsification: Egg yolk contains lecithin which acts a an emulsifier. It can be used
to stabilise emulsions. Adding egg yolk to a mixture of oil and water prevents the two
liquids from separating. An example of this is mayonnaise which is an emulsion of
oil and vinegar, held together by egg yolk. Industrially manufactured mayonnaise
uses pasteurised egg (which has been heat treated to destroy potentially harmful
micro-organisms), rather than raw egg, to ensure safety.
• Foaming: Whisking egg white incorporates air and produces a foam - a relatively stable
mass of bubbles. If left to stand, the foam will gradually collapse, but when heated the
foam becomes permanent, eg meringue. Whole egg incorporates air less well, but gives
sponge cakes a light texture.
10. Phytochemicals
Zeyuan Deng
 There are many different herbal and botanical supplements on the market, ranging from
ground up herbs you probably never heard of such as the Kava Kava root, to well known
and widely used supplements such as ginseng and garlic. Herbals and botanicals are
supplements that contain extracts or active ingredients from the roots, berries, seeds,
stems, leaves, buds or flowers of plants. It is a common misconception that supplements
made from plants are safe because they are "natural" or "organic".
Classification of phytochemicals
 According to the chemical structures and functional characteristics, the phytochemicals
are classified into: carotinoids, phytosterols 植 物 甾 醇 类 ， saponins 皂 角 苷 ,
glucosinolates 芥子油甙, polyphenols, monoterpenes 单萜, Phyto-oestrogens 雌激素,
sulphides 硫化物, lectins 植物血凝素
Functions of phytochemicls
A
B
Caro-
*
P-sterols
*
Saponins
*
*
G-sinolate
*
*
polyphenol
*
*
M-terpene
*
*
P-oestrogen
*
*
sulphide
*
*
lectins
*
C
D
*
E
F
G
*
H
I
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
A-anticancer, B-anti-bacterium, C-antioxidation, D-anti-thrombus 血 栓 , E-improve immune
ability, F-anti-inflammation 炎症, G-regulate blood pressure, H-decrease cholesterols, I- regulate
blood glucose
1) Flavonoids
Flavonoids are a group of polyphenolic compounds diverse in chemical structure and
characteristics. They occur naturally in fruit, vegetables, nuts, seeds, flowers, and bark and
are an integral part of the human diet.
Generic structure and major classifications
Flavonoids are low molecular weight polyphenolic substances based on the flavan 黄烷 nucleus.
Figure 1 shows the generic structure of flavonoids and the numbering system used to distinguish
the carbon positions around the molecule. The three phenolic rings are referred to as the A, B, and
C (or pyrane) rings. The biochemical activities of flavonoids and their metabolites depend on their
chemical structure and the relative orientation of various moieties on the molecule. Flavonoids
are classified according to their chemical structure. The major flavonoid classes include flavonols
黄酮醇, flavones 黄酮, flavanones 黄烷酮, catechins (or flavanols)儿茶酚, anthocyanidins 花色素,
isoflavones, dihydroflavonols 黄烷酮醇, and chalcones 查耳酮.
Biological Effects
 They have been reported to exhibit a wide range of biological effects, including
antibacterial, antiviral, anti-inflammatory, antiallergic, and vasodilatory actions, In
addition, flavonoids inhibit lipid peroxidation (LPO), platelet aggregation, capillary
permeability, and fragility, and the activity of enzyme systems including cyclo-oxygenase
and lipoxygenase.
Flavonoids exert these effects as antioxidants, free radical scavengers, and chelators of divalent
cations.
 Flavonoids inhibit LPO in vitro at the initiation stage by acting as scavengers of
superoxide anions and hydroxyl radicals. It has been proposed that flavonoids terminate
chain radical reactions by donating hydrogen atoms to the peroxy radical forming a
flavonoid radical. The flavonoid radical in turn reacts with free radicals, thus terminating
the propagating chain. In addition to their antioxidative properties, some flavonoids act as
metal-chelating agents and inhibit the superoxide-driven Fenton reaction, which is an
important source of active oxygen radicals.
Distribution and function in plants
 Over 4,000 types of flavonoid compounds have been identified in vascular plants and
these vary in type and quantity due to variations in plant growth, conditions, and maturity.
Only a small number of plant species have been examined systematically for their
flavonoid content and therefore the identification and quantification of all the types of
flavonoids consumed by humans is incomplete. Plants have evolved to produce
flavonoids to protect against fungal parasites 寄生虫, herbivores 草食动物, pathogens,
and oxidative cell injury.
Dietary intake and food sources of flavonoids
 Ktihnau estimated the average intake of all dietary flavonoids in the USA to be
approximately 1g/day (expressed as glycosides) of which about 170 mg (expressed as
aglycones) consisted of flavonols, flavanones, and flavones.
 The average dietary flavonoid intake in The Netherlands was estimated to be
approximately 23 mg/day (expressed as aglycones) Quercetin was the major dietary
flavonoid (mean intake 16m/day), followed by kaempferol (4 m/day), myricetin (1.4
mg/day), luteolin (0.92 mg/day), and apigenin (0.69 mg/day). The greatest dietary
sources of flavonoids were: tea, 48% of total intake; onions, 29%; and apples, 7%.
The average consumption was: tea, 2 cups/day (294 - 310 mL); onions, 16 - 32 g/day;
and apples, 45 - 71 g/day. Thus, these levels of flavonoid intake were achieved
without unusually high consumption of these foods. Red wine is also a rich sources
of flavonoids and contains approximately 22.5 mg/L (3.8 mg/170 mL glass).
Possible Adverse effects
 Adverse reactions from flavonoids have been reported following administration of
chronic pharmacological doses that exceed the estimated dietary intake of 23 to 170
mg/day. Toxic effects that have been documented from doses of 1 to 1.5 g/day of
flavonoid drugs such as cianidanol include acute renal failure, hemolytic anemia,
thrombocytopenia 血小板减少, hepatitis, fever, and skin reactions. In one study, quercetin
is reported to have induced bladder cancer in rats when consumed at the level of 2% in
the diet.
2) Ginkgo biloba 银杏树
 Ginkgo biloba is an extract from the leaves of the Ginkgo tree, also known as the
Maidenhair tree. The Ginkgo is the oldest living tree species on earth and has been used
medicinally by the Chinese for some 4,000 years.
Claimed health benefits
 Increases blood flow to the brain, theoretically improving cognitive function.
 Enhances memory, especially in people with age-associated memory impairment
problems.
 Alleviates calf muscle blood vessel athersclerosis, thus reducing pain when walking.
Ingredients
 The actual active ingredients in Ginkgo biloba are bioflavonoids and ginkgolides. These
are usually called Ginkgo biloba extract or GBE.
 Dose
 The daily dose of Ginkgo biloba that has been used in research is between 120 and
160mg
Cautions
 Side effects from taking Ginkgo biloba are few and mild with the most severe reports
being gastrointestinal problems, headaches and allergic skin reactions. Very large doses
may cause restlessness, diarrhea, nausea and vomiting.
 It is important to remember that dietary supplements do not have to be manufactured to
any standards, and thus supplements from different manufacturers are likely to vary in
quality.
 There is a distinct lack of scientific data on the safety of herbal supplements when taken
by children and pregnant or breast feeding women. If you fit into these categories do not
take herbal supplements.
3) St. John's Wort
 St. John's Wort is an extract from the herb tops and flowers of the Hypericum perforatum
金丝桃属植物 plant and it is thought that it was first used in Greek and Roman times.
Claimed health benefits
 Symptomatic treatment of mild / moderate depression
 Evidence for health benefits
 The antidepressant action of St John's Wort has been shown in many well conducted
clinical trials. One 4-week, randomized, placebo-controlled, double blind-study in which
39 patients with depression with somatic symptoms were treated with 900 mg Hypericum
extract found that 70% of the treated patients were free of symptoms after 4 weeks. These
symptoms included lack of activity, tiredness, fatigue, and disturbed sleep
 Dose
 300 mg Hypercium three times a day results in therapeutic effects. St John's Wort should
be taken with food.
 Choosing the brand
 The constituent of Hypericum extract that is responsible for the antidepressant effect has
not been identified
Cautions
 St Johns Wort has been associated with gastrointestinal irritations, allergic reactions,
tiredness, and restlessness although the side effects are extremely rare.
 St. John's Wort should not be used with prescription antidepressants
 There is a distinct lack of scientific data on the safety of herbal supplements when taken
by children and pregnant or breast feeding women. If you fit into these categories do not
take herbal supplements.
4) Echinacea 金花菊
 Echinacea, also known as purple coneflower or snakeroot is a prarie flower native to
central North America.
Claimed health benefits :
Stimulates the immune system.
Evidence for health benefits
Echinacea's stimulation of the immune system is well documented in respectable scientific studies,
for example, one double-blind, placebo-controlled trial examined the immunostimulating
influence of an Echinacea preparation on the course and severity of cold-like symptoms in
patients having greater than normal susceptibility to infection. Patients taking the Echinacea were
found to benefit significantly and recover more rapidly than the placebo group.
Dose
 The dosage of Echinacea depends on the potency of the particular preparation. Research
suggests that 8-9 mL of liquid preparations be used daily and that the dosage of capsules
or tablets is 1g 3 times daily. many commercially available capsules sold in the U.S.
contain 380 mg of Echinacea, and therefore 3 capsules should be taken 3 times a day.
Cautions
 There have been no reports of serious reactions to the consumption of Echinacea other
than mild allergic reactions and fever in clinical trials where massive doses were
administered.
 People with kidney disease or disorders should not take it for more than 10 days at a time
due to potential mineral imbalance through excretion. Should not be taken for extended
periods by people with compromised immunity.
5) Garlic
Garlic, or Allium sativum, has been cultivated for thousands of years for its therapeutic benefits.
Garlic was used as a treatment for tumors, headaches, weakness and fatigue, wounds, sores and
infections. It was regarded as a physically enhancing tonic 滋补品, and was used by the first
Olympic athletes as an energizer. The active ingredient is allicin. 蒜素
Claimed health benefits
 Reduces high blood pressure.
 Reduces plasma LDL-cholesterol levels.
 Alleviates blood clotting disorders and athersclerosis.
Dose
At least one clove of raw garlic is required per day to provide 5,000 micrograms of allicin, the
active ingredient. A garlic powder or capsule containing about the same amount of allicin can also
be used.
 Choosing the brand
 The principle active agent in garlic is allicin. When garlic cloves are cut or bruised (like
when chewed), an amino acid in the garlic oil called alliin is converted to the
pungent-smelling allicin by the action of an enzyme
Cautions
The large doses of garlic required for its therapeutic effects have been associated with heartburn,
flatulence 肠胃气胀, gastrointestinal problems and halitosis 口臭. Due to garlic's ability to reduce
blood-clotting time, it should not be taken with aspirin, anticoagulants such as coumadin or
heparin or other blood-thinning botanicals such as Ginkgo biloba, bilberry or cayenne. This could
result in internal bleeding.
6) Ginseng
Ginseng is the most famous Asian herb. Various forms of ginseng have been used in medicine for
more than 7,000 years.
Claimed health benefits
 Stimulates the immune system
 Elevates mood, improves physical and mental performance.
Dose
 The generally accepted safe dose for all of the panax 人参 ginseng species is 100 mg 1-2
times daily. For Siberian ginseng (33% fluid extract), 2-4mL one to three times daily is
recommended.
 It is also a universally accepted practice that the doses be spread out to regular intervals
throughout the day, and that a one - two week abstinence 节制 period should occur every
two to three weeks for panax, and every five to seven weeks for Siberian ginseng.
Choosing the brand
 Different species
 The ginseng family contains five closely related species and one distant cousin that are all
found on the supplement market.
 Chinese, Korean or Asian ginseng (Panax ginseng)
 American ginseng (Panax quinquefolium)
 Japanese ginseng (Panax japonicum)
 Himalayan ginseng (Panax pseudoginseng)
 Dwarf ginseng (Panax trifolium)
 Siberan ginseng (Eleutherococcus senticosus) - the distant cousin
 P.ginseng and E.senticosus are considered the most important medicinal species as most
research has concentrated on them specifically. P.ginseng contains 13 ginsenosides, the
active ingredients in ginseng supplements, which may also be called panaxosides or
eleuthrosides.
Cautions
 Ginseng has adverse drug interactions with warfarin and phenelzine, the MAO inhibitor.
 Overdosing on ginseng can cause gastrointestinal problems, insomnia and hypertension.
 Possible side effects include diarrhea, insomnia, nervousness, nausea, and vomiting,
although side effects are infrequent at recommended doses.
11. Fortified Food
What is food fortification?
 Food fortification, sometimes called ‘enrichment’, refers to the addition of one or more
vitamins or minerals to a food product.
 Addition of nutrients such as vitamins and minerals to foods helps to maintain and
improve the nutritional quality of food supply and can correct or prevent nutritional
problems in the population.
 For example, in Canada, fluid milk fortified with vitamin D has almost eliminated
childhood rickets (softening of bones), and fortification of salt with iodine has decreased
the occurrence of goiter. Mandatory fortification of white flour, enriched pasta and
cornmeal with folic acid has occurred in Canada since 1998 in response to evidence that
folic acid reduces risk of babies being born with neural tube defects.
 Existing regulations state that food products such as bread, cereal, pasta and skim milk
may be fortified with vitamins and minerals in amounts lost during processing. Other
products may be enriched to similar vitamin or mineral levels of foods for which they
commonly substitute. For example, vitamins and minerals may be added to soy beverages,
to obtain amounts that are similar to those in milk. Food fortification is also used to make
sure that foods that are used for special dietary purposes contain appropriate nutrients in
appropriate amounts. Examples of such foods include meal replacements, nutritional
supplements, low sodium foods, gluten-free foods, formulated liquid diets and sugar-free
foods
Regulations for Vitamins and Minerals,
 Vitamins that can be added to foods include A, D, E, K, C, thiamin (B1), riboflavin (B2),
niacin, vitamin B6, folate, vitamin B12, pantothenic acid, and biotin.
 Minerals that can be added to foods include sodium, potassium, calcium, phosphorus,
magnesium, iron, zinc, iodide, chloride, copper, fluoride, manganese, chromium,
selenium, cobalt, molybdenum, tin, vanadium, silicon and nickel.
Are there any health risks connected to food fortification?
 Just as eating too little of a vitamin or mineral can lead to a deficiency, eating too much of
a vitamin or mineral may cause health problems. For example, too much vitamin A can
cause birth defects, too much folate can hide symptoms of a vitamin B12 deficiency
which can result in permanent damage to the nervous system, and too much calcium can
lead to kidney problems.
 The UL is now being used to set an upper limit for nutrient intakes in fortification
regulations.
What are the new policy recommendations?
 1) Vehicles for Fortification :
 The appropriate vehicles for fortification shall consider those that are widely consumed
by the general population. The food vehicles to be recommended to ensure outreach are
salt, rice flour, oil, sugar and processed foods. This shall be determined through food
consumption surveys.
 Fortification should ensure no organoleptic 影响器官感觉的 effects on foods fortified.
2) Targets for Fortification
 Fortification shall target at risk groups as identified in national nutrition surveys in
particular children and women of reproductive age.
3) Legislation
 Mandatory fortification will be implemented through proper legislation to include hard
flour with vitamin A and iron, sugar with vitamin A, edible oil with vitamin A, NFA rice
with iron
 The DOH together with partner agencies shall prepare and submit position papers to
appropriate bodies in connection with its advocacy efforts for the passage of food
fortification bills. Dialogues with government agencies and industry representing the
advantages of fortification and sharing of data which may help in decision making and
planning shall be undertaken.
Standards
 Standards for fortification of staples shall be developed in consultation with the industry
and other partner agencies.
 The Guidelines on Micronutrient Fortification of Processed Foods shall be reviewed and
revised to consider the concerns of all sectors involved in fortification.
Training
 Training courses will be developed for the industry as well as program implementers to
develop their capability on food fortification. This will include among others topics on
technology, quality assurance, hazard analysis of critical control points (HACCP), good
manufacturing practice (GMP).
12. RDA and DRIs
Recommended Dietary Allowances (RDA)
 A. 1940 -- National Academy of Sciences (NAS) established the Committee
of Food and Nutrition under the National Research Council (NRC)
 B. 1941 -- Food and Nutrition Board (FNB).
 1. advise government agencies on issues relating to food and nutrition.
2. first RDA officially published in 1943
3. first RDA made recommendations on kilocalories, protein, calcium, iron, A,
thiamin, C, riboflavin, nicotinic acid, and D.
4. to be published every 5 years.
Definition of RDA :
The levels of intake of essential nutrients that, on the basis of scientific
knowledge, are judged by the Food and Nutrition Board to be adequate to meet
the known nutrient needs of practically all healthy persons.
1. essential nutrients are those that cannot be synthesized by the body
2. relatively little information on what is required.
3. recommendation set only for nutrient in which there is sufficient information
4. when there is some but not complete evidence, the FNB may include the
nutrient on the Estimated Safe and Adequate list
5. healthy persons only

a. does not include persons on prescription drugs
b. does not include high levels of physical activity
D. Evidence used to establish the RDA (in order of importance)
 1. nutrition depletion and repletion studies
2. balance studies
3. biochemical measurement
4. epidemiological studies
5. animal studies
E. Determining the RDA
 1. establish the mean requirement
2. safety margin, 2 standard deviations above mean (96% of all people)
3. energy allowance is based on the estimated mean population
requirement with no added safety factor
F. Purpose and Use of the RDA
 1. standards for food programs
 a. WIC
b. food stamps
c. school lunch program
d. elderly nutrition program
 2. no time interval implied
3. average over 3-5 days assumed
Dietary Reference Intakes (DRI)
 DRIs are recommended amounts of vitamins, minerals and other important
dietary components that individuals need to prevent deficiencies and to
lower their risks of chronic disease.
 Refers to a set of at least four nutrient-based references values
 1.
Estimated Average Requirement (ERA)
 2.
Recommended Dietary Allowances (RDA)
 3.
Adequate Intake (AL)
 4.
Tolerable Upper Level (UL)
Tolerable Upper Limits (UL)
 A Tolerable Upper Intake Level for a specific nutrient is the maximum daily
amount of this nutrient that is safe to consume. Continuing intakes above
this amount pose a risk of adverse health effects - the higher the excess
intake, the higher the risk to an individual’s health.
 1.
the intake value should pose no risk
 2.
the word tolerable was chosen to avoid implying a possible beneficial
effect
Life-Stage Groups
 1.
Infant
a. 0-5 months
 2.
Children
1. 1-3 years
 3.
Adults (Male and Female)

1.
years
9-13 years
b. 6-11 months
2. 4-8 years
2. 14-18 years
5. 51-70 years
3. 19-30 years
4. 31-50
6. > 70 years
 4.
Pregnancy
1. > 18 years
 5.
Lactation
1. > 18 years
2.19-30 years 3. 31-50 years
2. 19-30 years
3.
31-50
years
Food Guide Pyramid
 6 major food groupings, listed in descending amounts
 a. Fats, oils, and sweets (use sparingly)
b. milk, yogurt and cheese (2-3 servings
c. meats, poultry fish, beans, eggs, and nuts (2-3 servings)
d. vegetable (3-5 servings)
e. fruits (3-5 servings)
g. bread, cereal, rice, and pasta (6+ servings)
DRIs
 是在旧标准的营养素平均供给量（RDAs）基础上发展起来的一组每日平均膳
食营养素摄入量的参考值，其中包括4项内容：平均需要量（EAR）、推荐摄
入量（RNI）、适宜摄入量（AI）和可耐受最高摄入量（UL）。
（一）平均需要量（EAR）
 EAR是根据个体需要量的研究资料制订的，是根据某些指标判断可以满足某
一特定性别、年龄及生理状况群体中 50％个体需要量的摄入水平。这－摄入
水平不能满足群体中另外50％个体对该营养素的需要。EAR 是制订 RNI 的
基础。
(二）推荐摄入量（RNI）
 RNI相当于传统使用的 RDA，是可以满足某一特定性别、年龄及生理状况群
体中绝大多数（97％－98％）个体需要量的摄入水平。长期摄入 RNI水平，
可以满足身体对该营养素的需要，保持健康和维持组织中有适当的储备。RNI
的主要用途是作为个体每日摄入该营养素的目标值。
 RNI是以 EAR 为基础制订的。如果已知 EAR 的标准差，则 RNI 定为 EAR
加两个标准差，即 RNI = EAR＋2SD（ SD：标准差）。如果关于需要量变异
的资料不够充分，不能计算 SD 时，一般设 EAR 的变异系数为10％。这样
RNI= 1.2 × EAR 。
（三）适宜摄入量（AI）
 在个体需要量的研究资料不足而不能计算 EAR，因而不能求得 RNI时，可设
定 AI 来代替 RNI 。 AI 是通过观察或实验获得的健康人群某种营养素的摄
入量。例如纯母乳喂养的足月产健康婴儿，从出生到 4~ 6个月，他们的营养
素全部来自母乳。母乳中供给的营养素量就是他们的 AI 值。 AI的主要用途
是作为个体营养素摄入量的目标。
 制定 时不仅考虑到预防营养素缺乏的需要，而且也纳入了减少某些疾病风险
的概念。根据营养“适宜”的某些指标制定的 AI值一般都超过 EAR，也有可能
超过 RNI。
（四）可耐受最高摄入量（UL）
 UL 是平均每日摄入营养素的最高限量。这个量对一般人群中的几乎所有个体
似不致引起不利于健康的作用。当摄入量超过 UL而进一步增加时，损害健康
的危险性随之增大。UL 并不是一个建议的摄入水平。“可耐受”指这一剂量在
生物学上大体是可以耐受的，但并不表示可能是有益的，健康个体摄入量超
过 RNI 或 AI是没有明确的益处的。