Download Vitamin A

BCH 282
Biochemistry of Nutrition
Objectives:
• To define nutrition and related words.
• To identify nutritional requirements.
• To understand Food pyramid.
• To list types of nutrients and relation to health.
• To define malnutrition and its classification.
• To list main malnutrition problems.
• To describe Obesity.
• Nutrition is defined as the science of
food and its relationship to health. Or,
• The process of making use of food.
• It is concerned primarily with the part
played by nutrients in body growth,
development and maintenance .
• Dietetics is the practical application of the
principles of nutrition; it includes the
planning of meals for the well and the sick.
• Good nutrition means “maintaining a
nutritional status that enables us to grow
well and enjoy good health.”
• Nutrients are substances (specific dietary
constituents) that are crucial for human life,
growth & well-being.
• Macronutrients (carbohydrates, lipids, proteins &
water) are needed for energy and cell
multiplication & repair.
• Micronutrients are trace elements & vitamins,
which are essential for metabolic processes.
CLASSIFICATION OF FOODS
•
Classification by origin:
- Foods of animal origin
- Foods of vegetable origin
•
Classification by chemical composition:
- Proteins
–
–
–
–
Fats
Carbohydrates
Vitamins
Minerals
CLASSIFICATION BY
PREDOMINANT FUNCTION
• Body building foods:
• -meat, milk, poultry, fish, eggs, pulses
etc
• Energy giving foods:
• -cereals, sugars, fats, oils etc.
• Protective foods:
• -vegetables, fruits, milk, etc
• Community Nutrition:
Identification of nutritional needs of population
groups and available resources.
• Nutritional Epidemiology:
It is the investigation of the relationship
between diet and disease.
Nutritional requirements
Recommended Dietary Allowances (RDA):
The level of nutrients considered to be adequate to meet the
nutritional needs of all healthy persons.
Knowledge of RDA is necessary to:
•
Assess the nutritional adequacy of diets for
growth of infants, children and adolescents.
•
Maintain health in adults of both sexes and
during pregnancy and lactation.
The adequate diet & Food
Pyramids
Food Group System:
•
Classifies food according to similarity in
nutrient content.
•
Foods placed in each group have a high
nutrient density.
Daily Food guide with Nutrient Pattern and Recommended
Quantity.
Group
Milk and Cheese
Key Nutrients
Calcium,
Protein
Phosphorus,
riboflavin
Meats, poultry,
fish, beans
Protein, Iron
Niacin, Thiamin
Red meat -> Zinc
Egg yolk and liver
-> Vitamin A
Dry beans and Nuts
-> Magnesium
Quantity
Comments
3 cups for
children 4 cups
for teenagers
2 cups for adults
Low-fat milk products
have generally all the
same nutrient content,
however they are
lower in calories and
vitamin A.
2 servings
Serving size: 2-3
ounces
1 ounce of meat
= 1 egg
or ½ cup cooked
beans
1 ounce = 30 gm
Legumes and nuts has
a lower biological
value than meat.
They can be combined
with animal or grain
products to increase
protein quality.
Cholesterol and
vitamin B12 are found
only in animal
sources.
Food Pyramid
Lessons from Food Pyramid:
1. Maintain a healthy weight.
Studies show that the healthiest range
for body weight is when the body
mass index (BMI) is about 17 to 22.
2. Eat good fats and avoid bad fats.
•
•
•
•
•
Good fats are the oils found in nuts, seeds,
grains and fish.
They are high in the unsaturated fats necessary
for good health.
Good fats should contribute 30 to 45% of the
total fat.
Avoid saturated fats (animal fats and tropical oils
e.g. coconut) to minimize the risk of heart
disease.
Trans-saturated fats are mainly found in
margarines and commercial baked foods.
3. Eat whole-grain carbohydrates. Why?
• whole-grain are more nutritious than refined
carbohydrates
• Being more slowly digested
• Place less stress on pancreatic insulin production.
• Sources of whole grain carbohydrates include
whole meal bread, whole wheat, brown rice.
• Avoid white bread, baked goods and pasta made
with white flour.
4. Avoid red meat as a protein source
and emphasize plant proteins.
• Red meat consumption is linked to a variety
of chronic diseases & increases the risk of
hip fracture.
• Animal proteins are usually packaged with
saturated fat.
5. Eat plenty of vegetables and fruits.
•
Potatoes are not included as a vegetable.
•
Dark green leafy vegetables, and fruit are clearly
beneficial.
•
A diet high in fruits and vegetables lowers blood
pressure and cholesterol and reduces the risk of
cancer.
6. Take a multivitamin daily.
•
This recommendation is insurance against
any inadvertent deficiencies.
Mediterranean Pyramid
Main types of Nutrients
Energy Supplying Nutrients:
• Protein
• Lipids
• Carbohydrates
Non-Energy Supplying Nutrients:
• Vitamins
• Minerals
• Water
PROTEINS
• Proteins are complex organic nitrogenous
compounds.
• They also contain sulfur and in some cases
phosphorous and iron.
• Proteins are made of monomers called amino
acids.
• There are about 20 different aminoacids which
are found in human body.
• Of this 8-9 aa are termed “essential” as they
are not synthesized in human body and must
be obtained from dietary proteins.
Protein Needs:
• Adults: 0.8 gm/kg body weight per day
• Excess protein is not used to build more muscle
– If the body needs energy, the extra amino acids
are used for energy
– If the body does not need energy, the extra amino
acids can be converted to fat and stored.
Sources:
• Complete proteins have all essential amino acids
(animal sources)
• Incomplete proteins lack one or more essential amino
acids (plant sources)
Functions of Proteins
• Body building
• Repair and maintenance of body tissues
• Maintenance of osmotic pressure
• Synthesis of bioactive substances and
other vital molecules e.g.
immunoglobulins
Lipids
•
•
Lipids include cholesterol and triglycerides
Fat is necessary for health
Functions
1. Main source of energy (9Kcal/g).
2. Spare protein.
3. Adipose tissue holds the body organs and nerves
in place.
4. Maintain body temperature.
5. Transportation of fat soluble vitamins.
Classification
• Saturated fat:
– Animal foods generally are rich sources
– Palm and coconut oil also are rich sources
• Monounsaturated fat
– Olives, peanuts, and canola oil are rich sources
• Polyunsaturated fat
– Corn, sunflower, cotton seed, and nut oils are rich sources
• Hydrogenated fat
Hydrogenated fat
• Hydrogenation process hardens liquid oils into more
solid margarine.
– It makes unsaturated fat in oil more saturated
– Also it produces an unhealthy type of fat called
“trans fatty acid”
• Saturated fat and trans fatty acids may be harmful to
health
• Baked products and fried foods are often made with
hydrogenated fats
Cholesterol
• Cholesterol is necessary for cell membranes and the
production of vitamin D, bile, and certain hormones
• It is found only in animal foods
• High blood cholesterol levels are associated with
increased risk of heart disease
Fats yield fatty acids and
glycerol on hydrolysis
•
Fatty acid content of different fats ( in per cent)
•
•
•
•
•
•
•
•
•
•
Fats
Saturated Monounsaturated Polyunsaturated
fatty acids
fatty acids
fatty acids
Coconut oil
Palm oil
Cotton seed oil
Groundnut oil
Sunflower oil
Corn oil
Soya bean oil
Butter
92
46
25
19
8
8
14
60
6
44
25
50
27
27
24
37
2
10
50
31
65
65
62
3
Fat requirements
• The WHO Expert committee on Prevention
of Coronary Heart Disease has
recommended only 20 to 30 per cent of
total dietary energy to be provided by fats.
(<30%)
• At least 50 per cent of fat intake should
consist of vegetable oils rich in essential
fatty acids.
Carbohydrates
Functions:
1. Carbohydrate is the main source of energy, providing 4
Kcals per one gram
2. Carbohydrate is essential for the synthesis of certain
non-essential amino acids.
3. Necessary for normal fat metabolism.
4. Necessary for integrity of nerve cells.
5. Lactose allow growth of beneficial bacteria in the
intestine.
6. Important for normal elimination (excretion); fibers
Recommended carbohydrate intake is 55% to 65% of calories,
primarily from starchy foods
Classification of
Carbohydrates
1.
2.
3.
4.
Monosaccharides: glucose &fractose
Disaccharides: Sucrose (G + F)
Oligosaccharides (3-10).
Polysaccharides (11-1000)
a-Indigestable e.g. cellulose
b-partially digestable e.g.raffinose
c-Digestable e.g. starch
The inability of the body to metabolize
carbohydrates properly =DM
Fiber
• Indigestible plant material e.g. cellulose
• Dietary fiber is mainly non-starch polysaccharide
• It is found in vegetables, fruits and grains.
• Soluble fiber swells or dissolves in water
– Rich sources include apples, bananas, citrus fruits, carrots
• Importance:
– Reduces cholesterol absorption
– Slows absorption of glucose
Fiber
• Insoluble fiber remains unchanged in water
– Rich food sources include brown rice, wheat bran,
and whole grain products
• Importance:
• High fiber diet reduces the risk of heart disease,
diabetes type II, diverticulosis, hemorrhoids,
constipation, and possibly colorectal cancer
* Refined foods lose fiber-rich parts during processing
Non-Energy Supplying Nutrients
• Vitamins
• Minerals
• Water
Vitamins
• Regulate growth,
• maintain tissues, and
• help carbohydrates, proteins, and fats release
energy
• Provide no calories (energy)
• Needed in very small amounts
Classes of Vitamins
• Water Soluble: 8 different B vitamins and
vitamin C
• Fat Soluble: Vitamins A, D, E, and K
• Most healthy people do not need supplements;
vitamins can be obtained by eating a variety of
foods
– Supplementation can increase the risk of
consuming toxic high levels
Fat soluble vitamins
Vitamin A
• «Vitamin A» covers both:
– a pre-formed vitamin, retinol, and
– a pro-vitamin, beta carotene, which is converted to
retinol in the intestinal mucosa.
Sources:
– Retinol in liver, code liver oil & eggs (animal sources)
– Beta carotene: Coloured plants e.g. carrot, mango, apricot,
pumpkin,….. (plant sources)
VITAMIN
Sources:
• liver
• milk
• eggs
• spinach
• carrots
• tomatoes
• butter
A
Functions of Vitamin A
• It is essential for normal vision.
• It is necessary for maintaining the integrity and the
normal functioning of glandular and epithelial tissue
which lines intestinal, respiratory and urinary tracts as
well as the skin and eyes.
• It supports growth, especially skeletal growth
• It may protect against some epithelial cancers such as
bronchial cancers.
Vitamin D
• The nutritionally important forms of
Vitamin D in man are:
– Calciferol (Vitamin D2) and
– Cholecalciferol (Vitamin D3)
• Sources: Present in egg yolk + natural
(ultraviolet rays in sunlight).
VITAMIN
•
•
•
•
contains in:
liver
caviar
butter
D
Functions of vitamin D
• Intestine: Promotes intestinal absorption of
calcium and phosphorus
• Bone: Stimulates normal mineralization,
Enhances bone reabsorption, Affects
collagen maturation
• Kidney: Increases tubular reabsorption of
phosphate
Deficiency of vitamin D
Deficiency of vitamin D leads to:
• Rickets in children
• Osteomalacia in adults
Vitamin E
• Antioxidant- Protects RBCs from haemolysis.
• Present in wheat germ and green leafy
vegetables
Vitamin K
• Important for blood coagulation
• Present in leaves of plants + natural (flora).
• Deficiency causes haemorrhagic
manifestations.
VITAMIN
contains in:
• liver
• corn
• eggs
• vegetable oils
E
Water soluble vitamins
Thiamine (B1)
• Function: essential for the utilization of
carbohydrates.
• Present in brewer yeast, beans and legumes.
• Deficiency: Beri-beri
Deficiency of thiamine
• Beriberi may occur in three main forms:
– peripheral neuritis,
– cardiac beriberi,
– infantile beriberi, signs of peripheral
neuropathy.
The Water-Soluble Vitamins
Overview of Water-Soluble
Vitamins
•
•
•
•
•
•
•
Dissolve in water
Generally readily excreted
Subject to cooking losses
Function as a coenzyme
Participate in energy metabolism
50-90% of B vitamins are absorbed
Marginal deficiency more common
Enrichment Act of 1941 and
1998
• Many nutrients lost through milling process
of grains
• Grain/cereal products are enriched
• Thiamin, riboflavin, niacin, folate, iron
• Whole grains contain original nutrients
• Enriched grains still deficient in B-6,
magnesium and zinc
Thiamin
• Contains sulfur and nitrogen group
• Destroyed by alkaline and heat
• Coenzyme: Thiamin pyrophosphate (TPP)
Food Sources of Thiamin
• Wide variety of food
• White bread, pork, hot dogs, luncheon
meat, cold cereal
• Enriched grains/ whole grains
• Thiaminase found in raw fish
Absorption, Transport,
Metabolism of Thiamin
• Absorbed in the jejunum by a carriermediated system
• Transported by RBC in the blood
• Excess quickly excreted in the urine
Function of Thiamin (Fig. 10-2)
Coenzyme: Thiamin
Pyrophosphate (TPP)
• Synthesis of neurotransmitter
• Convert pyruvate to acetyl-CoA
CoA NAD+ NADH + H+
Glucose
Citric
Pyruvate
Acetyl-CoA
CO2
Cycle
Acid
RDA For Thiamin
•
•
•
•
1.1 mg/day for women
1.2 mg/day for men
Most exceed RDA in diet
Surplus is rapidly lost in urine; non toxic
Who is at Risk For Deficiency?
•
•
•
•
Poor
Alcoholics
Elderly
Diet consisting of highly processed foods
Deficiency of Thiamin
• Occurs where rice is the only staple
• Dry beriberi
– Weakness, nerve degeneration, irritability,
poor arm/leg coordination, loss of nerve
transmission
• Wet beriberi
– Edema, enlarge heart, heart failure
Riboflavin
• Coenzymes:
– Flavin mononucleotide (FMN)
– Flavin adenine dinucleotide (FAD)
•
•
•
•
Oxidation-reduction reactions
Electron transport chain
Citric Acid Cycle
Catabolism of fatty acids
Food Sources of Riboflavin
•
•
•
•
•
•
•
Milk/products
Enriched grains
Liver
Oyster
Brewer’s yeast
Sensitive to uv radiation (sunlight)
Stored in paper, opaque plastic containers
Absorption, Transport, &
Metabolism of Riboflavin
• HCL in the stomach release riboflavin
from its bound forms
• Absorption
– Active or facilitated transport during low to
moderate intake
– Passive absorption during high intake
– Increase with intake
• Transported by a protein carrier in the
blood
Functions of Riboflavin
• Accepts electrons
Electron Transport Chain
FAD
FADH2
Succinate
Fumarate
Citric Acid Cycle
• Participates in beta oxidation
• FMN shuttles hydrogen ions and electrons to
into the electron transport chain
RDA for Riboflavin
•
•
•
•
1.1 mg/day for women
1.3 mg/day for men
Average intake is above RDA
Toxicity not documented
Who is at Risk For Deficiency?
– Rare
– Low milk/dairy intake
– Alcoholics
– Long term phenobarbital use
Deficiency of Riboflavin
• Ariboflavinosis
– Glossitis, cheilosis, seborrheic dermatitis,
stomatitis, eye disorder, throat disorder,
nervous system disorder
• Occurs within 2 months
• Usually in combination with other
deficiencies
Glossitis
Niacin
• Nicotinic acid (niacin) & nicotinamide
(niacinamide)
• Coenzyme
– Nicotinamide adenine dinucleotide (NAD)
– Nicotinamide adenine dinucleotide phosphate
(NADP)
• Oxidation-reduction reaction
• Metabolic reactions
Food Sources of Niacin
•
•
•
•
Mushrooms
Enriched grains
Beef, chicken, turkey, fish
Heat stable; little cooking loss
Absorption, Transport and
Storage of Niacin
• Readily absorbed from the stomach and
small intestine
• Absorption: active transport and passive
diffusion
• Transported from the liver to all of the
tissues where it is converted to the
coenzymes
Functions of Niacin
• NAD and NADP participates in 200+ reactions in the
body
2 NAD+
Glucose
2NADH + H+
NAD+
Pyruvate
NADH + H+
NAD+
Isocitrate
Pyruvate
Lactate
NADH + H+
Alpha-ketogluterate
NAD+
NADH + H+
Alpha-ketogluterate
Succinyl CoA
NAD+
NADH + H+
Malate
Oxaloacetate
Citric Acid
Cycle
RDA for Niacin
• 14 NE/day for women
• 16 NE/day for men
Deficiency of Niacin
• Pellagra
– 3 Ds
– Occurs in 50-60 days
– Decrease appetite & weight
• Prevented with an adequate protein diet
• Enrichment Act of 1941
• Only dietary deficiency disease to reach
epidemic proportions in the U.S.
• Who is at risk?
– (Untreated) corn as main staple, poor diet,
Hartnup disease, alcoholics
Dermatitis of Pellegra
Niacin as a Medicine
• 75-100 x RDA can lower LDL and TG and
increase HDL
• Slow/ reverse progression of
atheroscelerosis with diet and exercise
• Toxicity effects
– Flushing of skin, itching, nausea, liver
damage
Pantothenic Acid
• Part of Coenzyme-A
• Essential for metabolism of CHO, fat,
protein
Glucose
Fatty acids
Acetyl-CoA
Alcohol
Amino Acids
Food Sources of Pantothenic
acid
•
•
•
•
•
•
•
Meat
Milk
Mushroom
Liver
Peanut
Adequate Intake = 5 mg/day
Average intake meets AI
Deficiency of Pantothenic
Acid
• Rare
• Burning foot syndrome, listlessness,
fatigue, headache, sleep disturbance,
nausea, abdominal distress
• Alcoholics at risk
• Usually in combination with other
deficiencies
Biotin
•
•
•
•
Free and bound form
Biocytin (protein bound form)
Biotinidase in small intestine
Metabolism of CHO, fat, protein (C
skeleton)
• DNA synthesis
Food Sources of Biotin
• Cauliflower, yolk, liver, peanuts, cheese
• Intestinal synthesis of biotin
• Biotin content only available for a small
number of foods
• Unsure as to bioavailablity of
synthesized biotin
• We excrete more than we consume
• Avidin inhibits absorption
– > a dozen of raw eggs a day to cause
this effect
Functions of Biotin
• Assists in the addition of CO2 to
substances
• Carboxylation of acetyl-CoA to form
malonyl-CoA for the elongation of a fatty
acid chain
• Addition of CO2 to pyruvate to yield
oxaloacetate
• Breaks down leucine
• Allows 3 essential amino acids to be
oxidized for energy
Biotin Needs
• Adequate Intake is 30 ug/day for adults
• This may overestimate the amount needed
for adults
• No Upper Limit for biotin
Who is at Risk For Deficiency?
•
•
•
•
•
•
Rare
High intake of raw egg white diet
Alcoholics
Biotinidase deficiency
Anticonvulsant drug use
Signs & symptoms: skin rash, hair loss,
convulsion, neurological disorders,
impaired growth in children
Vitamin B-6: Pyridoxal,
Pyridoxine, Pyridoxamine
• Main coenzyme form: pyridoxal
phosphate (PLP)
• Activate enzymes needed for metabolism
of CHO, fat , protein
• Transamination
• Synthesis of hemoglobin and oxygen
binding and white blood cells
• Synthesis of neurotransmitters
Food Sources of Vitamin B-6
•
•
•
•
•
•
•
Meat, fish, poultry
Whole grains (not enriched back)
Banana
Spinach
Avocado
Potato
Heat and alkaline sensitive
Absorption and Metabolism of
Vitamin B-6
• Absorbed passively
• All three forms of B-6 are phosphorylated
in the liver
• Binds to albumin for transport in the blood
• B-6 is stored in the liver and muscle tissue
• Excess is excreted in urine
Functions of Vitamin B-6
• Participates in 100+ enzymatic reactions
• Decarboxylation of amino acid
(decarboxylase)
• Transamination reaction (transaminase)
• Structural rearrangement of amino acids
(racemase)
• RBC synthesis
• CHO metabolism
• Lipid metabolism
• Neurotransmitter Synthesis
• Conversion of tryptophan to niacin
RDA for Vitamin B-6
•
•
•
•
•
1.3 mg/day for adults
1.7 mg/day for men over 50
1.5 mg/day for women over 50
Daily Value set at 2 mg
Average intake is more than the RDA
Deficiency of Vitamin B-6
•
•
•
•
•
•
Microcytic hypochromic anemia
Seborrheic dermatitis
Convulsion, depression, confusion
Reduce immune response
Peripheral nerve damage
Who is at risk?
– Elderly
– Alcoholics
• Alcohol decreases absorption
• Destroy the coenzyme form
B-6 As A Medicine?
• PMS
– B-6 to increase the level of serotonin
– Improve depression
– Not a reliable treatment
• Carpal tunnel syndrome
• Toxicity potential
• Can lead to irreversible nerve damage
with > 200 mg/day
Folate (Folic acid, Folacin)
• Consists of pteridine group, paraaminobenzoic acid (PABA), and glutamic
acid
• Coenzyme form: tetrahydorfolic acid
(THFA)
Food Sources of Folate
•
•
•
•
•
Liver
Fortified breakfast cereals
Grains, legumes
Foliage vegetables
Susceptible to heat, oxidation, ultraviolet
light
Absorption, Metabolism of
Folate
• Absorbed in the monoglutamate form with
help of folate conjugase
• Actively absorbed during low to moderate
intake
• Passively absorbed during high intake
• Delivered to the liver where it is changed
back to the polyglutamate form
• Mostly stored in the liver
• Excreted in the urine and bile (enterohepatic
circulation)
Functions of Folate
• DNA synthesis
– Transfer of single carbon units
– Synthesis of adenine and guanine
– Anticancer drug methotrexate
• Homocysteine metabolism
• Neurotransmitter formation
RDA for Folate
• 400 ug/day for adults
• Daily Value is set at 400 ug
Deficiency of Folate
• Similar signs and symptoms of vitamin B12 deficiency
• Pregnant women
• Alcoholics
– Interferes with the enterohepatic circulation of
bile/folate
Megaloblastic Anemia
Neural Tube Defects
• Spina bifida
• Anencephaly
• Importance of folate
before and during
pregnancy
Toxicity of Folate
• Epilepsy
• Skin, respiratory disorder
• FDA limits nonprescription supplements to
400 ug per tablet for non-pregnant adults
• OTC Prenatal supplement contains 800 ug
• Excess can mask vitamin B-12 deficiency
Vitamin B-12
• Cyanocobalamin. methlcobalamin,
5-deoxyadenosylcobalamin
• Contains cobalt
• Folate metabolism
• Maintenance of the myelin sheaths
• Rearrange 3-carbon chain fatty acids so
can enter the Citric Acid Cycle
Food Sources of Vitamin B-12
•
•
•
•
•
•
•
•
Synthesized by bacteria, fungi and algae
(Stored primarily in the liver)
Animal products
Organ meat
Seafood
Eggs
Hot dogs
Milk
Absorption of Vitamin B-12
Therapy for Ineffective
Absorption
•
•
•
•
Many factors can disrupt this process
Monthly injections of vitamin B-12
Vitamin B-12 nasal gel
Megadoses of vitamin B-12 to allow for
passive diffusion
Functions of Vitamin B-12
• Helps convert methylmalonyl CoA to
succinyl CoA (citric acid cycle)
• RBC formation
• Nerve functions
– Maintains myelin sheath
• Megalobalstic anemia
Vitamin B-12 and Homocysteine
(Fig. 10-11)
RDA for Vitamin B-12
• 2.4 ug/ day for adults and elderly
adults
• Average intake exceeds RDA
• B-12 stored in the liver
• Non-toxic
Who is at Risk For Deficiency?
•
•
•
•
Vegans
Breastfed infants of vegan moms
Elderly
Individuals with AIDS or HIV
Deficiency of Vitamin B-12
• Pernicious anemia
–
–
–
–
Never degeneration, weakness
Tingling/numbness in the extremities (parasthesia)
Paralysis and death
Looks like folate deficiency
• Usually due to decreased absorption
ability
• Achlorhydria especially in elderly
• Injection of B-12 needed
• Takes ~20 years on a deficient diet to
see nerve destruction
Vitamin C
• Ascorbic acid (reduced form),
dehydroascorbic acid (oxidized form)
• Synthesized by most animals (not by
human)
• Absorbed by a specific energy dependant
transport system
• Passive transport if intake is high
• Decrease absorption with high intakes
• Excess excreted
Food Sources of Vitamin C
•
•
•
•
•
•
•
•
Citrus fruits
Potatoes
Green peppers
Cauliflower
Broccoli
Strawberries
Romaine lettuce
Spinach
• Easily lost through
cooking
• Sensitive to heat
• Sensitive to iron,
copper, oxygen
Functions of Vitamin C
• Reducing agent (antioxidant)
• Iron absorption
• Synthesis of carnitine, tryptophan to
serotonin, thyroxine, cortiscosteroids,
aldosterone, cholesterol to bile acids
• Immune functions
• Cancer prevention?
• Collagen synthesis
Collagen Synthesis (Fig. 10-12)
Antioxidant
• Can donate and accept hydrogen
atoms readily
• Water-soluble intracellular and
extracellular antioxidant
• Must be constantly enzymatically
regenerated
• Needs are higher for smokers
RDA for Vitamin C
•
•
•
•
•
•
•
90 mg/day for male adults
75 mg/day for female adults
+35 mg/day for smokers
Average intake ~72 mg/day
Fairly nontoxic (at <1 gm)
Upper Level is 2 g/day
Warning to people with hemochromatosis,
oxalate kidney stones
Deficiency of Vitamin C
• Scurvy
– Deficient for 20-40 days
– Fatigue, pinpoint hemorrhages
– Bleeding gums and joints. Hemorrhages
– Associated with poverty
• Rebound scurvy
– immediate halt to excess vitamin C
supplements
• Who is at risk?
– Infants, elderly men
– Alcoholics, smokers