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FOOD QUALITY AND ANALYTICAL CONTROL
Prof. Patrizia Pinelli
a.a. 2015 - 2016
DIETARY PRINCIPLES
LIPIDS
Lipids or fats are a very heterogeneous group of substances of crucial biological importance. They
are water-insoluble organic substances. Lipids are ternary organic compounds, containing carbon
(chemical symbol C), hydrogen (H), oxygen (O2) and, only in some cases phosphorus (P). More in
detail, lipids are molecules consisting of more glycerides, i.e. glycerin (or glycerol) esters with fatty
acids.
The general reaction for obtaining a triglyceride is:
where R, R’, R’’ are the fatty acid chains.
Chemically, therefore, the lipids are composed of long chain carboxylic acids (fatty acids) saturated
or unsaturated, both free or in the form of esters of glycerin. The glycerides are esters of glycerol
combined with fatty acids, usually containing an even number of carbon atoms.
R, R' and R" radical groups can be identical (Triolein if oleic acid is present, Tristearin if there is
stearic acid). The main dietary fatty acids are oleic, linoleic, palmitic and stearic, the first two
unsaturated (contain C = C double bonds) and the last two are saturated (contain C--C single bonds).
By reaction of saturated fatty acids saturated glycerides are obtained, mostly of them solid at room
temperature. In contrast, the glycerides of unsaturated fatty acids are almost all liquid at room
temperature (oils), and, generally, they are of vegetal origin.
The oils are then made up of triglycerides of unsaturated fatty acids (with double bonds between
carbon atoms) and low molecular weight; fats instead contain essentially triglycerides of saturated
fatty acids (with simple bonds between carbon atoms) and high molecular weight.
Saturated lipids are predominantly of animal origin, with the exception of fish oils, while those of
vegetal origin are rich in unsaturated fats. In butter, animal fat of large-utilization, saturated and
unsaturated glycerides are in approximately equivalent amounts.
Some fatty acids are essential (see table 1.3). Beside the triglyceride component, there are more minor
components, such as sterols and fat-soluble vitamins, which are, substantially, the unsaponifiable
fraction.
Table 1.4 Main fatty acids saturated or unsaturated.
Lipids are classified into three main groups: simple lipids, conjugate lipids and derivatives of lipids.
Simple lipids include:
- Fatty acids;
- Neutral fats (mono-, di-and triglycerides)
- Waxes (esters of fatty acids with alcohols with high molecular weight: sterol esters and non-sterol).
Conjugate lipids include:
- Phospholipids (consisting of: fatty acids, phosphoric acid and a nitrogenous base, lecithin is the
most common);
- Glycolipids (compounds from fatty acids combined with a carbohydrate and a nitrogenous base);
- Lipoproteins (lipids combined with protein).
The derivatives of lipids include:
- Glycerol or glycerin
- Sterols (cholesterol, steroid hormones, bile salts);
- Fat-soluble vitamins (vitamins A, D, E, K)
Fats with any prevalence of glycerides solid or liquid have a semi-solid consistency. Fats and oils are
insoluble in water and float on the surface as they have a lower specific weight.
Acrolein is a toxic substance originating from the dehydration of glycerol when the fats have been
heating above 200 °C.
A triglyceride with addition of three molecules of water is cleaved in its constituents (glycerol + fatty
acids) for chemical hydrolysis (heating in diluted acids or alkalis) or enzyme (lipase). This reaction
is known as saponification. When the hydrolysis is carried out with caustic alkali (sodium hydroxide
or NaOH), glycerin and salts of the corresponding fatty acids are obtained, which constitute the soaps
(i.e. sodium stearate).
Oils and fats tend to lose easily their original organoleptic and nutritional value by reacting with the
oxygen from the air; in other words, the rancidity of the fats is an oxidation process, explained by an
initial addition of atmospheric oxygen to unsaturated compounds and is the most frequent alteration
in these molecules.
Lipids are present in all vegetal and animal organisms, they have a high caloric value and, therefore,
are considered as energy nutrients. Differently from the sugars, the use of lipids by our organism is
not immediate. The digestion of lipids is then accomplished through a series of chemical reactions,
where the lipolytic enzymes (lipases) and bile salts are of crucial importance, which catalyze the
breakdown of the ester bond and the intake of water molecules helping the formation of glycerin
molecules and fatty acids. The excessive fat intake can produce an accumulation of adipose tissue
with a tendency to obesity, albeit fats must be present in sufficient quantity in diet since they contain
essential substances for our organism.
The optimal intake of lipids is 30% of total calories through adolescence and 25% in adults; lipids
must also be mainly vegetables, especially as they contain "essential" fatty acids that the human body
cannot synthesize. In particular: linoleic acid, linolenic acid and arachidonic acid (unsaturated fatty
acids). One of the main importance is linoleic acid, which is supposed to represent 2-6% of total daily
energy, as from this the organism is able to synthesize the other two. It is found particularly in the
olive oil (4-15%), in peanut oil (13-28%), sunflower oil (52-66%) and in maize seed oil (34-62%).
Milk is one of the most complete foods; is a white opaque liquid, bearing in suspension of fat globules
of variable size and granules of tricalcium phosphate, and, in pseudosolution, caseinogen protein,
lactose, lactoglobulin (proteins constituted by acid glutamic acid, leucine, lysine and aspartic acid),
other proteins, other organic substances, and minerals. Leaving the milk in open air, it is observed on
the surface a layer of a so-called yellowish cream, which differs quantitatively from the milk to a
higher concentration of fat (18-40%) and minor protein and lactose. The butter derives from this
cream and contains 83.4% of lipids. With the process of milk homogenization this effect occurs no
longer.
The main milk production is destined for processing into cheese, obtained from whole milk, partially
or completely skimmed milk, or cream, by coagulation with rennet or ferments and salt.
Amid vegetal oils, the most valuable is the extravirgin olive oil, obtained by mechanic pressing the
olive fruits (Olea europaea L.). The olives crushed on the mill undergo the breaking of the membrane
cell delivering the oil. The paste product is then pressed to be separated in a liquid part (olive oil) and
a solid one (pomace).
Finally, the margarine, a fat food industry invented by the French pharmacist Hyppolite Mouries
which studied the possibility of creating a fat food from beef tallow to obtain a fat cheaper than butter
and most easily storable. Currently, the margarines are almost entirely derived from planthydrogenated fats.
Phospholipids (Lecithin)
The cells of human body are surrounded by a very important type of lipid, called phospholipids.
Phospholipids consist of a hydrophilic (“water loving”) head and a hydrophobic (“water fearing”)
tail. Phospholipids like to line up and arrange themselves into two parallel layers, called
a phospholipid bilayer. This layer makes up your cell membranes and is critical to a cell's ability to
function.
Phospholipids are made of two fatty acids (long chains of hydrogen and carbon molecules), which
are attached to a glycerol 'head'.
The glycerol molecule is also attached to a phosphate group, and this is the hydrophilic part of the
molecule. The 'tail' ends of the fatty acid chains opposite the glycerol is the hydrophobic part of the
molecule.
The most important function for a phospholipid is to form the phospholipid bilayer. In this bilayer,
the phospholipids are arranged so that all the hydrophilic heads are pointing outward and the
hydrophobic tails are pointing inward. This arrangement comes about because the areas both outside
and inside your cell are mostly water, so the hydrophobic tails are forced in.
Since lipids do not get broken down by water, the bilayer provides a barrier around the cell and only
lets in certain molecules. Some small molecules, like carbon dioxide and oxygen, pass through the
phospholipid bilayer quite easily. This is good because these gases are involved in cellular respiration,
which is how your body makes energy from the food you eat.
Lecithin is a generic term to designate any group of yellow-brownish fatty substances occurring in
animal and plant tissues composed of phosphoric acid, choline, fatty acids, glycerol, glycolipids,
triglycerides, and phospholipids.
Lecithin is usually available from sources such as soybeans, eggs, milk, marine sources,
rapeseed (canola), cottonseed, and sunflower.
It has low solubility in water, but is an excellent emulsifier.
A major source of lecithin is soybean oil.
To make soy lecithin, soybean oil is extracted from the raw soybeans using a chemical solvent
(usually hexane).
Because of the EU requirement to declare additions of allergens in foods, in addition to regulations
regarding genetically modified crops, a gradual shift to other sources of lecithin (e.g., sunflower oil)
is taking place.
Soy lecithin is also being recommended and consumed as a dietary supplement. There is a growing
body of research supporting its use for improving blood lipids, reducing inflammation, and treating
neurological disorders. For instance, one study found that after 2 months of supplementing with 500
mg of soy lecithin per day, total cholesterol levels fell by 42% and LDL levels decreased by 56%.
Sterols
Steroids are just one particular type of hormone, produced by our bodies, in particular cholesterol,
estrogen, cortisol, and testosterone.
Cholesterol is a waxy substance that comes from two sources: your body and food. Your body, and
especially your liver, makes all the cholesterol you need and circulates it through the blood. But
cholesterol is also found in foods from animal sources, such as meat, poultry and full-fat dairy
products. Your liver produces more cholesterol when you eat a diet high in saturated and trans fats.
The most important sterol widespread in the animal kingdom is cholesterol. The sterols of plant
origin, sitosterol and stigmasterol, are called phytosterols. The presence of cholesterol or
phytosterols indicates, therefore, the origin from an animal or vegetable fat matter and can reveal
mixtures of fats from different origin.
Cholesterol:
is the main steroid compound among those present in the human body.
is present in biological membranes, and helps to give them the right characteristics of
flexibility;
is necessary for the biosynthesis of other steroid hormones, bile acids, and vitamin D.
Cholesterol, an insoluble molecule in human plasma, is transported in the blood in the form of soluble
complex with LIPOPROTEIN.
Lipoproteins are a class of proteins further divided into subclasses based on their density. The two
major subclasses are that of LDL (low density lipoprotein) and HDL (high density lipoprotein).
LDL carry cholesterol from the liver, where it is synthesized or stored, to the cells that use it. HDL
pick up excess cholesterol from various tissues and lead it back to the liver where it is broken down
and eliminated. Excess cholesterol can form plaque between layers of artery walls, making it harder
for your heart to circulate blood. Plaque can break open and cause blood clots. If a clot blocks an
artery that feeds the brain, it causes a stroke. If it blocks an artery that feeds the heart, it causes a heart
attack.
There are two types of cholesterol: "good" and "bad". Too much of one type — or not enough of
another — can put you at risk for coronary heart disease, heart attack or stroke. It's important to know
the levels of cholesterol in your blood so that you and your doctor can determine the best strategy to
lower your risk.
High cholesterol is one of the major controllable risk factors for coronary heart disease, heart
attack and stroke.
If the blood cholesterol rises, so does the risk of coronary heart disease. If there are other risk factors
such as smoking, high blood pressure or diabetes, this risk increases even further. Cholesterol levels
can be also affected by age, gender, family health history and diet.
When too much LDL (bad) cholesterol circulates in the blood, it can slowly build up in the inner
walls of the arteries that feed the heart and brain.
Together with other substances, cholesterol can form a thick, hard deposit called plaque that can
narrow the arteries and make them less flexible. This condition is known as atherosclerosis.
Causes of Cholesterol
•
Sedentary lifestyle, which is devoid of any exercise.
•
Eating a diet rich in saturated fat and cholesterol
•
Cholesterol levels tend to increase as the age. It is ideal to take a lipid profile test once you attain
40 years of age to determine cholesterol levels.
• Poor control of diabetes will result in increase of cholesterol levels.
• Smoking and consumption of alcohol regularly will result in increase of bad cholesterol levels.
Cholesterol-Fighting Foods
EXTRAVIRGIN OLIVE OIL
FISH AND ω-3 FATTY ACIDS
OAT CEREALS
CEREALS WITH FLAXSEED
WHOLE GRAIN CEREALS
FRUITS
NUTS
BEAN & PEAS
In Table 1.5 the cholesterol levels is highlighted in many dairy products.
Table 1.5 Cholesterol levels in many dairy products.
HYDROGENATED LIPIDS
Hydrogenated lipids are obtained by transformation of highly unsaturated vegetable oils in solid
vegetable fats (margarine) by catalytic hydrogenation of the double bonds. The hydrogenation
reaction is called “reduction”. The reduction of the fatty acid chains increases the hardness
(consistency) of the oils.
The hydrocarbon chains of the triglycerides can be changed to obtain products of desired consistency.
For example, from vegetable oils (containing mostly unsaturated fatty acids, then liquid at room
temperature) solid fats can be obtained and used as substitutes for butter.
As an example, margarine, obtained by partial reduction of the oils of corn, soybeans, cotton and
peanuts.
To hardened oils of plant origin, some coloring substances (e.g. beta-carotene), flavoring and
emulsifiers can be added, to obtain a product very similar to butter of animal origin.
Today there is a tendency by the big Companies to substitute margarine with palm oil with high
concerns about its environmental sustainability.
A large proportion of palm oil expansion occurs at the expense of biodiversity and ecosystems in the
countries where it is produced. Currently, a third of all mammal species in Indonesia are considered
to be critically endangered as a consequence of this unsustainable development that is rapidly
encroaching on their habitat.
One animal of particular importance according to conservationists is the orangutan, which has
become a charismatic icon for deforestation in Borneo and Sumatra. Over 90% of orangutan habitat
has been destroyed in the last 20 years, and as such, is considered “a conservation emergency” by the
UN. Estimated 1,000-5,000 orangutans are killed each year for this development. The orangutan is a
keystone species and plays a vital role in maintaining the health of the ecosystem. An example of this
being the spread of rainforest seeds in Indonesia, many of which can only germinate once passed
through the gut of an orangutan, hence this primate is essential for the existence of the forest. But the
orangutan is not the only species affected by palm oil development; their situation represents the story
of thousands of other species facing the same fate in South-East Asia.
Deforestation for palm oil production also contributes significantly to climate change. The removal
of the native forests often involves the burning of invaluable timber and remaining forest
undergrowth, emitting immense quantities of smoke into the atmosphere and making Indonesia the
third highest greenhouse gas emitter in the world.
NUTRITIONAL USES OF LIPIDS
Lipids are concentrated sources of energy (9.45 kcal/g), but they also have other functions:
1) provide means whereby fat-soluble nutrients (e.g., sterols, vitamins) can be absorbed by the body
2) structural element of cell, subcellular components
3) components of hormones and precursors for prostaglandin synthesis
Biological functions of lipids
It is now known that lipids play a much more important role in the body than previously believed. It
was previously known that lipids played the role of storage of energy or forming cell membranes
alone. Researchers have found that lipids have a much more diverse and widespread biological role
in the body in terms of intracellular signaling or local hormonal regulation etc.
Lipids are synthesized in the body using complex biosynthetic pathways. However, there are some
lipids that are considered essential and need to be supplemented in diet.
The essential fatty acids play also an important role in the transport and metabolism of cholesterol.
The needs of essential fatty acids in the human organism is 4-14 g/day, quantity provided by about
30 g of butter or 20 g of olive oil.
Plasma lipids are essentially in the form of cholesterol, phospholipids, and triglycerides. Lipids are
stored in adipose tissue and are released in the form of free fatty acids (FFA); they circulate into the
plasma and are used by the liver, heart and muscle tissues. Phospholipids are vital constituents of the
cells and are essential components of the brain and nervous tissues. Cholesterol is widespread in bile,
adrenal glands and nervous tissue, and is a component of cell membranes together with phospholipids.
Finally, it is a precursor of bile acids, steroid (sexual and adrenocortical) hormones.
The human organism takes normally a small amount of exogenous cholesterol (derived from food),
and it is mainly synthesized in most tissues, especially in the liver (endogenous cholesterol). More
than three quarters is excreted in the feces in the form of bile acids.
The excess cholesterol in blood (hypercholesterolemia) has a primary role in the pathogenesis of
vascular sclerosis and lithiasis. At birth, cholesterol values are very low, increasing in the early days
of life (about 1.85 g/L of blood in children and 2.0 g/L in adults). The biochemistry of cholesterol,
however, varies according to genetic factors and habits related to the life style such as diet,
inactiveness, smoking, excessive consumption of caffeine.
Insoluble in blood, it is carried by some proteins to form complex macromolecules called lipoproteins.
The lipoprotein are present in the blood from 10% level as VLDL (Very Low Density Lipoprotein),
to 60-65% as LDL (Low Density Lipoprotein), also known as "bad cholesterol", and about 25% are
present as HDL (High Density Lipoprotein), also known as "good cholesterol". Actually, when the
rate of LDLs in the blood is high, cholesterol is deposited on the artery's walls, forming fatty plaques
(atheroma). These plaques obstruct the blood flow that carries oxygen to the muscles, determining
the atherosclerosis syndrome. On the contrary, HDLs do not have any atherogenic action, conversely
being protective against cardiovascular disease, since they transport cholesterol from peripheral cells
to liver to eliminate bile salts in the form of bile and steroids.
Cholesterol amounts vary in animal fat, and are less in vegetable ones. The daily intake of cholesterol
should not exceed 500 mg.
Vegetable oils are very important in a balanced diet, for their content of unsaturated fatty acids, highdensity liquids, cleaning artery vessels, and preventing atherosclerosis. The opposite is the case for
saturated fatty acids, solid, mostly of animal origin, that are detrimental for arteries.
Essential fatty acids are unsaturated fatty acids mainly found in plant fats and, in optimal ratio, in
olive oil:
- Linoleic acid 3-21%;
- Linolenic acid 0.2-1.5%;
- Arachidonic acid from 0.1 to 0.7%
Actually, only linoleic acid can be defined “essential”, since with an adequate intake of this latter
(2-6% of total daily energy), the body is able to synthesize the other two acids. Beside the olive oil,
the linoleic acid is present in high concentration in peanut oil (52-66%) and in the oil of corn seeds
(34-62%). Therefore, the daily diet should provide essentially vegetable fats.
Essential fatty acids belong also to omega-3 and omega-6 classification (see the previously reported
Table 1.4).
Main functions of omega-3 fatty acids
• Lower plasma levels of triglycerides
• They have a low efficacy in reducing total cholesterol levels in the blood (modest
hypocholesterolemic effect)
• Slightly increase the concentration of "good" cholesterol (HDL)
• Increase blood fluidity significantly, reducing the risk of coronary heart disease
• Anti-atherogenic, anti-inflammatory and antithrombotic actions.
Main functions of omega-6 fatty acids
• Reduce the concentration of cholesterol in the blood, lowering both the fraction "bad" (LDL) and
“good” (HDL)
• Low efficacy in reducing plasma levels of triglycerides (modest hypotriglyceridemic action)
• If present in excess with respect to the omega-3, however, they are responsible for a series of side
effects (increase of allergic and inflammatory reactions, increase of blood pressure, platelet
aggregation and, therefore, cardiovascular risk).
CARBOHYDRATES
Carbohydrates, or sugars, are key organic constituents of living matter; mainly represented by
polymers synthesized in the plant world as "support material" (cellulose) or "spare" (starch), and in
the animal world as a "reserve" material (glycogen).
Carbohydrates are present only in foods of plant origin, with the exception of milk and its derivatives;
they can be differentiated from a chemical point of view, as follows:
• simple sugars (monosaccharides), low molecular weight, water soluble and with sweet taste;
• complex sugars (oligosaccharides and polysaccharides), high molecular weight, insoluble and
devoid of sweet taste.
From a nutritional point of view, we can distinguish:
• available carbohydrates, sugars and polysaccharides such as starch, with nutritional value as
digestible,
• unavailable carbohydrate, such as oligosaccharides and non-digestible polysaccharides (cellulose,
hemicellulose, pectin, etc..) and, finally, the so-called dietary fibers.
Glucose, starch, cellulose and glycogen, are the most representative carbohydrates. These molecules
are an important supply of energy for the normal functioning of human body, and are crucial in
supporting plant tissues (cellulose in wood, cotton, flax) and in some animals (glycogen or animal
starch). They are the main energetic principles in plants where are accumulated as starch, whereas in
the form of glycogen in animal organisms. From the chemical point of view, carbohydrates are ternary
organic compounds, formed by three elements: carbon, hydrogen and oxygen.
Simple sugars
Depending on the number of carbon atoms, we can distinguish among monosaccharides, trioses,
tetroses, pentoses and hexoses. For instance, trioses have three carbon atoms, and hexoses have six.
The most important and abundant monosaccharide is glucose, which constitutes the basic unit of all
other complex carbohydrates, and having six carbon atoms in its molecule is classified as "hexose".
Glucose, transported to the cells of different tissues from the bloodstream, is oxidized to carbon
dioxide and water. Simple glucose is found in fruits, vegetable extracts, honey and in the blood,
where, in physiological conditions, is approximately 0.6 - 1 g/L amounts (normal glycemic).
This concentration is kept constant by insulin, an important hormone secreted by the Langerhans
Islands located in the pancreas; it controls the metabolism of glucose promoting the synthesis of
glycogen in liver and muscles, enhancing glucose oxidation to carbon dioxide and water in the tissues,
and, finally, preventing the formation of fats and proteins.
The lack of this hormone, as its insufficient production, determines an increase in blood glucose levels
and the presence of glucose in the urine. This disease is known by diabetes mellitus.
The diabetic will have to pay particular attention to diet, and must introduce glucose or sugar in
controlled amounts. Glucose has to be replaced with other sugars, as fructose, a monosaccharide
having the same molecular formula but different structure.
The following table shows the main saccharides:
Table 1.6
Saccharide
Glucose
Fruttose
Glucose + Fructose = Sucrose
Glucose + Fructose = Maltose
Glucose + Galactose = Lactose
Starch
Glycogen
Cellulose
Molecular Formula
Type
C6H12O6
C6H12O6
C12H22O11
C12H22O11
C12H22O11
(C6H10O5)n
(C6H10O5)n
(C6H10O5)n
Monosaccharide
Monosaccharide
Oligosaccharide
Oligosaccharide
Oligosaccharide
Polisaccharide
Polisaccharide
Polisaccharide
Combining 2-3 molecules of monosaccharides, disaccharides and trisaccharides are obtained.
The sugar commonly used at home as a sweetener is sucrose, a disaccharide coming from the union
of a molecule of glucose and one of fructose after removal of a water molecule (molecular formula
C12H22O11). Sucrose is naturally found in many plants, and it is industrially extracted from cane sugar
or beet sugar, this latter in European areas. Other important disaccharides are maltose and lactose.
The natural product, which more than any other can be considered as a sweetener is the honey,
consisting of a highly concentrated aqueous solution of simple sugars, with prevalence of fructose
and sucrose, in addition to small amounts of gummy substances, albuminoid and waxy, organic acids,
ethers, minerals (iron, calcium and phosphorus), vitamins B2, C and niacin.
Complex carbohydrates
The origin of the carbohydrates in the Plant Kingdom is a result of the photosynthesis.
In plant leaves carbon dioxide of the air combines with water coming from the roots or present on the
plant to synthesize glucose; n glucose molecules are able to combine with each other and give rise to
cellulose, the organic compound widespread in Nature. In particular, many molecules of glucose (a
simple sugar) can join forming the cellulose (a complex carbohydrate, polysaccharide), the main
component of the cell wall of the plants, at least one third constituent of plant material. The glucose
molecules can be combined, also, in a different structure, giving rise to starch, which differs from
cellulose only for the spatial arrangement of the glucoside bond.
The starch accumulates mainly in seeds, as it is a reserve material serving as nourishment for the
growth of new plants. It is included in plant cells in the form of white granules, whose form and
dimensions are characteristics of the individual plant and serve precisely to distinguish the origin of
a starch (wheat, corn, potato, barley ...). Starch is formed for about 20% of a fraction soluble in water
and of 80% of an insoluble fraction: the first is called amylose, the second amylopectin. Starch is a
carbohydrate of greater importance for the power supply because it is spread in all seeds and,
especially, in cereals and legumes. It provides a readily usable energy, and is easily digested by
humans, unlike cellulose. This latter, which is contained in small amounts in almost all fruits and
vegetables is poorly digestible by the human body. The starch, when ingested, is hydrolyzed and,
then, broken down into glucose units. Glucose is carried by blood to the liver, where more molecules
recombine to form glycogen. Bread and pasta are highly starchy foods. The bread is the first and most
important food of man, obtained by kneading wheat flour with water and yeast, followed by baking
dough.
Classification of sugar
Simple sugars are monosaccharides and disaccharides; when glucose units are 2-10, they are also
named oligosaccharides; complex carbohydrates are named polysaccharides (see the following
scheme).
Mono- and disaccharides are water-soluble, have crystalline structure and sweet taste. Depending on
the number of carbon atoms present in the molecule, mono saccharides are divided into tetroses,
pentoses and hexoses, with, respectively, 4, 5 and 6 carbon atoms. The three most important dietary
monosaccharides are glucose, fructose and galactose, all three hexoses and isomers (same molecular
formula, different arrangement of atoms in space). From glucose, the human organism is able to
synthesize two pentoses: ribose and deoxyribose components of ribonucleic acid (RNA) and
deoxyribonucleic acid (DNA), essential for protein synthesis.
The glucose molecules that form the starch are differently combined in structure with respect to
cellulose, differing for the spatial arrangement of the glucoside bond, between two glucose units. As
previously said the starch is accumulated mainly in plant seeds and constitutes a reserve material,
which will be used as a nourishment for the growth of new plants. Small amounts of cellulose are
present in fruits and vegetables. Cellulose is indigestible by human body due to the lack of the specific
enzyme (cellulase), but its presence in food, along with other fibers, it is still important because it
increases the peristaltic movements of the intestine, increases fecal bulk and therefore improves
digestion, thus facilitating the evacuation.
Glucose, starch and cellulose are the most representative carbohydrates in Nature, all coming from
the synthesis of carbon dioxide with the water, in the presence of chlorophyll, thanks to the influence
of solar energy (photochemical reaction = photosynthesis).
Glucose is the sole source of usable energy from the cells of the central system, especially of the
brain.
Fructose or fruit sugar is the sweetest monosaccharide, contained mainly in cherries, pears,
strawberries and oranges. It is combined with the glucose in honey and ripe fruit to give sucrose.
Fructose is levorotatory, it means that rotates polarized light to the left (experiment with a
polarimeter). It is a glucose isomer.
The galactose does not exist free in Nature; it is produced by the hydrolysis of lactose and converted
into glucose during its intestinal absorption. The genetic deficiency in infants of galactose-1phosphate uridyl transferase, an enzyme that converts galactose into glucose, causes a metabolic
disease known as galactosemia, which produces an abnormal increase of galactose in blood,
responsible of a severe mental retardation.
Sucrose, lactose and maltose are three disaccharides most important from the nutritional point of
view. The disaccharides hydrolysis reaction occurs by water vapor under pressure, or by weak acid
or alkali or, finally, by enzymatic action. By hydrolysis, two monosaccharides can be obtained.
In some cases, this hydrolysis reaction is called inversion, since the mixture of products resulting
presents an optical rotation (the plane of polarized light in a polarimeter) contrary to that of departure.
For example, sucrose is dextrorotatory, while the resulting mixture of glucose and fructose is
levorotatory (because fructose does divert the plane of polarized light to the left more than the glucose
deviates it to the right).
Heated over 200 °C the disaccharides give rise to an amorphous mass, of dark color, water-soluble,
which in the case of sucrose takes the name of caramel.
Sucrose is the most common sugar of food. It is formed by the union of a glucose molecule with a
fructose by the elimination of a water molecule. Industrially is obtained from sugar beet or cane sugar
containing it to the extent of 15-20%. It comes in the form of white crystals, water soluble, sweet
taste, and melting point at about 180 °C.
Lactose is found in mammal milk at varying rates: on average 4.5% in cow’s milk; 4.9% in sheep’s
milk; 6.5% in that of woman. It has low sweetening power, so it is used mainly for the production of
reconstituted milk and some pharmaceutical preparations. It occurs in crystals, water soluble, and
melting point at about 202 °C.
Maltose is composed by two glucose molecules, which can be released by acidic or enzymatic
hydrolysis (maltase). It is produced in the process of germination of cereals, while in the human body
is formed from starch, together with dextrin, by the action of diastase, a mixture of amylolytic
enzymes derived from malted barley.
Polysaccharides are formed by several (up to 2000) monosaccharide molecules, generally hexoses,
forming long chains, united by the same glycosidic bond, straight (in the portion of amylose) or
branched (in the portion of amylopectin). They both are poorly or insoluble in water, and do not have
a sweet taste. From the union and repetition of a single monomer, the D(+) - glucose, different
structures through a different glycosidic bond can be produced, i.e. starch or cellulose. Their
hydrolysis can also take place gradually, with the formation of products of partial hydrolysis, as
dextrin starch (destrins).
The starch, the reserve carbohydrate of plants, is widespread in the plant kingdom. The pure
compound is in the form of white amorphous powder, insoluble in cold water and alcohol. It consists
of granules, structurally different depending on the plant material, (those of wheat starch are ovoid,
while those of rice are smaller and prismatic); therefore, we can trace the origin of the flour by the
morphological examination of the starch granules (see starch grain identification by Optical
Microscopy, Experimental Section).
Cellulose is the main constituent along with lignin of cell walls in plants. It is insoluble in all common
solvents, and very resistant to most chemical agents. Cellulose is not digested by human body for the
lacking of the specific enzyme. It is broken up into glucose by the action of hot mineral acids; finally,
it constitutes the raw material for paper’s manufacture.
Glycogen is the carbohydrate reserve material of animals and is found in the liver and muscles. It is
in the form of white powder, insoluble in alcohol and ether, water-soluble. Totally hydrolyzed gives
glucose, and partially hydrolyzed gives maltose. Its structure is similar to amylopectin, with a greater
degree of branching.
Function and metabolism of carbohydrates
As nutritional value, carbohydrates are the most important principles for the intake of energy,
because, although having an energy value higher than that of proteins (4 kcal/g), they produce energy
more readily, since their metabolism begins already in the mouth, thanks to the salivary enzyme,
ptyalin. Muscle contraction can be transformed into mechanical work for only 20-25%, then 4 kcal
(chemical energy) must be provided to human engine so that can be transformed into a work
(mechanical energy).
Classification of energy foods (mainly because they provide energy):
1. Cereals and their derivatives (bread, pasta, polenta, rice, etc.), mainly carbohydrate, because they
provide quick energy use. For example, the common bread contains 61.3% carbohydrates and, then,
develops 277 kcal/100 g; semolina pasta contains 74.6% carbohydrates and, then, develops 373
kcal/100 g.
2. Fats (including vegetable oils), because they provide a high input of energy (9 kcal / g).
Humans ingest more than 50% of the daily energy in the form of carbohydrates (mono, di and
polysaccharides). The main function of carbohydrates is to provide energy to human body. Therefore,
a part of glucose is used to meet immediate energy needs, a part is deposited in the form of glycogen
in the liver and muscles, and the remaining portion is converted into fat and deposited in adipose
tissue.
Carbohydrate’s amount in human body stored as glycogen is very small (about 365 g: 110g in liver ,
245 g in muscles, and 10 g in extracellular fluids). This reserve could ensure an amount of energy
equal to about 1368 kcal, sufficient for up to 13 hours of moderate activity. Therefore, human body
needs carbohydrates regularly to meet the constant demand of energy.
Muscle glycogen is a source of energy only for processes occurring into muscle cells. In fact, muscle
can not produce glucose directly, because this tissue does not possess the enzyme responsible for this
conversion. Conversely, during muscle contractions glycogen is converted to lactic acid, which is
then converted into glucose.
Glucose derived from liver glycogen may be a source of energy for all the body's cells.
In addition to the crucial energetic action, carbohydrates perform specific regulatory functions:
• Regulation of lipid and protein metabolism
• Protection and liver detoxification
• Energy reserve in the heart muscle
Furthermore, the cellulose present in dietary fiber (see the diagram below) helps the bolus transit in
the intestine and, therefore, facilitates digestion.
If the daily carbohydrate intake is insufficient, the body uses proteins or lipids for its immediate
energy needs. However, when lipids are used in large quantities for energy purposes, large amounts
of ketones are formed (acetone, acetoacetic acid), causing a pathological affection (ketosis),
characterized by the presence of acetone in the urine. Hence the importance of a daily energy intake
coming from the correct percentages of the three different nutrients.
If energy demand is lacking, glucose is converted into glycogen, but this spare capacity is limited, so
this excess of sugar is converted to fat (lipogenesis) and deposited as such. Insulin increases the
penetration of glucose into tissues and lowers the amount of free glucose in blood (glycemia). The
ingestion of glucose stimulates the secretion of insulin from the pancreas, while the cortisone
decreases glucose's utilization.
Available and unavailable carbohydrates
This classification arises from the consideration that not all carbohydrates present in food can be
metabolized, as well as amidst the available carbohydrate can definitely include starch and simple
sugars such as fructose, glucose and sucrose, while appearing definitely included among the
unavailable carbohydrates, cellulose, hemicellulose, and more generally all those carbohydrates
present in food and that can be included in what is defined as soluble dietary fiber.
Resistant starch (RS)
Resistant starch is a type of starch that isn’t fully broken down and absorbed, but rather turned into
short-chain fatty acids by intestinal bacteria.
This may lead to some unique health benefits. To get the most from resistant starch, choose whole,
unprocessed sources of carbohydrate such as whole grains, fruits, vegetables, and beans/legumes.
Thus, resistant starch is so named because it resists digestion.
While most starches are broken down by enzymes in our small intestine into sugar, which is then
absorbed into the blood, we can’t fully absorb all kinds of starch.
Some starch — known as resistant starch (RS) — isn’t fully absorbed in the small intestine. Instead,
RS makes its way to the large intestine (colon), where intestinal bacteria ferment it.
RS is similar to fibre, although nutrition labels rarely take RS into account.
However, RS still plays an important role in our diets even though we don’t necessarily absorb it.
When RS is fermented in the large intestine, short chain fatty acids (SCFA) such as acetate, butyrate,
and propionate, along with gases are produced. SCFAs can be absorbed into the body from the colon
or be used by colonic bacteria for energy.
Evidence suggests that SCFAs may benefit us in many ways. For instance, they:
stimulate blood flow to the colon
increase nutrient circulation
inhibit the growth of pathogenic bacteria
help us absorb minerals
help prevent us from absorbing toxic/carcinogenic compounds
The amount of SCFAs we have in our colon is related to the amount and type of carbohydrate we
consume.
In a Research Review on processed vs. whole foods, researchers found that less-processed foods
offered less energy than refined foods. In other words, although whole and processed foods may
contain the same amount of calories, we absorb fewer calories of energy from whole foods.
Since RS is incompletely digested, we only extract about 2 calories of energy per gram (versus about
4 calories per gram from other starches). That means 100 grams of resistant starch is actually only
worth 200 calories, while 100 grams of other starch gives us 400 calories.
The way we’ve modified/processed grains and starchy vegetables in the modern food supply
diminishes the amount of RS we consume (think: cereal bars instead of oats, burgers instead of beans,
potato chips instead of boiled potatoes). Fibre sources such as wheat bran, psyllium, and methylcellulose (Citrucel) don’t have the same benefits.
Thus, to get the most benefits from RS, we need to consume it in whole food format.
Most developed countries (including Europe, the United States, New Zealand, and Australia), which
have a highly processed diet, consume about 3-9 grams of RS per day. In developing countries, diets
are often based around whole plant foods and the intake of RS tends to be around 30-40 grams per
day.
Where is RS found?
RS is found in starchy plant foods such as:
beans/legumes
starchy fruits and vegetables (such as bananas)
whole grains
some types of cooked then cooled foods (such as potatoes and rice)
The longer and hotter a starch is cooked, the less RS it tends to have.
In summary, we absorb more energy (calories) from cooked and highly refined and processed
carbohydrate dense foods. If we let machines and ovens do the digestion for us, we are left with highly
digestible starches. Not good for glucose control, staying lean, or intestinal health.
Various cultures thrive and stay lean when eating whole unprocessed legumes, intact grains and
starchy vegetables. RS may be one factor that enables this.
We might see some benefits from as little as 6-12 grams/day of RS, but closer to 20 grams/day might
be ideal. This is easy to get if you eat plenty of whole plant foods.
More than 40 grams/day might cause digestive problems — especially if this RS comes from
industrially produced RS products. In any case, we probably don’t get the same benefits of RS if it’s
processed (i.e. an industrially created RS product) as we do from whole foods.
SUGAR SUBSTITUTES
Sweet taste are also certain natural compounds belonging to the category of sugar alcohols such as
sorbitol (found naturally in some fruits), xylitol and maltitol.
These compounds, having a caloric value lower than that of fermentable sugars, are used in place of
sugar to achieve some common low-calorie products (foods and drinks "light" or "sugar-free") and in
order to prevent caries.
Also various other compounds, artificially produced and with a strong sweetening power (30 to 500
times that of sugar), are used to sweeten light foods and drinks, since, at the used doses, are practically
devoid of caloric power (cyclamates, aspartame, acesulfame, saccharin).
It should be emphasized that the consumption of sugar substitutes, although of current use, it is not
indispensable, even in cases in which a low-calorie diet is followed for weight reduction.
In fact, the use of these sweeteners not allows to reduce the body weight if the total amount of calories
of the diet is not decreased and without an increasing of the physical activity.
Anyway, even if substantially harmless in the doses permitted by law, the sweeteners may have
restrictions on use, so the label must be carefully read for eventual contraindications.
Their use is not recommended until 3 years of age and during pregnancy and lactation. Particular
attention should be paid to children over the age of three years, to which any administration of
products containing sweeteners should be made with caution.
The polyalcohols sorbitol, mannitol, and xylitol are naturally produced by some plant species, such
as fruits and berries.
Commercially, these sweeteners are synthesized and not extracted from natural sources. All
polyalcohols are slowly and not fully absorbed by passive diffusion in the bowel. Therefore, an
excessive consumption (eg. greater than 50 g of sorbitol per day, greater than 20 g of mannitol per
day) may be the cause of diarrheal phenomena.
Sorbitol is the most common, naturally found, polyol that is higher in some types of fruit (apples and
pears). It is obtained for reduction of glucose and is produced on an industrial scale by hydrogenation
of this monosaccharide, using a catalyst. The sorbitol is usually used, in mixture with other
polyalcohols, for sweetening chewing gum and confectionery.
Intense sweeteners
They are sweeteners to high sweetening power.
The four intense sweeteners in current use in Italy are: acesulfame K, aspartame, cyclamate (acid
cyclamic acid and its salts of sodium and calcium) and saccharin (and its sodium, potassium and
calcium salts). Two other intense sweeteners are authorized in the EU countries but are not pretty
much used in Italy: the neohesperidine DC and thaumatin.
Intense sweeteners are present in so-called "Table-top sweeteners" (tablets, sachets, powder or drops)
that in most of "sugar-free", "light" or “diet“ products : chewing gum, candy, soft drinks, yogurt,
jams, etc. Their sweetness varies from 30 to 500 times that of sucrose.
Their calorific value is almost nil. Since you only need small amounts, replace sucrose with these
substances can significantly reduce the contribution calorie of food.
Actually, both the intense sweeteners that the polyols are often used in mixture. Since their sweet
taste becomes stronger (the sweetening power of the mixture is higher than the sum of the powers of
each sweetener components), the amount needed to replace a teaspoon of sucrose is often lower than
that reported in the table.
PROTEINS
Functional and structural characteristics of a cell or of a living organism are determined by its protein
content. Proteins are 14-18% of the total body mass of an adult individual. They have “support”
function and enter into the composition of skin, muscles, tendons, nerves, and blood. Enzymes,
antibodies and many hormones are proteins. Chemically, they are large molecules (polymers)
consisting of simpler compounds (monomers), called amino acids. Proteins contain four basic
elements, carbon, hydrogen, oxygen and nitrogen. Their molecular weight ranges from 1,000 to
1,000,000 amu (atomic mass units) and their different organ function depends on the primary
structure, i.e. the sequence of the different amino acids, which are linked together by peptide bonds.
Amino acids are organic compounds, so called because they contain a carboxyl group (COOH), with
acidic properties, and an amino group (-NH2), having basic properties. Amino acids are quaternary
compounds, since formed by carbon (C), oxygen (O), hydrogen (H) and nitrogen (N).
In a peptide bond, two amino acids are linked together by expelling a water molecule, as follows:
H
|
H2N−C−CO- OH + H
|
R’
H
|
−ΝΗ−C−COOH
H
H
|
|
H2N −C− CO − NH − C −COOH
|
R"
|
R’
|
R"
The new bond between CO and NH is called peptide bond and the molecule resulting from the
combination of two amino acids is called dipeptide. Proteins are polypeptides.
There are twenty natural most common amino acids (Figure 1.7).
The amino acid sequence of a protein is its primary structure. The arrangement of individual
sections of the polypeptide chain indicates the secondary structure (α-helix, β-layer etc.); the global
configuration of the chain, tertiary structure and the relationships between these chains, the
quaternary structure. The synthesis of the proteins thus takes place for union of hundreds of amino
acid molecules.
While plants are able to synthesize the needed amino acids starting from simple inorganic substances,
animals are not able to carry out this synthesis as they does not fail to form the amino group (NH2),
hence the necessary to introduce the required amino acids for the protein synthesis with foods of plant
and animal origin. The human body can transform an amino acid, albeit limitedly, through the passage
of a NH2 group from a compound to another. By these metabolic conversions, our organism can
therefore also form amino acids starting from non-protein structures. Not all amino acids may be,
however, formed this way; the human body can not synthesize someone of them, called "essential",
and it is crucial (essential) that they should be introduced through a well balanced diet.
There are eight essential amino acids for adults and nine for child, which can not synthesize histidine.
Proteins that containing all eight essential amino acids that humans can not synthesize and therefore
must be included in the diet are called complete proteins (or high biological value proteins).
mg/g protein
essential amino acids
adults
boys
children
Histidine
0
0
14
Isoleucine
18
37
35
Leucine
25
56
80
Lysine
22
75
52
Metionine
24
34
29
Phenylanine
15
34
63
Threonine
13
44
44
Tryptophan
6.5
4.6
8.5
Valine
18
41
47
Daily requirement of essential amino acids.
The daily requirement of these compounds varies considerably in the child than in man. The human
body constantly renews its cellular elements, and its structural proteins. For protein synthesis is
essential that the necessary amino acids are present at the same time, hence the need for a balanced
protein diet. Cereal’s proteins, for example, lack of lysine and tryptophan, essential amino acids,
which are introduced with milk instead.
Proteins can be of animal or plant origin, and have different nutritional value. In general, proteins of
animal origin have higher biological value and are provided by foods such as meat, fish, eggs, milk,
cheese, etc. Protein of plant origin, of lower biological value, are found mainly in cereals and in
legumes. Eggs are the food with the highest protein content.
Proteins can be classified into two major groups:
• FIBROUS PROTEINS, insoluble in water, in most cases indigestible, constituting the essential
matter of animal tissues; such as: skin’s keratin, muscle myosin, fibrin of the blood;
• GLOBULAR PROTEINS, soluble in water, easily digestible, related to functions of maintenance
and regulation of vital processes; form all enzymes, many hormones including insulin, antibodies,
hemoglobin, and albumin egg.
In terms of nutrition, proteins serve a dual function:
a) energy production, since 1 g of proteins has a net calorific value of 4 kilocalories (the full
combustion of 1 g of protein develops 5.5 kcal but, unlike the other nutrients, for proteins there is a
loss of nitrogen compounds in urine and then the heat transferred to body is lower);
b) nitrogen providers for protein synthesis, in the form of essential amino acids. In this regard, the
biological nutrition’s value of a protein will be higher than more it will approach, as amino acid
content, to the organism’s needs. They include mainly animal proteins, because containing all the
essential amino acids; proteins from plants are incomplete and must be integrated.
In particular, enzymes are special proteins that make possible almost all of the chemical reactions
that are observed in human body and all the living organisms; for this reason, enzymes are also known
as biological catalysts or biocatalysts.
Function and protein metabolism
Our body is unable to produce either the amino group (NH2) or the essential amino acids; therefore,
proteins must be ingested in the diet in a balanced way.
The human body needs to constantly replace the “amino groups” (NH2), which have been converted
into urea (a component of urine, containing two amino groups), but the nitrogen excretion also occurs
peeling skin, hair loss, nail replacement and skin perspiration. A daily quantity of 0.25 g of protein
per kilogram of body weight would be sufficient, to compensate these losses but, generally, an adult
ingests 4-5 times as much, as the overall level of protein intake causes the body mass active and seems
be the regulatory factor of the level of overall activity and, hence, of energy expenditure.
12% of the average daily calories come from protein.
Since the requirement of essential amino acids is fixed and low, and the daily protein intake is far
higher than what it should be for a balanced diet, our body has at its disposal ever more essential
amino acids than it needs. According to this, the WHO has declared negligible for the man the
meaning of biological value for protein or "protein quality".
In fact, the diet in Western countries is increasingly rich in animal protein (up to 70% and above),
unlike that of the countries in the developing world, where animal proteins arrive at 5-10%.
The amino acids in excess (not used by the body) loose the NH2 group, and the non-nitrogenous
residues are then converted into carbohydrates or lipids.
In protein’s synthesis, the human body uses each amino acid derived from dietary proteins. From the
demolition of the tissue’s proteins, free amino acids are formed, which give rise to all the organic
proteins.
All our enzymes, antibodies, hemoglobin, and hormones are proteins. The blood’s antibodies form a
class of proteins known as immunoglobulins, whose quantity increases when the body is affected by
bacterial or viral diseases. A reserve of proteins does not exist in the human body, such as glycogen
for carbohydrates or adipose tissue for lipids, but the proteins of blood and tissues increase or
decrease, according to a more or less higher protein intake. There are different proteins: muscle
proteins have contractility; those of the hair, skin and nails exert a protective function and therefore
are tough and insoluble; those of the walls of blood vessels have elasticity, essential for the
maintenance of blood pressure. Those of bones and teeth, with specific minerals, have a structural
function; the plasma proteins exert an osmotic pressure which affects the movement of body fluids:
when the blood pressure exceeds the osmotic pressure, the liquid passes from the capillaries to the
cell interstices for a filtration process; when the ratio between the two pressures is reversed, the liquid
moves from the gaps to the capillaries for absorption. The osmotic pressure is directly proportional
to the concentration of plasma proteins: when this concentration decreases, there is an edema
formation, for the passage of large amounts of liquid from the capillaries to the interstices of organic
tissues.
The proteins are not absorbed as such, but after hydrolysis in amino acids, by proteolytic enzymes.
Their digestion, therefore, begins only in the stomach, for the competition of two agents contained in
the gastric juice, pepsin and hydrochloric acid. Pepsin is a specific enzyme for the digestion of
proteins; the cells of the stomach wall produce firstly an inactive molecule, pepsinogen, which
requires the presence of hydrochloric acid to be converted into pepsin. Pepsin cleaves peptide bonds
of proteins, transforming them into smaller molecules, peptones.
The absorption rates of individual amino acids are highly dependent on the protein source. For
example, the digestibility of many amino acids in humans, the difference between soy and milk
proteins and between individual milk proteins, beta-lactoglobulin and casein. For milk proteins, about
50% of the ingested protein is absorbed between the stomach and the middle part of small intestine,
and 90% is absorbed by the time the digested food reaches the ileum. Biological value (BV) is a
measure of the proportion of absorbed protein from a food, which becomes incorporated into the
proteins of the organism's body.
DETERMINING PROTEIN RECOMMENDATIONS IN DIET
Protein Quality
Measures of protein quality
Biological Value (BV)
Measures body retention of food protein
BV=100 => 100% of food protein retained
Protein Efficiency Ratio (PER)
Measures ability of protein to support growth
g growth/g protein fed
PER=3 => 3g growth per g or protein fed
The Biological Value (BV) takes into account the reused % of amino acids absorbed in order to
produce human proteins.
BV = (AAs used × 100) / AAs absorbed
For example: a protein introduced by food produces 950 AA during digestion. After their absorption,
only 585 AAs will become part of human proteins newly synthesized, the rest will have to be wasted.
What is the BV of the protein?
BV = (585/950) × 100 = 61.6
Protein digestibility-corrected AAs score
Protein Requirements
Current RDA for protein is 0.8 g/kg body weight per day
– ~65 g/day for a 180-lb (82-kg) individual
– ~47 g/day for a 130-lb (59-kg) individual
The RDA for protein is set to prevent deficiency (ie, maintain protein balance) in healthy
adults.
Does not consider potential benefits that might be obtained from amounts beyond RDA
– For example, the optimal protein intake for muscle function and athletic performance
(USDA National Agricultural Library Food and Nutrition Information Center. Available at:
http://fnic.nal.usda.gov/nal_display/index.php?info_center=4&tax_level=3&tax_subject=256&topic
_id=1342&level3_id=5140)
Protein Intake Recommendations
American College of Sports Medicine (ACSM) / American Dietetic Association (ADA)
– Endurance athletes, 1.2 to 1.4 g/kg per day
• Accounts for greater use of protein as fuel for energy
– Strength athletes, 1.2 to 1.7 g/kg per day
• To support muscle growth, particularly during early training phase when gains are greatest and
protein utilization is less efficient
Clinical studies suggest there is no apparent benefit at intakes above 2.0 g/kg per day
(American Dietetic Association, et al. Med Sci Sports Exerc. 2009;41(3):709-731. Tarnopolsky MA, et al. J
Appl Physiol. 1992;73(5):1986-1995).
Vegetarian Diets: Why become a vegetarian?
•
•
•
•
•
•
Health benefits
Environmental concerns about meat based diets
Animal welfare/ethical considerations
Economic reasons
World hunger issues
Religious beliefs
Vegetarian Diets: Potential Health Benefits
Obesity
% of obesity lower in vegetarian populations
Cardiovascular Disease
Risk of CHD 31% lower in vegetarian men and 20% lower in vegetarian women
Lower LDL-C, lower HDL-C
Hypertension
42% non-veg with hpt, 13% vegetarians
Also lower prevalence for
Diabetes
Cancer
Vegetarian Diets: Types
Non-red meat vegetarian
poultry, fish, dairy, eggs OK
Nutritional Benefits
Less fat, saturated fat, cholesterol
Nutritional Concerns
no special nutritional problems
May not be any better than typical US diet
may be high in fat, saturated fat, salt
cooking methods
junk foods, convenience foods
Lacto-ovo vegetarian
Milk & eggs OK
Nutritional Benefits
Like non-meat vegetarians
Nutritional Concerns
No special nutritional problems
May be high in fats, saturated fats
cheese & eggs
Strict Vegetarian: Vegan
no animal foods
Nutritional Benefits
Low fats, high fiber, plant-based
Nutritional Concerns
protein quality
probably OK, quantity may be an issue
calcium
no dairy, plant sources (leafy greens, soy), fortified foods (soy, rice milk)
iron
no meat, plant sources (leafy greens), cereals
vitamin B12
probably OK, cereals & supplements
Vegetarian Diet Planning
Protein is almost always adequate unless too much sugar and fat are used. Good sources include
beans, tempeh, tofu, quinoa and low fat dairy or soy milk products. TVP may be used occasionally
(Textured or texturized vegetable protein or TVP, also known as texture soy-protein or TSP, soy
meat, or soya chunks is a defatted soy flour product, a by-product of extracting soybean oil).
Vegans must use the equivalent of 1 1/2 cups of beans daily. Soaking them for 24 hrs and throwing
out the soaking water before cooking reduces gas formation.
VITAMINS
The National Institute of Health has reported that our body needs to consume 13 different vitamins
to maintain normal health. In this list of vitamins they include the vitamin B complex (folate, B12,
B6, biotin, pantothenic acid, niacin, riboflavin and thiamine) as well as vitamins K, E, D, C and A.
That is because each vitamin in the list is essential for different functions of the body.
Classification Standard
The main classification for vitamins is based on solubility, as some are soluble in water while others
are soluble in fat. The vitamins, which are soluble in fat, are stored by the body and therefore can
accumulate. On the other hand, the kidneys flush out water soluble vitamins. Another way that some
people classify vitamins is based on how they were obtained: either from food or naturally from food.
This method, however, can become complicated because many of the foods we consume on a daily
basis are vitamin fortified.
Fat-soluble Vitamins
Because the body stores fat-soluble vitamins in its cells, they are not flushed out as simply as the
water-soluble vitamins. This means that they do not require as frequent ingestion as water-soluble
vitamins but you still need sufficient amounts. It is important to remember that consuming too much
of fat-soluble vitamins can cause toxicity. We are particularly sensitive to high levels of vitamin D as
well as high levels of vitamin A specifically from animal sources. Simply consuming a balanced diet
should provide sufficient fat-soluble vitamins.
Vitamin Name
Function
Dietary Sources
Vitamin A
Vitamin A helps with healthy From retinol (animal sources): liver,
mucous membranes and skin, eggs, fortified margarine, butter, cream,
vision, tooth and bone growth cheese, fortified milk.
and the health of the immune From plant sources (beta-carotene):
system.
dark orange vegetables (pumpkin, sweet
potatoes, winter squash, carrots) and fruits
(cantaloupe, apricots); dark green leafy
vegetables.
Vitamin K is required for Vegetables from the cabbage family, leafy
Vitamin K
correct blood clotting.
green vegetables, milk; it is also produced
in the intestinal tract by the bacteria.
Vitamin E is an antioxidant Nuts and seeds, egg yolks, liver, whole-
Vitamin E
and helps protect the cell walls. grain products, wheat germ, leafy green
vegetables and polyunsaturated plant oils
(safflower, cottonseed, corn, soybean).
Vitamin D is stored in the Fortified margarine, fortified milk, fatty
Vitamin D
bones and is required to fish, liver, egg yolks; the skin can also
properly absorb calcium.
produce vitamin D when it is exposed to
sunlight.
Water-soluble Vitamins
Water-soluble vitamins are able to freely travel throughout the body and any unneeded quantities are
usually flushed out by the kidneys. Frequent small doses of water-soluble vitamins are required by
the body and this type of vitamin is not as likely to approach toxic levels as fat-soluble vitamins are.
In addition, vitamin C, choline, folate, vitamin B6 and niacin have higher consumption limits.
Consuming high levels of vitamin B6 during long periods of time can cause nerve damage that is
irreversible.
Most people are able to consume sufficient quantities simply by consuming a balanced diet. However
some vegetarians as well as those over 50 years of age may require supplements for sufficient B12
intake.
Vitamin Name
Ascorbic
(vitamin C)
Benefits
Dietary Sources
acid Ascorbic acid is an antioxidant Only found in vegetables and fruits,
and it is a portion of an enzyme especially: kiwifruit, mangoes, papayas,
that is required for protein lettuce,
potatoes,
tomatoes,
peppers,
metabolism. It also helps with strawberries, cantaloupe and vegetables
iron
absorption
and
is that are part of the cabbage family
important for the health of the
immune system.
Thiamine
Thiamine is a portion of an Found in moderate amounts in all of the
(vitamin B1)
enzyme that is required for nutritious foods: nuts and seeds, legumes,
energy metabolism and it is whole-grain/enriched cereals and breads,
important for nerve function.
pork
Riboflavin
Riboflavin is a portion of an Enriched, whole-grain cereals and breads,
(vitamin B2)
enzyme that is required for leafy green vegetables, milk products
energy metabolism. It is also
important for skin health and
normal vision.
Niacin
Niacin is a portion of an Peanut butter, vegetables (particularly
(vitamin B3)
enzyme that is required for leafy green vegetables, asparagus and
energy metabolism. It is also mushrooms), enriched or whole-grain
important for skin health as cereals and breads, fish, poultry and meat
well as the digestive and
nervous systems.
Pantothenic
Pantothenic acid is a portion of It is widespread in foods.
Acid
(vitamin an enzyme that is required for
B5)
energy metabolism
Pyridoxine
Pyridoxine is a portion of an Fruits, vegetables, poultry, fish, meat
(vitamin B6)
enzyme that is required for
protein metabolism. It also
helps with the production of
red blood cells.
Folic Acid
Folic acid is a portion of an Liver, orange juice, seeds, legumes, leafy
(vitamin B9)
enzyme that is required for green vegetables. It is now added to many
creating new cells (particularly refined grains.
red blood cells) and DNA.
Cobalamin
Cobalamin is a portion of an Milk, milk products, eggs, seafood, fish,
(vitamin B12)
enzyme
required
for
the poultry, meat. It is not present in plant
production of new cells and it foods.
is important to the function of
nerves.
Biotin is a portion of any It is widespread in foods and can be
Biotin
enzyme that is required for produced by bacteria in the intestinal tract.
energy metabolism.
MINERALS
The body needs many minerals; these are called essential minerals. Essential minerals are sometimes
divided up into major minerals (macrominerals) and trace minerals (microminerals). These two
groups of minerals are equally important, but trace minerals are needed in smaller amounts than major
minerals. The amounts needed in the body are not an indication of their importance.
A balanced diet usually provides all of the essential minerals. The two tables below list minerals,
what they do in the body (their functions), and their sources in food.
Macrominerals
Major minerals
Mineral
Function
Sodium
Needed for proper fluid balance, nerve Table salt, soy sauce; large amounts
transmission, and muscle contraction
Sources
in processed foods; small amounts in
milk,
breads,
vegetables,
unprocessed meats
and
Chloride
Needed for proper fluid balance, stomach Table salt, soy sauce; large amounts
acid
in processed foods; small amounts in
milk, meats, breads, and vegetables
Potassium
Needed for proper fluid balance, nerve Meats,
transmission, and muscle contraction
Calcium
milk,
fresh
fruits
and
vegetables, whole grains, legumes
Important for healthy bones and teeth; Milk and milk products; canned fish
helps
muscles
relax
and
contract; with
bones
(salmon,
sardines);
important in nerve functioning, blood fortified tofu and fortified soy milk;
clotting,
blood
pressure
regulation, greens (broccoli, mustard greens);
immune system health
legumes
Phosphorus Important for healthy bones and teeth; Meat, fish, poultry, eggs, milk,
found in every cell; part of the system that processed foods (including soda
maintains acid-base balance
pop)
Magnesium Found in bones; needed for making Nuts and seeds; legumes; leafy,
protein,
muscle
contraction,
nerve green
transmission, immune system health
vegetables;
chocolate;
artichokes;
seafood;
"hard"
drinking water
Sulfur
Found in protein molecules
Occurs in foods as part of protein:
meats, poultry, fish, eggs, milk,
legumes, nuts
Trace minerals (microminerals)
The body needs trace minerals in very small amounts. Note that iron is considered to be a trace
mineral, although the amount needed is somewhat more than for other microminerals.
Trace minerals
Mineral
Function
Sources
Iron
Part of a molecule (hemoglobin) found in red Organ meats; red meats; fish;
blood cells that carries oxygen in the body; poultry; shellfish (especially
needed for energy metabolism
clams); egg yolks; legumes;
dried fruits; dark, leafy greens;
iron-enriched
breads
and
cereals; and fortified cereals
Zinc
Part
of
many enzymes;
needed
for Meats, fish, poultry, leavened
making protein and genetic material; has a whole grains, vegetables
function in taste perception, wound healing,
normal fetal development, production of
sperm, normal growth and sexual maturation,
immune system health
Iodine
Found
in thyroid hormone,
regulate
growth,
which
development,
helps Seafood,
foods
grown
and iodine-rich soil, iodized salt,
metabolism
bread, dairy products
Selenium
Antioxidant
Meats, seafood, grains
Copper
Part of many enzymes; needed for iron Legumes,
metabolism
in
nuts
and
seeds,
whole grains, organ meats,
drinking water
Manganese
Part of many enzymes
Widespread
in
foods,
especially plant foods
Fluoride
Involved in formation of bones and teeth; Drinking
helps prevent tooth decay
fluoridated
water
or
(either
naturally
containing fluoride), fish, and
most teas
Chromium
Works closely with insulin to regulate blood Unrefined foods, especially
sugar (glucose) levels
liver, brewer's yeast, whole
grains, nuts, cheeses
Molybdenum Part of some enzymes
Legumes; breads and grains;
leafy
greens;
leafy,
green
vegetables; milk; liver
Other trace nutrients known to be essential in tiny amounts include nickel, silicon, vanadium, and
cobalt.
Recommended daily amounts (RDAs)
The recommended daily amount (RDA) refers to the EU guidance that is used for nutrition tables on
food products. There is no RDA for selenium and potassium.
Nutritional requirements are often slightly different for young children, adolescents, and during
pregnancy and breastfeeding.
CALCIUM
This mineral is essential for strong bones and teeth. It also plays an active role in the body's immune
system.
A lack of calcium in the diet is a contributing factor to osteoporosis, a condition that causes brittle
bones in adults.
High levels of calcium are found in dairy products such as milk and yoghurt. On average 250ml (half
a pint) of cows' milk or 150g yoghurt contains 300mg of calcium.
Some dairy products are high in fat, so you should meet your body's calcium needs by eating a diet
containing a balance of dairy and non-dairy foods.
Non-dairy food sources of calcium include: almonds, brazil nuts, hazelnuts, broccoli, curly kale, okra,
spinach, watercress, dried apricot and figs, mackerel, oysters, pilchards, salmon, sardines, pulses,
sesame seeds, tofu, calcium-enriched soya cheeses and milks.
The RDA for an adult is around 800mg.
IRON
Your body needs iron for healthy blood and muscles. It plays an essential role in the production of
the body's white blood cells and in the activities of the immune system.
Lack of iron causes anaemia and symptoms such as tiredness and irritability. Women lose iron when
they menstruate, and one in four British women do not get enough iron.
There are two types of iron in food:
haem iron found in meat and offal (essentially the iron from blood and muscle)
non-haem iron derived from some plants, grains and nuts.
Vegetable sources of iron also contain salts (oxalates and phytates) that affect how well the body can
absorb the iron. This means you need to eat a lot more to get the iron that your body requires.
Oily fish and egg yolks are quite rich in iron, but also contain substances that affect your body's ability
to absorb the iron.
The body can absorb:
20 to 40 per cent of the iron found in meat.
5 to 20 per cent of the iron found in vegetable sources.
How much iron the body can absorb also depends upon the presence of vitamin C and folic acid,
which improve your body's uptake of this mineral.
Sources of iron include: apricots, blackcurrants, figs, prunes, raisins, beans (including baked beans),
lentils, broccoli, curly kale, peas, savoy cabbage, spinach, watercress, eggs, lean red meat, poultry or
game, liver, kidney, liquorice, mackerel, oysters, sardines, tuna, nuts, wholegrain cereals and whole
meal bread.
The RDA for an adult is 14mg.
MAGNESIUM
Magnesium helps to regulate potassium and sodium levels within the body, which are involved in the
control of blood pressure.
It’s also used in the release of energy, for building strong bones, teeth and muscles, and regulating
body temperature.
Magnesium helps the body absorb and breakdown various other vitamins and minerals – for example
calcium and vitamin C.
Magnesium is found in lots of foods, and the following are good sources: apricots, bananas, figs,
prunes, raisins, brown rice, granary bread, wholemeal bread, wholewheat pasta, nuts, pulses,
courgettes, green leafy vegetables, okra, parsnips, peas, sweet corn, lean meat, milk, yoghurt.
The RDA for an adult is 375 mg. You should be able to get this amount from your daily diet.
ZINC
Zinc is an antioxidant and important for the maintenance of a healthy immune system.
It’s found in water, meat and cereal products so deficiency is rare.
A lack of zinc may be associated with skin problems, slow healing of wounds and low sexual libido.
Good sources include brown rice and wholegrain breads, cheese, crab, lobster, mussels, oysters,
sardines, duck, goose, kidney, lean red meat, turkey, venison.
The RDA for an adult is 10 mg.
SELENIUM
We need small but regular amounts of this nutrient for a healthy liver. It’s also one of the body's
antioxidants.
Selenium is found in soil, so the amount found in foods is dependent upon the farming methods used.
Over-cultivation of the land results in a depletion of its selenium levels, and a reduction in the
selenium content of the crop.
A diet that includes a combination of meat, fish and nuts will ensure an adequate intake of selenium.
Good sources include Brazil nuts, cashew nuts, cheese, eggs, milk, chicken, lean meat, liver, garlic,
onion, green vegetables, mackerel, salmon, tuna, sunflower seeds, whole-wheat bread.
POTASSIUM
Together with sodium, this mineral is active in the regulation of the body's water levels. Potassium is
also important in the transmission of nerve impulses, heart rhythm and muscle function.
It is found in most foods except oils, fats and sugars, but can be lost if food is overcooked.
Most fruit and vegetables contain potassium, with bananas, strawberries, fresh orange juice, apricots,
prunes, potatoes and green leafy vegetables providing the best sources.
Other sources include almonds, barley, brown rice, chick peas, corn, garlic, ginger, kidney beans and
tofu.
The Food Standards Agency (FSA) says adults need 2000 mg potassium a day.