Introduction to Nutrition
Nutrition are substances, which provide energy to the human body and include carbohydrates, proteins, fats and lipids, minerals, vitamins, eggs, water etc.
Food is the main source of the body fuels.
The ingested food undergoes metabolism to give energy required for the vital activities of the
body.
Details included as;
CARBOHYDRATES
One gram of carbohydrates gives 4.6 Kilo calories (4600 calories).
Carbohydrates rich foods are potatoes,
cane sugar, cereals, fruits, sweets, syrups,
chocolates and beet roots.
Glucose can be produced in the body from amino acids and glycerol Carbohydrates
and fats are protein sparer i.e. they are used first, as the source of energy, instead of proteins hence prevent protein loss.
Protein sparing action of carbohydrates is
greater than that of fats.
Some intermediate products of carbohydrate metabolism provide amino acids e.g.
pyruvic acid and oxaloacetic acid can be
aminated to form alanine and aspartic acid
respectively.
Diet rich in sucrose may promote dental
caries.
In certain metabolic conditions plasma level of lipids increases in response to carbohydrate rich diet e.g. type-IV hyperlipidemia or endogenous hypertriglyceridemia.
(gluconeogenesis).
PROTEINS
lg of proteins produces 4.2 kilocalories
(4200 calories).
In growing children, growth is dependent
on proteins. Proteins are required to pro-
vide amino acids (building blocks) for the
synthesis of other body proteins necessary
for growth.
In adults, proteins are required to main-
tain the optimum level of amino acids
to synthesize new proteins after wasting
illness and to furnish the protein loss by
wear and tear.
Proteins supply amino acids,which
required to form enzymes, proteinous hormones, antibodies and different
non-proteinous nitrogenous substances
like purines, pyrimidines, coenzymes etc.
proteins derived from animals contain all the essential amino acids and therefore are called first class proteins or the proteins of high biological value.
Plant proteins do not contain all the
essential amino acids and therefore are called second class proteins or the proteins of low biological value.
Proteins that are taken from animal sources are better in quality than those derived from
plants.
The nutritional value of any protein
depends upon the nature of its amino acids
and their concentration.
Higher the biological value (net protein
utilization) of a protein, higher will be its
nutritive value.
Animal proteins are well digested and ab-
sorbed than plant proteins.
Plant proteins can be made first class pro-
tein by mixing together two kinds of plant
proteins so that, the essential amino acids
absent in one protein can be supplied by
other protein.
Individuals who are engaged in strengthous physical work need relatively more proteins.
FATS AND LIPIDS
1g of fats produces 9.1 Kilocalories (9100
calories)
Fats have highest caloric value.
They also transport fat-soluble vitamins
and fatty acids.
Fats reduce the bulk of food and add taste
to it.
They have a high satiety value thus they
can relieve hunger for a longer period.
Fatty acids, which are not synthesized in
the body and must be taken in food, are
known as essential fatty acids.
• Essential fatty acids are polyunsaturated.
Vegetable fats have more polyunsaturated
fatty acids than animal fats.
• Essential fatty acids are important component of mitochondrial and cell membranes phospholipids.
Essential fatty acids are found in high concentration in reproductive glands.
Essential fatty acids help in the transport of cholesterol. They also lowers
the cholesterol level thus protect against
atherosclerosis.
Arachidonic acid (essential fatty acid) is a
precursor of prostaglandins.
Deficiency of these fatty acids affects both,
the infants and the adults. Symptoms
include dry, scaly and thickened skin and arrested growth.
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