Food is the chief of essential materials which the body needs
for its well-being.These essential materials are called 'nutrients'.
Good food is indespensable for health at all stages of life and for
satisfactory growth during infancy,childhood,adolescence and
adulthood.Wholesome food in adequate quantities is no less important
for pregnant and nursing women since they undergo a severe
nutritional stress.
The nutrients found in foodstuffs may broadly be classified as
1.Carbohydrates
2.Fact
3.Proteins
4.Minerals
5.Vitamins
6.Water.
Proteins,fats and carbohydrates are called Macro Nutrients.
Proteins :
Proteins (from the Greek word proteios meaning first)
are the most versatile elements in the body.They are the
chief substances of the cells of the body. They form important
constituents of muscles and other tissues and vital fluids like
blood.Enzymes,which assist in the digestion of food,and anti-bodies
which are the body defences against infections are also mainly
protein in nature.
The nutritive value of protein depends on the essential amino acid
composition. Amino acids are the bricks with which tissue protein
is built and replaced.There are some 20 amino acids commonly found
in dietary proteins. Of these,10 amino acids can be synthesised
by the body itself, whether by mutual conversion among amino acid
or from non protein sources.But 10 amino acids cannot be so
synthesised and have to be supplied through diet.These are called
essential amino acids. Adults require 8 essential amino acids
while children require 9 to 10.
Fat :
Fact,like proteins,is a necesssary ingredient in diet and is
of value to the body in a number of ways.It is a concentrated
source of energy and supplies per unit weight more than double
the energy furnished by either protien or carbohydrates. Some
fats,especially vegetable oil,provide what are called essential
fatty acid,linoleic and arachidonic acid, to the body.
Fats that circulate in the blood are of many types-
triglycerides,phospholipids,etc.The quantity and quality
of fat consumed affects the level of cholesterol in the blood.
Some fats groundnut oil,sesame oil sunflower oil which contain
a high proportion of polyunsaturated fatty acids do not increase
blood cholesterol level greatly. Others like butter,ghee and
hydrogenated vegetable oils (vanaspati) contain high proportions
of saturated fatty acid and greatly increase cholesterol levels.
It is also found that consumption of smaller amounts of fat at
different times causes less increase of cholesterol than a large
amount of fat taken at a time.
Carbohydrates :
Carbohydrates include every kind of starch and sugar.Grainfoods are
largely composed of starch and foodstuffs like cane sugar and glucose
are pure carbohydrtes. They form the main source of energy for the
body.Being a cheap source of energy,carbohydrates form the bulk of
indian diet. A balanced diet simply means a diet that will supply
all the nutrients necessary for the growth and development of the
body.
Vitamins and Minerals :
Vitamins and minerals comprise micro nutrients as distinguished
from proteins,fats,and carbohydrated-called macro nutrients.
vitamins can be broadly divided into fat-soluble and water-soluble
vitamins.Vitamin A,D,E and K are fat-soluble vitamins.Vitamin
C and B are water-soluble.
A large number of minerals are present in the body and perform
a variety of functions.Minerals account for about 4% of the body
weight.Calcium and phosporus form about three-fourths of the
mineral element.Five other minerals-potassium,sulphur,sodium,
chlorine and magnesium-account for most of the rest.Many elements
are present in such minute quantities that they are called trace
element or micro-nutrients.
