Proteins

Proteins are the structural components of the body forming the basis of cells, tissues and organs. They are a large group of organic compounds consisting of carbon, hydrogen, nitrogen and oxygen atoms. Some contain sulphur and phosphorus also. When the proteins are digested they break down into smaller units called amino acids. Of the 20 basic amino acids 12 can be manufactured by the body and the rest,  called the 'essential amino acids' must be obtained from food. 

Proteins help to repair worn out or diseased tissues and to build new ones. It is used in the formulation of hormone, enzymes, red blood cells and antibodies. It also provides amino acids necessary for growth of fetus in pregnancy and for the production of milk proteins during lactation. Proteins are widely found in foods derived both from plant and animal sources.  Plant sources include beans, peas, pulses, whole grains, nuts and oil seeds; while red meat, poultry, fish, milk, cheese, yogurt and eggs are obtained from animals. Red meat is a good source of essential amino acids and iron and is traditionally regarded as 'first class' protein. But too much consumption of red meat may be harmful as it is a major source of undesirable saturated fat. One can eat more fish or chicken without the fatty skin instead of excess red meat. Vegetarians can obtain plenty of both from plant sources, whole grain cereals and from low fat diary products. A protein deficiency especially in infants and growing children can cause growth retardation, severe wasting of muscle etc.

The dietary requirements of protein depend on age and physiological state.  A part of the dietary protein is utilised or wasted to meet the energy requirements. So calorie intake should be adequate enough to meet the protein need or its maximum utilisation, taking into account the above factor.