Proteins are the main solid matter in the muscles; they are also the major constituents of blood, matrix of bones, teeth, skin, nails and hair. The body constitutes 60% water and 19% fat and is held together by only 17% proteins and 4% minerals. In fact, every living cell and all body fluids except bile and urine contain protein. The principia functions of proteins are as follows:
1. Body building or building of new tissues:
Proteins are the chief substance in the cells of the body. They supply the building materials for the body and make good, the wear and tear of tissues which is a constant feature of the process of life and it is for this reason that foods rich in protein are often called ‘body building foods’.
2. Regulations of body processes:
Body proteins have highly specialized functions in the regulation of body processes. For example, hemoglobin, an iron bearing protein that is the chief constituent of red blood cells performs a vital role in carrying oxygen to the tissues. The plasma protein is of fundamental importance in the regulation of Osmotic pressure and in the maintenance of water balance. The body’s resistance to disease is maintained in part of antibodies which are protein in nature. Some enzymes and hormones like insulin and thyroid are protein in nature. Amino acids also have specific functions in metabolism.
3. Milk Formation:
Mother’s milk contains 1.2% protein, and the first and best food for any young infant. The milk proteins are synthesized in the mammary glands from the available dietary and tissue proteins. Therefore, a nursing mother needs to take extra protein in her diet to meet the demands of protein for milk formation.
4. Energy Supply:
Proteins are a potential source of energy and each gram of protein yields 4 kilocalories of energy. Generally, proteins are expensive food. So carbohydrate foods should preferably be used for energy and proteins spared for performing their specific task of building and repairing body tissues. The excess of protein is converted into fat and stored in the body.