Proteins build and repair body tissue, play major roles in regulating various body functions, and provide energy if there is insufficient carbohydrate and fat in the diet.
The primary function of proteins is to build and repair body tissues. This is made possible by the provision of the correct type and number of amino acids in the diet. Also, as cells are broken down during metabolism (catabolism), some amino acids released into the blood are recycled to build new and repair other tissue (anabolism). The body uses the recycled amino acids as efficiently as those obtained from the diet.
Proteins are important components of hormones and enzymes that are essen-tial for the regulation of metabolism and digestion. Proteins help maintain fluid and electrolyte balances in the body and thus prevent edema (abnormal reten-tion of body fluids). Proteins also are essential for the development of antibodies and, consequently, for a healthy immune system.
Proteins can provide energy if and when the supply of carbohydrates and fats in the diet is insufficient. Each gram of protein provides 4 calories. This is not a good use of proteins, however. In general, they are more expensive than carbohydrates, and most of the complete proteins also contain saturated fats and cholesterol.