Dietary proteins are involved in the synthesis of tissue protein and other special metabolic functions. In anabolic processes they furnish the amino acids required to build and maintain body tissues. As an energy source, proteins are equivalent to carbohydrates in providing 4 calories per gram. Proteins perform a major structural role in all body tissues and in the formation of enzymes, hormones and various body fluids and secretions. Proteins participate in the transport of some lipids, vitamins and minerals and help maintain the body's homeostasis.
Proteins consist of nitrogen, oxygen, carbon and hydrogen.