Proteins are one of the basic and essential nutrients consumed by man. Both animal and vegetable sources provide proteins in the human diet. Many proteins derived from animal sources are nutritionally adequate because all essential amino acids are present. However, proteins from vegetable sources are often deficient in one or more essential amino acids. Therefore, vegetable protein must generally be supplemented with other proteins in order to provide good nutition. However, vegetable proteins can provide a satisfactory diet if the individual is judicious in selecting foods.
A study of 1955 data indicated that approximately 55 percent of the protein component of the American diet came from animal sources. A recent analysis indicated that red meats contributed approximately 30 percent of the animal source to total protein. Dairy products, poultry, and fish contributed the balance. Similarly, wheat flour provided approximately 15 percent of total vegetable protein intake with other cereals (rice, corn, barley and rye), legume seeds (beans, peas and soybeans), and nuts constituting the balance.