the smallest quantity of protein in food necessary for the maintenance of nitrogen balance in the body. A decrease of protein in food below the minimum protein requirement leads to a deterioration of the body’s own proteins. The minimum protein requirement depends on the individual characteristics of the body, age, nutritional state, and also on the quality and quantity of the nonprotein components of food (carbohydrates, fats, vitamins, and so on). The amount of protein necessary for man or animal varies with the biological value of food proteins, which is determined by their content of various amino acids. Many proteins and protein mixtures are not complete because they lack certain amino acids that cannot be synthesized in the bodies of men and animals. The establishment of nutritional rations requires orientation toward the optimum protein requirement—that is, the quantity of protein necessary for complete provision of the body’s needs. For an adult person, this averages 80–100 g of protein; with hard physical labor, 150 g.