The biological value of proteins

Abstract

, using young growing rats as experimental animals, found that the biological value of proteins was lessened as the proportion of the protein in the diet was increased. He considered that this result might in part be due to the fact that proteins could be used more economically for maintenance than for growth. When supplied in the diet in a low proportion, almost all the protein would be used for maintenance, whilst, as the level was increased, an increasing proportion would be used for growth. Martin and Robison [1922], working on themselves, found that the value of wheat proteins for the maintenance of nitrogenous equilibrium remained steady when these were present in the diet at different levels; the values they obtained for milk proteins, on the other hand, were most irregular. Boas-Fixsen and Jackson [1932], using adult male rats as experimental animals, found that the biological value of maize protein was increased when its level in the diet was lowered, but Boas-Fixsen [1930] found no progressive change in the nutritive value of a sample of dry-heated, purified caseinogen when the amount present in the diet was raised from 5 to 15 %, the