Amino Acid Balance and Imbalance

Abstract

A protein lacking tryptophan (gelatin) or an amino acid mixture lacking threonine has been used to create amino acid imbalances involving tryptophan or threonine in diets containing casein supplemented with methionine. The magnitude of the growth depression caused by the addition of gelatin increased as the level of gelatin was increased. The magnitude of the growth depression caused by the amino acid mixture lacking threonine was greatest when the diet contained 6% of casein and was less if the level of casein in the diet was lower or higher. The magnitude of the growth depression caused by a constant amount of the amino acid mixture lacking threonine was shown to be related to the rate of growth supported by the original diet. However, the increase in the level of threonine required to prevent the growth depression appeared to be unaffected by the level of protein in the original diet.