Amino Acid Balance and Imbalance: XII. Effect of Amino Acid Imbalance on Self-Selection of Diet by the Rat

Abstract

Observations of some effects of an amino acid imbalance on food intake and food selection of rats in different physiological states are described. The imbalance was created by adding a mixture of amino acids lacking histidine to a purified diet containing 6% of beef fibrin. Food intake was depressed when the diet in which there was an imbalance of amino acids was substituted for one containing balanced protein; and rats given a choice between the “imbalanced” diet and a protein-free diet showed a decided preference for the latter over the former. This preference became evident more quickly with nondepleted and with starved rats than had previously been observed with protein-depleted rats. Neither protein-depleted nor non-depleted rats showed a specific preference for either of 2 balanced diets which differed in nutritive value, but both groups showed a clear preference for a more balanced diet over an imbalanced diet when the 2 diets differed by only 0.05 to 0.1% of L-histidine·HCl.