Effect of Amino Acid Imbalance on Dietary Choice in the Rat

Abstract

A study was undertaken in an effort to determine more precisely the influence of the severity of an amino acid imbalanced diet and the importance of the quantity of the limiting amino acid on the choice of the rats for or against the imbalanced diets. When rats were allowed to choose between an imbalanced diet (which would support a slow rate of growth) and a protein-free diet (which would not support growth), they selected the latter almost exclusively. They also selected the imbalanced diet supplemented with the most-limiting amino acid over the imbalanced diet. Rats offered a choice between a protein-free diet and one of a series of imbalanced diets containing increasing increments of the amino acid mixture lacking threonine (from 1% to 5.4%) showed a decreasing preference for the imbalanced diet and an increasing preference for the protein-free diet as the quantity of amino acid mixture in the imbalanced diet was increased. When increasing levels of threonine (from 0.05% to 0.45%) were added to the imbalanced diet, the rats showed a gradually decreasing preference for the protein-free diet. Rats pre-fed a high protein diet consumed greater quantities of the imbalanced diet than those prefed diets with lower concentration of protein.