Prediction of plasma amino acid concentration from diet amino acid content.

The level of each plasma amino acid in male weanling rats was examined in relation to their intake from gluten, casein, synthetic amino acid, or zein diets. Plasma levels of valine, leucine, and isoleucine were found to be linearly related to the intake per gram diet regardless of the dietary source. Although levels of most other amino acids were not linearly related to intake, they were predictable if both the concentration of the amino acid in the diet and chronic level of protein intake were known. That is, a relationship, which applied to all diets, was found between the concentration of amino acid in the plasma, the concentration in the diet, and the total protein or amino acid nitrogen in the diet.