Influence of Amino Acid Deficiencies and Protein Level on the Plasma Cholesterol of the Chick

Abstract

Deficiencies in the amino acids arginine, lysine, methionine and tryptophan were studied at different levels of protein intake in relationship to growth rate and plasma cholesterol of the young chick. It was shown that at suboptimal protein intakes, a hypercholesteremia resulted which could be modified by supplementing the deficient protein with amino acids such that more protein would become available to the bird. At optimal or supernormal protein intakes arginine, when added to a casein diet deficient in this amino acid, continued to extert a cholesterol-lowering effect which could be explained on the basis of greater protein availability; lysine and tryptophan, when added to proteins deficient in these amino acids, exerted no effect on the plasma cholesterol level and methionine produced a cholesterol-lowering effect which was not related to any improvement in protein quality or growth rate. Although the feeding of cholesterol increased the hypercholesteremia of birds on low-protein diets, essentially normal levels of plasma cholesterol were observed when the protein deficiency was alleviated.