Studies on Amino Acids in Self-Selected Diets

Abstract

Ten essential amino acids were determined microbiologically in the self-selected diets of 4 women. Determinations were made both on a composite sample and on separate groups of foods. The total intake of amino acids always appeared to be greater when determined on separate foods than on composites. The greatest discrepancies were found with lysine, methionine and tryptophan, with intermediate losses observed for histidine, threonine, phenylalanine and arginine. Values for leucine, isoleucine and valine were similar whether made on the separate foods or on the composites. Satisfactory recoveries of bound and free amino acids were found in all cases in the presence of high-protein foods but in the presence of carbohydrate-rich foods the losses ranged as indicated above. The amounts of most of the essential amino acids consumed by the subjects were significantly higher than the levels recommended by Rose. Methionine, however, appeared to be limiting. Negative nitrogen balance seemed to be related to total protein intake, and also to the distribution of protein in meals throughout the day.