Assessment of Nutritional Status of Men: Protein

Abstract

Eight healthy young men were used as experimental subjects in a study to learn whether a deficiency of tryptophan, lysine, or methionine affects the constituents of urine and blood plasma. A simple method by which an early deficiency of protein or of any essential amino acids might be detected was evaluated. Nitrogen balance generally became negative after deprivation of any of the essential amino acids. After a short-term deficiency, as in the present experiment, excretion of creatinine remained constant and the excretion of urea and 17-ketosteroids varied in a normal range. On day 8 of tryptophan deprivation the excretion of N-MNA decreased, and that of pyridone decreased in 2 subjects and increased in one subject. In the deprivation of lysine or methionine, there was no significant trend of change. The concentration of plasma amino nitrogen remained normal. The plasma aminogram did not show any specific pattern that could be related to a deficiency of protein or of an essential amino acid. However, the free amino acid ratio in plasma increased significantly during the deficiency period, and this might be of value in detecting subclinical levels of protein deficiency.