American Journal of Clinical Nutrition, Vol 16, 229-231, Copyright © 1965 by The American Society for Clinical Nutrition, Inc.

Further Observations on the Amino Acid Requirements of Older Men

II. Methionine and Lysine

¹ From the Veterans Administration Center and the Departments of Medicine and Biological Chemistry, School of Medicine and the School of Public Health, University of California, Los Angeles, California

Six men aged fifty-eight to seventy-three years were fed purified amino acid mixtures containing variable amounts of methionine in diets containing less than 50 mg. of cystine and with a total nitrogen intake of 7 gm. per day. One subject required 2.4 gm. of methionine per day to maintain nitrogen balance; one required 2.7 gm. and two required 3.0 gm.; the remaining subjects required more than 2.1 gm. but their exact requirements were not determined.

Four men aged fifty-three to sixty-four years were fed diets of purified amino acid mixtures containing variable amounts of lysine. Two subjects were in nitrogen balance with 1.4 gm. of lysine per day; however, there were two subjects over sixty years of age who were not in balance on this amount but achieved nitrogen equilibrium when the quantity of lysine in their diet was increased to 2.8 gm.

These results constitute evidence that under the experimental conditions reported herein the amounts of methionine and lysine needed to maintain nitrogen balance appear to be greater in older men (between fifty and seventy years of age) than in younger men.