American Journal of Clinical Nutrition, Vol 27, 130-135, Copyright © 1974 by The American Society for Clinical Nutrition, Inc.

Reassessment of amino acid requirements of young women on low nitrogen diets. III. Isoleucine, threonine, phenylalanine, and summation

¹ From the Departments of Nutrition and Home Economics, Rutgers University, New Brunswick, New Jersey 08903

Young college women served as experimental subjects in a series of eight experiments in which N balance was studied on different levels of isoleucine, threonine, phenylalanine, and, finally, on a mixture of essential amino acids representing the estimated requirements from these investigations. The experimental diet provided 5 g N/subject per day and, except for the evaluation of the total estimated requirements, levels of amino acids representing twice the highest estimate determined by earlier workers. Under these conditions the requirements for the three amino acids investigated were lower than previously reported. In two studies the mixture of the estimated requirement levels of the essential amino acids maintained all subjects in adequate N equilibrium, and twice the estimated requirement levels were no better than the estimate. In a third experiment, carried out during a college examination period, the estimated requirements were inadequate in maintaining N balance. Three subjects in this experiment had previously been supported in positive N balance on the same diet when no such stress situation prevailed. It was concluded that the essential amino acid requirement of adult women is a relative and not an absolute one, and may vary with level and pattern of N and amino acid intake; it is also influenced by other conditions as exemplified by the stress engendered by college examinations.