Studies of Protein Absorption Using Nitrogen15 as a Tag

Abstract

Methods for the study of protein absorption in man have been discussed. A yeast protein tag with an N¹⁵ content of 58.3 atom % excess was prepared. Evidence for the general distribution of the tag throughout the protein fraction of the yeast has been reviewed. Comparative absorption studies in young and old subjects have been presented. A mean yeast protein absorption of 90.3% among 6 subjects has been determined. Achlorhydria, hypochlorhydria, and age do not appear to produce depressing effects on the capacity to absorb a protein tracer during continued high-level protein intake. The role of gastric acidity in protein utilization will be further discussed in a subsequent communication. The single-dose tracer method of determining protein absorption has been shown to obviate the need for evaluation of endogenous nitrogen.