The Effect of Sources of Nonessential Nitrogen on Nitrogen Balance in Young Adults

Abstract

Four young adult subjects were maintained on an experimental diet wherein the amount of whole egg was adjusted to supply near-minimal amounts of the essential amino acids. Supplemental nitrogen provided from 60 to 80% of the total dietary nitrogen and was varied as to source. When a nonessential amino acid mixture replaced glycine at a total nitrogen intake of 6.5 gm, there was an average increase in nitrogen retention of 0.71 gm per day per subject. When the nonessential amino acid mixture replaced a mixture of glycine and DAC at a total nitrogen intake of 10 gm there was an average increase in nitrogen retention of 0.15 gm per day per subject. A comparison of nitrogen balance when the nonessential amino acid mixture was fed at the two levels of nitrogen intake shows that increasing the amount of nonessential amino acids resulted in an average decrease in nitrogen retention of 0.17 gm per day per subject. These results were taken as evidence that, under the experimental conditions, glycine alone as a source of supplemental nitrogen is not as well utilized as a mixture of nonessential amino acids nor as an ammonium salt and glycine mixture when this mixture is fed at a higher nitrogen level. The combination of ammonium salt and glycine appeared to be as effective as a mixture of the nonessential amino acids in maintaining nitrogen equilibrium.