Nitrogen balances for young adult males fed two sources of nonessential nitrogen at two levels of total nitrogen intake

Six young male adults were fed constant intakes of purified essential amino acids and of total nitrogen(N), 4 Gm. Although glycine is a nonessential amino acid (NEAA), in this study it was fed always with diammonium citrate and not with the mixture of 7 NEAA. In 1 period 53 per cent of dietary N was provided by NEAA and the mean N balance was −0.14 Gm. per day. In another period 53 per cent of dietary N was provided by glycine + diammonium citrate, and mean N balance was −0.02 Gm. per day. The results indicated no difference in N balances for the 2 sources of nonessential nitrogen, when 4.0 Gm. N are fed. Following adjustment to a 10 Gm. N intake, the same subjects were given a constant intake of purified essential amino acids and 3 variations in source of nonessential N. When 1.2 per cent of dietary N was furnished by NEAA, the mean N retention was 0.35 Gm. per day. When 0.6 per cent of N intake was provided by NEAA, the mean N retention was 0.66 Gm. per day. When the only nonessential amino acids ingested were those of the basal diet, mean N retention was 0.56 Gm. per day. Although retentions were higher in the absence of purified NEAA and when 0.6 per cent of dietary N was furnished by NEAA than when 1.2 per cent of the N intake was provided by NEAA, differences between means were not statistically significant at the 1 per cent level.