Nitrogen utilization from elemental diets.

Repletion experiments were performed in malnourished, chair-adapted primates to explore recently reported differences in nitrogen utilization from elemental diets. Two elemental diets were fed consecutively for 8 days through a gastrostomy. Diet C (maltodextrins, peptides, crystalline amino acids) resulted in: larger weight gain (F1,6 = 17.93, p less than 0.01); smaller decrease of serum albumin (F1,5 = 11.2, p less than 0.015), larger increase in total iron binding capacity (F1,6 = 30.6, p less than 0.002), and a more positive nitrogen balance (F1,6 = 30.4, p less than 0.002) than diet V (glucose oligosaccharides, crystalline amino acids). Diet C was considered to be more effective in the nutritional repletion of the study animals. Additional experiments were performed in normal human volunteers to investigate the metabolic fate of ingested glutamine and whether the rapid catabolism and excretion of the amido nitrogen of this amino acid, which constitutes 11.56% of total nitrogen in diet V, could explain the differences observed in primates in our study and in human subjects by other authors. Six normal volunteers were fed 15N amino glutamine, 15N alanine, or 15N H4Cl. Similar amounts of 15N from Gln and Ala were excreted in 10 hr. The amido group of glutamine does not seem to be metabolized differently from the alpha-amino group of alanine under the conditions of the study. The marked differences in nitrogen utilization from the study diets could not be explained by the presence of relatively large amounts of glutamine in one of them.