Comparison of oral feeding of peptide and amino acid meals to normal human subjects

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Abstract
Intestinal perfusion studies performed in man have suggested that amino acid N may be absorbed more rapidly from peptides than free amino acids. The effects of the oral administration of peptides and free amino acids were compared. Two isonitrogenous liquid test meals, 1 containing 50 g of a partial enzymic hydrolysate of fish protein in which .apprx. 80% of the N content was present as small peptides (peptide meal), and the other a mixture of free amino acids (amino acid meal) the composition and molar pattern of which simulated that of the peptide meal, were administered on separate occasions to 6 normal subjects intubated with a triple lumen tube. Both meals contained the reference marker polyethylene glycol. Fractional absorption of amino acid residues 1 and 2 h after ingestion of the 2 meals was similar at 3 intestinal locations situated 120, 160 and 200 cm from the mouth of each subject, and at 2 h 73.8% and 72.0% of the amino acid residues were absorbed, respectively, by the time the contents of the peptide and amino acid meals reached the middle sampling port of the tube. The total sum of individual amino acid increments in plasma was significantly greater 30 min (P < 0.025) and 1 h (P < 0.05) after ingestion of the peptide than amino acid meals. By 3 h the total area under the 2 plasma curves was similar. Normal human subjects appeared to be capable of assimilating orally administered mixtures of peptides and free amino acids with equal efficiency. Secretion of fluid into the lumen of the upper small intestine, assessed by reference to dilution of the polyethylene glycol, was less after ingestion of the peptide meal. In clinical situations characterized by fluid and electrolyte malabsorption consideration might be given to using small peptides rather than free amino acids as the N source in nutritional diets.