Use of a Peptide Rather Than Free Amino Acid Nitrogen Source in Chemically Defined “Elemental” Diets

Previous studies have shown that amino acid (AA) residues are absorbed more rapidly from di- and tripeptides than from free AA. In the present study, an intestinal perfusion technique has been used in normal human subjects to compare absorption of AA residues and total α-amino nitrogen (N) from 4 partial enzymic hydrolysates of protein (50–80% of the N contents present as small peptides) and their respective equimolar free AA mixtures. α-Amino N absorption was greater from 2 casein hydrolytes and a lactalbumin hydrolysate than from the respective free AA mixtures but similar to that from a fish protein hydrolysate and its AA mixture. The considerable variation in absorption of individual AA residues from the AA mixtures was much reduced when the protein hydrolysates were perfused, as a number of AA which were poorly absorbed from the AA mixtures were absorbed to a greater extent from the protein hydrolysates. The casein and lactalbumin hydrolysates had a stimulatory effect on jejunal absorption of water a...