The Optimum Form of Dietary Nitrogen in Gastrointestinal Disease: Proteins, Peptides or Amino Acids?

At one time it was thought that proteins had to be hydrolysed to free amino acids before absorption but this hypothesis was finally overturned in the 1960’s and it is now clear that peptide absorption in the gastrointestinal tract is of major nutritional significance. The products of luminal hydrolysis (free amino acids and small peptides) can be absorbed either as free amino acids—by four group specific amino acid transport systems, or as intact di— and tripeptides—by a separate transport system. Tetra— and higher peptides require brush border hydrolysis and the products are absorbed either as free amino acids or as di— and tripeptides.