Orally administered peptides are assumed to be degraded into amino acids in the body. However, our recent studies revealed some food-derived prolyl and pyroglutamyl peptides with 2-3 amino acid residues in the blood of humans and animals, while most of the peptides in the endoproteinase digest of food protein are degraded by exopeptidase. Some food-derived dipeptides in the body display in vitro and in vivo biological activities. These facts indicate that the biological activities of food-derived peptides in the body rather than those in food are crucial to understanding the mechanism of the beneficial effects of orally administered peptides.
Keywords: bioactive peptide; bioavailability; food; functional food; peptide.