Bioavailability of bioactive peptides derived from food proteins across the intestinal epithelial membrane: A review

Bioactive peptides (BAPs) play a crucial physiological role in human health. To exert their biological effects after oral administration, BAPs have to be transported across the human intestinal barrier into the blood circulation system, and must reach their targets in an intact or active form. However, few reviews have summarized current understanding of BAP transport to exhibit activities (bioavailability) and its knowledge gaps. To obtain a better insight into BAP absorption and aid the design of improved functional foods for humans, this review summarizes and discusses the mechanistic transport pathways, modulatory factors, human studies, solutions to improve the bioavailability, and future perspectives of BAPs. Both passive (paracellular and passive transcellular diffusion) and active (transporter and transcytosis) routes are possible involved in the BAP transport process, which can be influenced by various properties of peptides, including hydrophobicity, charge, size, molecular weight, amino acid sequence, stability, and enzymatic degradation. Peptidase-resistant BAPs can be transported into the bloodstream at concentrations in the micromolar range and remain intact for several minutes to hours to excise bioactivities. Studies of the effects of BAPs in humans are required, and the bioavailability of BAPs will be at the forefront of future functional food research.