Occurrence, biological properties and potential effects on human health of β-casomorphin 7: Current knowledge and concerns

The genetic variant A1 of bovine beta-casein (beta-Cn) presents a His residue at a position 67 of the mature protein. This feature makes the Ile(66)-His(67) bond more vulnerable to enzymatic cleavage, determining the release of the peptide beta-Cn f(60-66), named beta-casomorphin 7 (BCM7). BCM7 is an opioid-agonist for mu receptors, and it has been hypothesized to be involved in the development of different non-transmissible diseases in humans. In the last decade, studies have provided additional results on the potential health impact of beta-Cn A1 and BCM7. These studies, here reviewed, highlighted a relation between the consumption of beta-Cn A1 (and its derivative BCM7) and the increase of inflammatory response as well as discomfort at the gastrointestinal level. Conversely, the role of BCM7 and the effects of ingestion of beta-Cn A1 on the onset or worsening of other non-transmissible diseases as caused or favored by still need proof of evidence. Overall, the reviewed literature demonstrates that the beta-Cn A1/BCM7 issue remains an intriguing but not exhaustively explained topic in human nutrition. On this basis, policies in favor of breeding for beta-Cn variants not releasing BCM7 and consumption of A1-like milk appear not yet sound for a healthier and safer nutrition.