Beta-casein comprises 30% of the protein content in cows’ milk and regular milk contains both A1 and A2 beta-casein. These have different outcomes upon digestion when compared to one another due to a slight difference in the amino acid sequence on the peptide chain. Recent studies indicate that A1 beta-casein preferentially releases the opioid peptide beta-casomorphin 7 (BCM-7) on digestion. In contrast, the structure of A2 minimizes or limits the release of BCM-7 on digestion. (Asledottir, et al. 2017, 2018)
An infographic providing an overview of the A1 and A2 beta-casein protein variants. The graphic displays how upon regular milk consumption, BCM-7 is released resulting in gastrointestinal differences.