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Consumption of A2 protein milk has some functional advantages in comparison to A1 protein milk

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The main protein in cow’s milk is casein (~80% of protein in milk). Casein exists in solution in a structure called micelles which are composed of several forms of casein. One of the main forms is beta casein, which itself can be found in two main variants in cow populations, A1 and A2 beta casein. Originally, most cows would have had the a2 genotype (wild type), like human milk. As a result of selective breeding to produce higher yielding cows, a SNP (a single change in the genetic code) resulted in a mutation in the A2 beta casein gene becoming fixed within herds. This mutation yielded a variant in the beta casein genes protein product called a1 protein. Over time this A1 gene has become the dominant gene in the most commercially important cow breeds, meaning that today most dairy herds and by extension most dairy products contain predominantly A1 protein.

The human body digests A1 protein differently than A2. Digestion of A1 protein in vivo (in humans and animals) yields a peptide molecule capable of interacting with opioid receptors in the gut, being absorbed into the blood stream and capable of crossing the blood brain barrier. This opioid molecule is called a casomorphin, and more specifically a betacasomorphin or BCM-7 (because it is 7 amino acids in length).

As the name suggests betacasomorphins are opioid molecules. The opioid system and associated signalling pathways, feedback mechanisms and physiological cascades are highly conserved across mammalian species where it plays a diverse array of roles and interplays with a host of other important physiological systems. Its influence in human health, specifically its impact on the nervous and hormonal system, early life development, lactation, reaction to environmental stimuli, mother and child bonding etc. is hugely important topic in medicine and science and still the subject of a significant research and development.

Consumption of A2 has some functional advantages in comparison to a1 which are directly related to the impact of BMC7 on human physiology. These functional properties are well established through an extensive body of research compiled over the last several decades and includes extensive cell based, animal studies, human studies, clinical trials and multiple reviews and metanalysis. We detail these advantages in the evidence base section of our website.

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