What’s In Your Milk?: A1  Vs. A2 Beta-Casein & Disease Potentiation


In 1993, Professor Bob Elliot from Auckland University in New Zealand, was examining the incidence of Type 1 diabetes among Samoan children when he noticed that Samoan children living in New Zealand had a 10-fold increased risk of developing Type 1 diabetes compared to children living in Samoa. His suspicion was that this was related to either environmental or nutritional differences. He noticed similar patterns amongst children raised in certain African countries compared to those in Europe, Australia, New Zealand, and the United States and he started to look more closely at children’s diets.

Although much of Elliot’s original research was inconclusive and potentially biased, he found was something milk biochemists have known for a long time; that cows in these countries produced different milk proteins, namely A1 and A2 beta-casein. A1 beta-casein producing cows are found in western countries (Australia, New Zealand, Europe, and the United States), and A2 beta-casein producing cows are found in Iceland, some Asian and African countries including Samoa. Milk biochemists postulate that a genetic mutation occurred some 8,000 years ago involving an amino acid swap: proline at position 67 of the milk protein (what is now known as A2 milk) was replaced by histidine (what is now known as A1 milk). This genetic mutation persisted and is the dominant milk protein type in cattle herds throughout the western world.

Keith Woodford, a Professor of Farm Management and Agribusiness at Lincoln University in New Zealand published a book in 2009 titled, Devil in the Milk, wherein he expanded upon Bob Elliot’s work and took a critical look at the evidence published in more than 100 scientific papers on the topic.[1] These studies, primarily epidemiological, examined the link between consumption of A1 milk and the incidence of heart disease, Type 1 diabetes, and various neurological conditions. His hypothesis, which has since been investigated more closely through several randomized controlled trials, suggests a relationship to specific disease potentiation and the consumption of A1 milk.

Many scientists postulate that the issue with A1 milk stems from a tiny protein fragment known as bovine beta-casomorphin 7 (BCM7). BCM7 has opioid characteristics and a strong affinity for mu-opioid receptors which in the presence of a permeable digestive system (i.e. “leaky gut”), can easily pass from the gut to the circulatory system causing a deleterious health effect. An opioid is any chemical that resembles morphine or other opiates in its pharmacological effects. They act on the central and peripheral nervous system, as well as the gastrointestinal system. Babies naturally have permeable digestive systems within the first 12-months of life, and are therefore, particularly sensitive to BCM7 passing through to the circulatory system. Adults with conditions causing a “leaky gut” may also be susceptible to BCM7’s effects. The only enzyme that breaks down BCM7 is dipeptidyl peptidase 4 (DPP4). Low DPP4 may be another risk factor for BCM7 having a systemic effect. DPP4 may be low due to genetics or certain medications, namely diabetic medications.

Results from a randomized controlled study published in The European Journal of Nutrition in 2014, supported the hypothesis that BCM7 creates an inflammatory response present in various health disorders.[2] The conditions receiving the most research attention for the potential relationship to A1 consumption are Type 1 diabetes, heart disease, food intolerances, allergies, delayed psychomotor development, SIDs, and autism. A 2017 systematic review investigated the specific gastrointestinal impact of A1 vs A2 beta-casein and confirmed that there is an inflammatory correlation with A1 consumption in human health however, the mechanism by which this occurs is not yet clear.[3]

Today there is a whole line of A2 milk being sold throughout stores in Australia and New Zealand. Many people who previously thought they were lactose intolerant have found A2 milk to be tolerable. This may be because it wasn’t the lactose that they were sensitive to, but rather the milk protein, namely breakdown products of A1 beta-casein. Many with milk-related allergy conditions, such as eczema and asthma, are finding these conditions subside when switching milk consumption from A1 to A2 milk types.

Although there are some people in the United States milk industry advocating for A2 milk, they are few and far between. There is an option however, for those interested in testing out the proposed relationship between A1 milk and various health conditions. Goat and sheep’s milk are A2-like with proline at the 67th position. Just some geeky milk science to keep in mind next time you shop the cheese counter. May be worth a try, or at least an interesting topic of conversation at your next naturopathic doctor’s appointment.

Do you have chronic digestive problems, food allergies, intolerances, or any condition that you think may be aggravated by your diet? A healthy functioning digestive system can set you up for optimal nutritional absorption and immune status, and is not something to be left out of your overall health plan. Would you like to find out more about what may be contributing to these problems and what can be done about it? Naturopathic doctors are trained to focus on gastrointestinal health as a major component of overall health. Seek the care of a trusted ND who can help you explore all elements of your health in a comprehensive manner to help you discover ways that you can become the healthiest possible version of you.

  1. Woodford, Keith. Devil in the Milk: Illness, Health and the Politics of A1 and A2 Milk. Chelsea Green Publishing, 2009.

  2. Ho, Suleen, et al. "Comparative effects of A1 versus A2 beta-casein on gastrointestinal measures: a blinded randomised cross-over pilot study." European journal of clinical nutrition68.9 (2014): 994.

  3. Brooke-Taylor, Simon, et al. "Systematic Review of the Gastrointestinal Effects of A1 Compared with A2 β-Casein." Advances in Nutrition 8.5 (2017): 739-748.