A1 beta-casein from normal cow’s dairy can be inflammatory, but only in people with the enzyme that cleaves it to the inflammatory peptide beta-casomorphin-7 (BCM7).
A2 casein from goat, sheep, and A2 cow dairy is usually fine.
Not all cows produce A1 beta-casein. It comes from Holstein and Friesian cows who are the dominant breeds in western Europe, North America, and Australia. Dairy cows in Africa, Asia, Iceland and southern Europe make milk with mostly A2 casein. Those countries have a lower incidence of the conditions discussed below.
Milk that has predominantly or exclusively A2 casein is fine for most people. I find this in my clinic again and again. Goat’s milk is A2. And so is milk from Jersey cows. Dairy products that are mostly fat (such as butter) are also fine.
Conditions affected by A1 casein and dairy products
A1 beta-casein is potentially a trigger for Type 1 diabetes. It is also highly implicated in coronary artery disease and autoimmune disease.
A1 beta-casein may also play a role in autism and schizophrenia. In fact, casomorphin is more damaging to the brain than the gliadorphin from gluten. Casomorphin’s drug-like effect explains why it worsens anxiety and mood disorders and causes cravings for dairy and sugar.
The inflammation from A1 beta-casein can cause lymphatic congestion, metabolic suppression, and weight gain. It can also worsen acne, eczema, upper respiratory infections, asthma, and allergies.
Finally, A1 beta-casein can stimulate mast cells in the gut and cause digestive problems and lactose intolerance. A2 milk is usually fine.
I have made the clinical observation that A1 casein can drive or worsen endometriosis, and believe it does so because of its inflammatory, immune-disrupting effect.
Some people are fine with dairy
Some people are fine with A1 beta-casein because they do not have the enzyme that forms beta-casomorphin-7 (BCM7). There is no blood test and it is not an allergy. Instead, you just have to try avoiding A1 dairy and see how you feel.
A clinical sign that can suggest a problem with A1 casein is a history of childhood recurrent upper respiratory infections.
Further reading:
- What dairy does to periods
- Professor Keith Woodford’s book Devil in the Milk: Illness, Health, and the Politics of A1 and A2 Milk
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- 2014 peer-reviewed animal study in the European Journal of Nutrition: Comparative evaluation of cow β-casein variants (A1/A2) consumption on Th2-mediated inflammatory response in mouse gut. (Evidence that A1 beta-casein (but not A2 casein) generates inflammatory markers including myeloperoxidase (MPO) and interleukin-4 (IL-4).)
- 2014 human study: Comparative effects of A1 versus A2 beta-casein on gastrointestinal measures: a blinded randomised cross-over pilot study.
- 2015 study: Epigenetic effects of casein-derived opioid peptides in SH-SY5Y human neuroblastoma cells.
- 2016 study: Clinical evaluation of glutathione concentrations after consumption of milk containing different subtypes of β-casein: results from a randomized, cross-over clinical trial.
- 2017 study: “Strikingly different pattern” of digestive symptoms in people identified as lactose intolerant after drinking A2 Milk compared to conventional milk.