The Case of the Curious Caseins – A1/A2 Milk

It is always exciting to encounter a fresh topic that has escaped attention, yet with a little investigation, demands it.  So it is with the story of A1 / A2 milk.  I first became aware of the existence of this issue at a potluck dinner with health-conscious fellow diners.  As it turns out, this is old news to residents of New Zealand, where a few researchers and entrepreneurs have been promoting the virtues of A2 milk for about a decade.  The story is about the role of a milk protein, beta-casein, that can take on two very similar forms, called A1 and A2, depending upon a single simple mutation of one gene.  The A1 form of the beta-casein, upon digestion, breaks down into beta-casomorphin-7 (BCM7), a fairly stable and strong opiate which appears to cause health problems in some people some of the time.  Meanwhile, the A2 beta casein proteins are digested completely and don’t generate the problematic BCM7.

The evidence suggests that BCM7 can trigger the auto-immune response responsible for Type 1 diabetes, and it is implicated in arterial damage and consequently could be a factor in heart disease.  In addition, there is evidence for connections between BCM7 and autism, schizophrenia, sudden infant death syndrome (SIDS) and milk intolerance.

The story is well-told  by Keith Woodford in his book, Devil in the Milk: Illness, Health and the Politics of A1 and A2 Milk.  The author has a nice synopsis of the major scientific findings on his website.  I find the evidence and the arguments he presents for the case against A1 milk quite compelling.  But what makes this story particularly interesting, and the book fascinating reading, are the personalities that have shaped policy surrounding the science and the agriculture, and the all-too-predictable response of large organizations against making any kind of change.

The solution to the A1 milk problem is easy.  Just stop breeding dairy cows using bulls with A1 genes, and in a few cow generations the milk will have a lot less A1 beta casein in it.  The cost for such an adjustment is minimal.  Many of the dairy bulls used for artificial insemination have already been genetically tested and their A1/A2 status is known.  The cost of genetic A1/A2 testing is only a few dollars per head; nothing compared to the cost of raising breeding stock.

But we live in a world where brand is everything.  Any hint that milk might not be the most wholesome of foods just cannot be allowed to reach the public.  In New Zealand, where this issue first became known, the large milk marketing company Fonterra was always ready to downplay and counter any scientific findings that hit the public media.  The milk companies and government regulators have been content to let reasonable scientific skepticism serve as an excuse for doing nothing, and presently this is the state of affairs.

Let’s look at just a bit of the evidence for the A2 milk hypothesis, just to give readers a glimpse of the argument and potential health consequences.  We will look at the results from a study by Murray Laugesen and Robert Elliott, published in Journal of the New Zealand Medical Association in 2003.  The graph below shows the death rate from ischemic heart disease as a function of A1 beta-casein consumption for several countries that all have established health care systems.  The trend is obvious and is highly unlikely to be due to chance.

The authors look at other correlations, such as total milk protein, butter fat, or other dietary differences, but nothing has as strong a correlation as A1 beta-casein consumption.  The study also looked at the correlation of A1 beta-casein consumption with the incidence of Type 1 diabetes, and here the correlation was even stronger.

If you take the study numbers at face value, and assume that, in the US, the milk supply could become free of A1 beta-casein, then you might expect a reduction of about 40 deaths per 100,000 annually due to heart disease, just extrapolating from the linear correlation coefficient in the chart above.  This would amount to about 60,000 fewer deaths from heart disease every year.  (For perspective, auto accidents kill about half that number.)

Scientific “proof” that there is a problem with A1 beta casein is a standard that will not be reached until long-term double-blind studies are done on humans – which could be decades in the future, if ever.  The cost of such studies could easily be more than the cost of just solving the problem! That the solution is so simple with such low costs, the down-side risks virtually nonexistent, and the potential public health benefits so large, make this issue a fascinating case study in the politics of indecision.

The best solution would be for some industry group or public entity to promote or require farmers in a defined geographic area to begin the switch to only A2 milk-producing cows.  In the matter of a few years, with good record-keeping and now with a significant sample size, the change in A1 beta-casein content in the milk supply should show up in a change in the incidence of Type 1 diabetes and heart disease statistics.

Individually, the risks from milk are not high, just as riding in a car is not particularly dangerous.  However, if the driver is drunk, or the body is prone to other compromises, even individual risks can become significant.  In the US, the only source of milk that does not contain A1 beta-casein is goat milk, or milk from cows that are known to be genetically A2A2 homozygous individuals — difficult if not impossible to find.  In other parts of the world, A2 milk is becoming more available.

I suspect that someday there will be no more A1 beta casein allowed in milk, but that time is a long time away.  In the mean time, don’t expect our health watch-dogs to protect you any better than they did from cigarette smoking.


  1. A fine review Gary. The hope I see is for a small farm that controls it’s own herd to reduce A1 beta casein, then use that as a marketing tool. A successful campaign could educate the public and encourage others to follow suite, and eventually move the industrial organic distributors. Of course, rapid success brings it’s own challenges for smaller players.

    I’ll forward your post to Stephanie Gibson, General Manager at Lochmead Farms. Seems like a good fit locally.

  2. Your review of this “controversy” is the most balanced I’ve read so far. Bravo.

    There is obviously a genetic component here. I only drink raw milk from an organic Amish farm. It’s all A1. Zero negative symptoms. In fact quite the opposite. Since I started drinking it over 5 years ago my IBS is a faded memory. My immune system has never been better. It amazes me that with so much genetic diversity along with the science of epigenetics (whether a gene is turned on or off) someone could broadly demonize a particular variety of food (a1) as bad for everyone 100% of the time. It would too expensive and impractical to apply any form of scientific methodology to such a large number of variables involved. Which is why we are left with nothing more than speculation and zero hard facts. There will likely never be the obvious reasons stated above.

  3. Further more…

    A1 vs A2 Response from Organic Pastures

    Mark McAfee wrote several years ago (
    For all of the A-2 followers out there….

    The A-2 Corp, years ago courted OPDC and OPDC said “no”. The A-2

    Corp required all raw milk that they tested and sold to be pasteurized

    under their brand. Their ideas were so good and made so much

    difference that they went bankrupt in North America.

    A-2 pasteurized milk caused all sorts of allergies and serious lactose

    intolerance just like any CAFO processed milk anywhere. Dr. Tom

    Cowan even told me that he was sorry for writing “the forward to the

    book” before he knew what he knows now.

    The problem with A-2 followers is that they do not think for themselves

    and believe everything they read “hook line and sinker”….they just

    follow unconfirmed, unverified writings done by two guys ( now dead )

    from New Zealand. If A1 ( or Mixed A-2 and A1 milk like OPDC raw

    milk… cause we can not get tested and do not know what we have

    exactly ) was so bad then why does grass fed raw organic milk do all

    the same great things that A-2 is supposed to do???

    Mike schmidt is absolutely right…and I say that:

    “The Devil is not in the Milk”….”The Devil is in the Feed, Conditions and

    the Processing!!!”.

    Click to access A-2%20OPDC%20position.pdf

    The jury is still out for sure….they will not be back either. The court was

    adjourned because there is no evidence or science. This has all the

    signs of a New Zealand scam.

    1. Hi JMills,
      Thanks for your comment. Interesting take from the OPDC. You won’t hear an argument from me about the desirability of local pastured milk. I’d rather not get into the issue about raw versus pasteurized milk. There may be health effects in either direction, especially when considered as a public health issue. However, I certainly think that individuals should be able to weight those risks and make the choices they deem best. When I had a cow, I certainly enjoyed the raw milk!

      But on to the A1/A2 controversy. I remain convinced that Keith Woodward was telling an evolving story as honestly as he could, and that it will continue to develop. I just stopped by his website since you got me thinking about this issue again to see if anything else has happened on this issue, and sure enough, there is another study…
      I’m still betting that in a hundred years all of our cows will be producing A2 milk.

  4. In the proteins found in milk, a protein called beta-casein makes up 30%. Beta-casein is of two kinds: A1 Beta-casein and A2 Beta-casein.

    Regular milk which has A1 protein causes many digestive issues when A1 milk is consumed, BCM-7 is produced. BCM-7 can cause intolerance symptoms and indigestion.

    Whereas the structure of A2 is closer to the human milk beta-casein chain, it doesn’t produce BCM-7. This is why milk containing only A2 naturally supports digestive well-being. It’s naturally more digestible than A1 milk. A2 milk has shown to have medicinal benefits. It is particularly essential during pregnancy and childhood.

    Regular milk mostly contains A1 protein which may cause uneasiness and according to some studies, can increase the risk of many diseases.

    A2 protein milk is gentle on sensitive tummies and less likely to trigger symptoms associated with milk intolerance. Research shows that A1 protein milk causes many digestive issues. Moreover, A2 milk is high in Omega 3 & 6, Vitamins, Calcium, Minerals, Iodine, Magnesium, antioxidant Beta-Carotene and many more.

    Research shows that milk from desi Gir cows with a different kind of protein called A2 is not only nutritious but also easier to digest.

    Amlaan A2 milk originates from cow’s milk and is healthy for all age groups and contributes to a high protein diet providing you cow milk nutrition.

    Read more:

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