What to do with A2?

December 5th, 2009 by jeff

A Review of the A2 Milk controversy for Dexter Owners

Jeffrey L Newswanger DO

Here at Hope Refuge Farm, we recently acquired a very nice polled, red bull from the Belle Fourche farm.  The seller informed us that, in addition to his other great traits, he is homozygous for A2. At first, this information meant nothing to me. However, when I learned that A2 referred to characteristics of the milk his off-spring might produce, I was immediately interested.   Our breeding goal at Hope Refuge is to develop Dexters suitable to be family milk cows.  As a primary-care physician and small scale farmer, I am very interested in the relationship between health and agricultural.   Thus, I began a thorough review of the scientific literature in a quest to understand the mystery of A2 milk. The literature trail that I discovered proved at various times to be intriguing, confusing and occasionally downright disgusting.

Milk contains dozens of proteins. These are divided into two groups based on their function. The first, whey proteins, are small, water soluble and are closely associated with the liquid portion of the milk.  The second group is the caseins. These larger proteins are the main constituent of “milk solids.” Caseins can be divided into alpha caseins and beta caseins.  Beta caseins are further divided into type A1 and A2.  So when we speak of A2 milk, we are talking about the type of beta casein that is predominant in the milk.  This is determined by the genetics of the cow producing the milk. Researchers suspect that A2 beta-casein is the original form or “wild-type” beta-casein. Sometime, long ago a mutation took place that caused a cow to produce A1 beta-casein.  Over time her descendants have become very numerous.  In the common commercial herds of Europe and America, A1 beta-casein is the predominant type. Asian and African cows generally produce A2 milk exclusively.  Interestingly, the channel island breeds such as Guernsey and Jersey tend to produce A2 beta-casein predominantly also.

The current controversy began in New Zealand. The significance of A2 beta casein was initially suggested in 1992 by RB Elliott who observed that the incidence of diabetes among children in Polynesia was much lower than that of Polynesian children living in New Zealand. The main difference between these two groups was that Polynesians who remained in the islands prolonged breast feeding where as those in the more developed New Zealand changed to cow milk based formulas.  This observation led to a series of animal trials attempting to figure out what component of cow milk might be responsible for triggering the development of diabetes.  Eventually, in 1997, Elliott and his team published results of a trial in which genetically susceptible mice fed A1 beta casein where found to be more likely to develop diabetes than those fed A2 beta casein.  More studies were done in mouse, rat and rabbit models resulting in a growing body of literature suggesting that A1 beta casein might increase the risk of both diabetes and arteriosclerosis (the underlying cause of heart attacks and strokes). Other researchers compared rates of human diabetes and heart disease in nations where the milk tends to be high in A1 with nations in which the milk tends to be high in A2.  This effort resulted in a serious of studies demonstrating higher rates of heart disease and diabetes in the nations where people consume the most A1 beta casein.

Now, it must be noted that these studies had serious limitations in design.  There are many other differences between nations than the type of milk produced. Also, the rodents used in the animal trials have a metabolism somewhat different from humans.  However, the striking fact is that the bulk of these studies all seem to point in a similar direction.   The few published papers that suggest there is no difference between A1 and A2 milk are from obscure journals and contain little new scientific data.

So, if the bulk of the data points in one direction, why is there still so much controversy? Unfortunately, the answer lies in politics and financial interest. In 1994, a method for determining which beta casein a cow produces was patented in New Zealand.  Soon after, the A2 Corporation was founded with the goal of creating herds of cattle that had been screened to produce only A2 beta casein.  The A2 Corporation proceeded with an aggressive and successful marketing campaign.  The A2 milk health fad grew in New Zealand and then spread to Australia and the Western United States, all under the carefully managed control of the A2 Corporation. While the A2 Corporation was funding studies confirming the dangers of A1 milk and the benefit of A2, Fonterra, the world’s largest dairy marketer, funded its own studies which demonstrated just the opposite.   And so, the exploration of this potentially important finding has run amok in a bog of financially-biased studies and public relations spin-doctors.

So, where does this leave us?  First of all, we do not yet have a firm answer as to the significance of A1 versus A2 milk.  Part of the reason is that more research is still needed.  Unfortunately, the infighting and money politics have impeded the ability to get these studies done.  However, another part of the reason is that the kind of experiment that would prove once and for all whether A1 is dangerous and whether A2 is beneficial would have to be done on humans and would be unethically dangerous to the people involved.  For this reason, we will probably never have the sort of proof that some are demanding.  As time goes by, the picture should become clearer.  For now, however, it is my professional opinion that there is enough data to raise concern.  I do not think everyone should stop drinking milk.  Even if the A1 is actually harmful, there are many other nutritional benefits to milk. However, if it is practical to get milk without A1 beta casein (ie: A2 milk) then there is a very good chance that this would be better for you.

This brings us back to Dexters.  Unscientific data I have obtained by conversation with other Dexter owners suggests that, although only a few have been tested, those Dexters tested have been predominately A2 positive.  We, as an association, need to know whether Dexters produce A1 beta casein.  If we can test a significant number of animals and demonstrate very high rates of the A2 gene in the population, then Dexter milk may have benefit over that of other breeds.  We must be careful not to get carried away with making claims that are unsubstantiated.  The jury is still out on A2 milk.  We do not want to hurt the reputation of the breed or the association by rash and premature statements.  However, I think it would be valuable if we could begin to understand the genetics of our breed awhile.  This information may become extremely valuable if A2 milk is proven superior to “ordinary” milk.  Unfortunately, the test to determine whether a Dexter carries the A2 trait is no longer available.  It is my hope that the Dexter associations will work to make this test available again.

For further reading:

To those interested in learning more, I would recommend Devil in the Milk by Keith Woodford. (Chelsea Green Publishing, 2007)  Although Professor Woodford is an unapologetic proponent of A2 milk, he gives an honest accounting of the data so far on this topic. He also provides good information on the genetics of cattle breeding for A2.

9 Responses to “What to do with A2?”

  1. Sandy Gunder Says:

    Hi Jeffrey

    I’m not sure when you posted this information, but thank you. My family (and granddaughters) are now using a2 milk exclusively as it does not cause the stomach pains, sky high temperatures and chest infections that came after ingesting even a small amount of a1 milk. My husband was actually tested for Qfever and leptospirosis at one stage because of the demonstrated symptoms following drinking a1 milk.

    We have an interest in Dexters, as we see ourselves eventually retiring to a small holding in New South Wales in the next couple of years, and would like a milking cow that is a2 proven.

    I’ll be keeping a keen eye out to see what the further tests show.

    Kind regards
    Sandy Gunder
    Sydney, Australia

  2. David Cluff Says:


    Good news! The Legacy Dexter Cattle Registry currently offers the A2 milk DNA test for $25.00. Legacy is not a breed association, but a genetic data base. You can visit their website http://legacydextercattleregistry.com for more information and testing options.


  3. Callie Says:

    I am just starting to research A2 milk and Dexters. My jersey just tested A1/A1…alas. Thanks for this article. It encourages me to continue to look at Dexters as a replacement for my current cow. Davis University in Ca does the testing in the USA.

  4. kim Says:

    Good to hear from you, Callie. As soon as I found out Davis was doing the A2 test, I sent in samples on all my cows. Two of my Dexters are A2/A2, one is A1/A2, and our Dexter/Jersey cross is A1/A2.

  5. Gene Bowen Says:

    Thanks for the post about A2 milk. It’s a well written, well thought out piece.

  6. Judy Sponaugle Says:

    Exellent article on A2 milk. Legacy was instrumental in bringing A2 testing to America and we are encouraging breeders to submit their A2 test results to be compiled and published on the web. This will help other breeders to determine “obligate” status for lines that have been tested. If some breeders are reluctant to publish A1 or A1/A2 animals that is helpful but not required as the A2/A2 animals are those best used for determining obligate status. Lines with A1 bred to A2 animals still need to be tested for status.

  7. Patti Adams Says:

    We have tested 15 animals in our Dexter herd for Beta Casein. Approximately 40% are homozygous for A2 Beta Casein. Our current herdsire has also tested as homozygous for A2 Beta Casein, so we are routinely producing heifers and bull calves that are homozygous for A2 Beta Casein. All of our Kerry herd is homozygous for A2 Beta Casein. It’s not hard to find a milk cow that is homozygous for A2 Beta Casein. So what’s the big deal?

    If a breeder tests for Beta Casein at UC-Davis, their test report is available and considered as “Intellectual Property” of the A2 Milk Corporation. Say what??? Yeah, the test that you pay for, actually belongs to the A2 Milk Corporation. They “own” it, and they have certain rights, because they own it and they have patents and trademarks in regards to “A2 Milk”. Read the fine print.

    Are we willing to allow a foreign corporation (New Zealand based) to control how we use our test results?? Apparently we are, because if we test our cattle for A2 Beta Casein through UC-Davis (or “Legacy”), we give away these rights to the A2 Milk Corporation. It may not be such a “great deal”.

  8. Judy Sponaugle Says:

    For the record; ALL laboratories in the US that test for A2 milk sign an agreement to test within the patent rights of the A2 Corp, although until it became public an ADCA supported lab was circumventing the A2 company patent and testing without license. Nothing has changed regarding the patent rights or license or reporting to A2 corp. The lab cream always rises to the top.

  9. Kim Says:

    Yes, Judy, you’re correct. Any A2 test done at any lab is the intellectual property of A2 Corp. And all the fine print really says is that you’re not allowed to use that information with the intent to form an exclusively A2 herd or to produce A2 milk. I don’t think that’s giving away my rights.

    But I DO think it means that there are a lot of Dexter folks out there who better be careful about all the clamoring to get all A2 cows.