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.