Understanding the Science Behind A2 Milk

Some of you may have heard about a new kind of milk making its way to the U.S., starting in California. No, it’s not the latest entry into the milk alternatives aisle of your supermarket to sit alongside soy, rice or almond beverages, but rather an alternative type of cow’s milk that comes from a unique type of cow. Known as “A2 milk,” this type of milk looks and tastes exactly like the milk that is probably in your refrigerator right now. Is it any different than regular milk? At this point, there is only preliminary science to support that it has benefits above and beyond the nutrition and health benefits of the cow’s milk products already available.

What exactly is A2 milk? First, a little background. There are a number of different proteins in milk. You may have heard of whey or casein, the two main types of milk proteins. One protein in particular is called beta casein and there are two common forms: A1 and A2. Most milks contain a mix of both A1 and A2 beta casein. The milk in your refrigerator right now likely has pretty close to a 50/50 distribution of A1 and A2 beta casein, although the proportion of A1 and A2 beta casein in milk can vary with different cow breeds. According to the makers of A2 milk, it contains A2 beta casein, but not A1 beta casein.

What does this all mean? Well, in the 1990s A2 milk was first touted as a healthier alternative to regular milk. It was proposed that regular milk may be implicated in type 1 diabetes and heart disease risk, and that A2 milk would not be associated with these same risks. But the research on this was unsubstantiated because the implications for regular milk could not be confirmed according to a scientific review published in 2005 and another in 2011. In fact, a research study showed that traditional milk consumption may be linked to a reduced risk for cardiovascular disease, but more data is needed.

The makers of A2 milk promote its potential health benefits; however, the science to support benefits beyond those of tradition milk is limited. More recently, the makers of A2 milk have proposed that the benefit lies instead in how A2 milk is digested, and they suggest that the A1 casein in regular milk is responsible for the digestive discomfort that some experience when drinking milk.

Is there strong science to support this claim? Again, the science is limited. There are only two studies in people, the first of which was published in 2014. What did that study find? There was mostly no difference observed between regular milk and A2 milk in digestive symptoms, with the exception of higher stool consistency (i.e., softer stool) while drinking regular milk.

There were also no differences between the two milks in the blood test for inflammation used as an indicator of digestive dysfunction. The study authors did report that a subset of the participants experienced much higher inflammation values when consuming regular milk, but there was another subset of participants that experienced higher inflammation after consuming A2 milk. Thus, there needs to be more research to evidence the potential benefit of A2 milk based on this one study in people. And the authors agree that there is a need for further study to determine if there are additional benefits of consuming A2 milk.

The second human study, published in 2016, appeared to do little to advance the first study. While the authors report a similar distinction between the physiological and symptomatic effect of consuming A1 and A2-containing milk and A2 only-containing milk, this study has several limitations. Participants were a mix of perceived and actual lactose intolerant individuals, making interpretation of results difficult. Additionally, the vast amount of comparisons between experimental and control conditions leave open the strong possibility of false positives. For example, there were a total of 60 experimental vs. control comparisons for the measurements of digestive symptoms, only 10 of which were significant in favor of A2. Thus, more research is needed to support this study.

So, while it may be an interesting scientific theory, the A2 milk concept today remains a theory until there is more science to support it. Based on the current science, there is not sufficient scientific support for the proposed mechanisms and beneficial health effects of A2 milk versus regular milk. Based on the shared overall nutritional profile of A2 and regular milk, A2 milk provides the same health benefits that are provided by traditional milk. So, whatever milk your patients or clients choose, they can be confident in its nutrition and health benefits.