Should You Drink A2 Milk?


US, February 06, 2019: FIRST, THERE WAS SOY milk. Then almond milk. Then cashew, coconut and oat milks crowded supermarket fridges. And now, there’s an increasingly visible milk to wrap your head around: A2 milk, which is marketed as “easier on digestion.” But what exactly is this product – and are the claims legit?

What Is A2 Milk?

A2, like A1, refers to a variant of the predominant protein in milk – beta casein. These variants differ depending on the genetic profile of the cow producing the milk. Here in the U.S., most dairy cows happen to make milk that contains about equal amounts of A1 and A2. In other parts of the world – including Asia and Africa – the local cow stock is more likely to produce milk that has only the A2 form of beta casein. Whether a cow produces A1 or A2 (or some combination of both) is related to a spontaneous genetic mutation believed to have occurred thousands of years ago; it is not related to modern genetic engineering according to reports published in

In biochemical terms, the difference between A1 and A2 beta casein is minuscule; it boils down to a difference in the location of one single link in a protein chain containing over 200 links. But in practical digestive terms, this teensy difference could theoretically have important implications.

What Does the Research on A2 Milk Say?

When A1 (but not A2) beta casein is broken down, a shorter protein chain (peptide) called beta-casomorphin (BCM-7) is created. It is this BCM-7 protein – and the question of whether it has bioactive effects in the body – that’s at the heart of the story of A2 milk. Proponents point to research suggesting that BCM-7 may have a mild opioid-like effect in rodents’ guts, slowing down intestinal transit time. If this effect was to hold for at least certain people as well, the theory goes, it could account for a constipating effect of dairy. However, quality research data on the effects of BCM-7 in the human gut is extremely limited, and almost all studies on the topic are conducted in rodents.

Another theory in support of A2 milk is based upon other studies that have suggested that A1, but not A2, may be inflammatory in a variety of ways both within and outside the gut. If an inflammatory effect of A1 were to be more firmly established, it could help explain the reported phenomenon of post-dairy consumption stomach pain in susceptible people. However, the current data relies heavily on correlations that have not been well-controlled.

Based on what I’ve seen in my practice, the premise of this research resonates to some degree. For years, I’ve encountered patients who describe a fraught – but inexplicable – relationship with dairy. Some talk about terrible stomachaches that come on minutes after eating a dairy food, which is far too quickly to be attributable to lactose intolerance. Other patients swear they can tolerate dairy foods perfectly well when traveling abroad to Europe or Asia, but in the U.S., dairy bothers their stomachs. (They typically attribute it to foods elsewhere in the world being less “processed” than our food here in the U.S.) Many others find dairy to be very constipating, which is the opposite of what I’d expect to see in a case of lactose intolerance. While I believe my patients’ reports, I’ve always struggled to explain the reason for their experiences.

But while the theory that there’s a meaningful digestive difference between A1 and A2 milk in living, breathing human beings is promising, actual evidence to support it is still very preliminary and limited. The entire body of research in humans only consists of a handful of studies that involve a few dozen participants who already have self-identified trouble digesting milk. Some tiny studies have been too poorly designed to draw any reasonable conclusions from. But among the better-designed, blinded and controlled research studies is a small pilot study including 40 Australian women who tended to experience firmer stools and a higher likelihood of abdominal pain when they consumed A1 milk than when they drank A2 milk. There was another studyinvolving 45 Chinese adults with a history of “milk intolerance” that similarly found A2 milk to provoke less severe symptoms of abdominal pain, bloating and other unpleasant digestive symptoms than A1 milk. Both studies were associated with the A2 Milk Company, the leading player in the A2 milk industry.

Even if additional, larger, well-designed research studies bear out the finding that A1 milk can have a more constipating or abdominal pain-provoking effect compared to A2 milk, we still wouldn’t know how many people are affected. Are we talking 1 percent of the population? Five percent? Twenty percent? More? Right now, it’s anyone’s guess.

Is A2 Milk Healthy?

Nutritionally, A2 milk is identical to conventional milk in terms of calories, fat, total protein content and lactose (milk sugar), so there would be no obvious advantage to switching over for people who enjoy and tolerate the dairy foods they’re currently consuming – particularly given the price premium at which A2 milk is marketed. It tastes the same, too. To my knowledge, there’s no A2 yogurt or cheese currently marketed in the U.S. However, if you’ve got an Instant Pot or other electric pressure cooker, slow cooker or yogurt maker, you can make your own homemade A2 yogurt with one of many recipes available online.

With all of these caveats aside, if you love dairy – but even lactose-free dairy doesn’t seem to love you back – I see no reason not to try testing the A2 milk waters. It is more nutrient dense and less processed than most plant-based milk alternatives, so if you tolerate it comfortably, it could be a beneficial addition to your diet. Until researchers can offer more concrete answers as to who may benefit most from A2 milk, however, you’ll just have to be your own science experiment.


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