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Milk consumption has plummeted over the past couple of decades as consumers have increasingly turned to plant-based, dairy-free alternatives made from almonds, coconuts, oats, soybeans, and flaxseeds. According to market-research company Mintel, sales of nondairy milk increased 61 percent in the United States from 2012 to 2017, while sales of dairy milk fell 15 percent during that same period.

One bright spot, however, is A2 milk, a type of cow’s milk with only A2 beta-casein proteins that is being marketed as “easier on digestion” than the milk commonly sold in the United States, which is a mixture of A1 and A2 proteins. Although research is in its early phase and the National Milk Producers Federation has challenged claims that A2 milk is easier on the gut, companies — and consumers — are climbing on the A2 bandwagon. The New Zealand–based a2 Milk Co., which sells its a2 Milk in New Zealand, Australia, the United Kingdom, and China, launched its products in the United States in 2015. As of January 2018, the company had distribution in about 6,000 stores across the country, and its revenue grew about 70 percent last year.

Supporters of A2 milk contend that millions of Americans who experience digestive issues when they drink milk — think bloating, flatulence, and diarrhea — might actually be unable to digest A1, a protein commonly found in milk from Holstein cows which are, by far, the most common dairy breed in the United States. “The A1 protein is much less prevalent in milk from Jersey, Guernsey, and most Asian and African cow breeds, where, instead, the A2 protein predominates,” reports Mother Jones.

A1 milk makes up almost 100 percent of the milk sold in the United States — in short, if you have milk in your fridge right now and you didn’t specifically seek out the A2 variety, it probably contains A1 proteins.

What is A2 Milk?

So, what exactly is A2 milk — and is it a healthier choice, even for those who have problems digesting milk? A2 milk is not a new nondairy milk alternative, like soy, oat, or almond milk, or a Frankenstein milk-hybrid whipped up in a lab. It is natural cow’s milk. In fact, before cows were domesticated, they produced only A2 milk. What makes A2 milk different from the A1 milk that dominates most U.S. dairy cases is that it has a slightly different protein profile.

The primary protein in all cow’s milk is casein, and it is found in cow’s milk in several different forms. The three major forms are alpha casein, beta casein, and kappa casein.

The U.S. commercial dairy industry gets milk primarily from Holstein cows — and Holstein cows primarily produce A1 milk. For many years, that was that. No one thought about the protein profile of cow’s milk one way or the other.

About 60 years ago, scientists discovered genetic differences within each of the three casein protein groups. They showed that each group — alpha, beta, and kappa — has its own subgroups that are distinguished by slight genetic variations. A1 and A2 refer to two of at least 13 subgroups of beta casein.

Typical U.S. milk has a mix of A1 and A2 beta casein. A2 milk has only A2 beta casein. (Interestingly, human breast milk also contains only the A2 protein.) Everything else about A1 and A2 milks is the same: They both contain alpha and kappa proteins (and their subgroups), other beta casein subgroups, and lactose. Different cows naturally produce one or the other of the milks; nothing has been genetically engineered. Taste- and appearance-wise, the two milks are identical.

Anecdotes about A2’s easy digestibility abound. Some people who experience digestive distress when drinking traditional A1 milk have reported an easier time digesting A2 milk. National and regional media outlets in the United States have started reporting on the phenomenon. U.S. dairy farmers are hoping to capitalize on A2’s purported benefits, and gourmands are starting to show interest.

“I’ve seen some people tolerate milk from A2 cows more easily,” says Liz Lipski, PhD, director of nutrition and integrative health at Maryland University.

A wealth of objective scientific data, however, lags behind. Most of the existing research has been conducted or funded by the producers of A2 milk. “Almost all the work going on here is funded by the A2 milk company,” says John Lucey, PhD, professor of food science at the University of Wisconsin–Madison. This doesn’t mean the research is biased, nor does it negate the anecdotal evidence that A2 milk may be easier on the GI tract, but so far we are lacking robust studies that could support definitive health claims.

“It’s possible that the peptide differences in A2 milk may make it easier for humans to digest,” says Don Otter, PhD, senior outreach specialist at the Center for Dairy Research at the University of Wisconsin–Madison, but “there’s no robust scientific proof yet. Right now, it all comes down to the individual consumer experience. Do they feel A2 milk is easier to digest?”

Adds Lipski: “Anecdotal evidence isn’t bad. It’s where all science begins. But no one has done research yet. Overall, this debate needs further investigation.”

Is A2 Milk Easier to Digest?

As researchers dig into the differences between A1 and A2, the best thing for interested consumers to do is to test the A2 waters. “We don’t have the research to back it up; that’s the bottom line,” says Lipski. “But it’s an interesting hypothesis, so try it. See if it works for you.”

For a true test of your potential reactivity to A2, go off all dairy for a month to clear the casein from your system. Then try A2 and pay attention to any symptoms — or lack thereof. (Also, remember that milk from goats, sheep, and water buffalo contains only A2 proteins, so if you can more easily digest A2 cow’s milk, you might want to try dairy products, including cheese, made from the milk of these animals. Some producers are starting to make cheese from A2 cow’s milk as well.)

Keep in mind, though, says Lipski, that A2 milk contains lactose, just like A1, so you will still notice side effects if you are lactose intolerant. “Lactose is lactose is lactose,” she says, adding that “some people don’t tolerate any dairy no matter what.”

You’ll also face the more general problems that accompany most dairy products. For example, any dairy product that’s been pasteurized, whether it’s A1 or A2, is heat-treated in a way that denatures the milk’s proteins and makes them more allergenic for some people, notes Lipski. Also, nonorganic dairy can be high in antibiotics and environmental toxins, and what cows are fed can change the nutritional profile of the milk they produce, sometimes in ways that are less healthy for human milk drinkers.

So choose your dairy wisely — whether it is A1 or A2 — and if dairy gives you trouble, or if you’re concerned about the other potential health concerns linked to dairy, limit or eliminate it from your diet.

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