Cow’s milk gets a bad rap. Over the past few decades, it’s been maligned for everything from fat and sugar levels to synthetic-hormone and antibiotic content. It has faced fierce competition from alternatives like almond milk and soy milk. But what if the most dangerous thing in a glass of milk all this time has been something much more elemental?

This was the question puzzling the New Zealand scientists Bob Elliott and Corran McLachlan in 1993, when their studies of Type 1 diabetes and heart disease pointed to milk as an unlikely culprit—specifically, a variety of milk known to scientists as A1, the ubiquitous variety stocked in most of the world’s grocery stores. A1, the research suggested, produces inflammatory compounds in the human digestive system that can cause mild symptoms like stomach pain, or much worse.

The research also showed, however, that a second type of milk—a variation known as A2—did not have these effects. McLachlan posited that A2 could be better for overall health, and maybe even digestible by those who consider themselves lactose intolerant.

In 2000, McLachlan teamed up with the billionaire farmer and entrepreneur Howard Paterson to found the A2 Milk Company, or A2MC, with the goal of breeding more A2-producing cows and putting A2 milk in Australia and New Zealand’s retail markets. Their efforts came under almost immediate scrutiny. Aussie milk drinkers were alarmed by the implication that they’d been drinking a harmful product, and the region’s commercial milk producers feared a revolution against their livelihood. Moreover, most of the studies that found health benefits from drinking A2 milk were commissioned by A2MC itself.

To skeptics, the public-health campaign looked like a money grab.

Seventeen years later, this war of competing interests has only intensified. As biased polemics continue to muddy the waters of the research surrounding the discovery, A2MC has managed to secure some 12 percent of the Australian dairy market. They have entered markets in China and western Europe, and predict a full U.S. rollout by 2018.

While American commodity farmers have been every bit as territorial as their Australian counterparts, some small farms have begun converting their herds over the past few years, sliding A2 genetics into their portfolio of value-adding concepts like grass-fed and local. At a time when American grocery stores stock far more varieties of plant-based or otherwise specialty milk than they do commercial cow’s milk, these small-scale farmers have a built-in receptive audience.

Now, A2 milk stands poised to take these niche markets by storm—but first American consumers will have to be convinced that it’s actually good for them.

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The split between A1 and A2 milk was discovered about 25 years ago in milk’s most abundant protein, beta-casein. The variation occurs in the protein’s chain of 209 amino acids: A1 has the amino acid histidine at position 67 in the chain, while A2 has proline there instead.

Despite its name, A2 is actually the original variety. Historians believe that the A1 mutation originated in Europe somewhere around 8,000 years ago, but why it occurred is open to speculation. Some believe that farmers began breeding for higher output at this time, and favored the A1-dominant breeds like Holsteins known for producing more milk. Others speculate that the mutation was caused by forces more cosmetic than substantive; Holsteins are the classic black-and-white cows that dot pastures throughout the western world.

“It could have been something as simple as the first cow to have a black-and-white color by chance also carried the A1 version of the gene, and farmers then said, “we like the look of these,” said Keith Woodford, an honorary professor of farm management and agribusiness at New Zealand’s Lincoln University. A2-dominant breeds wound up in Asian and African countries, possibly because they were less in-demand and relegated to cultures that consumed less milk.

McLachlan and Elliot’s big discovery back in 1993 was that A1 produces an opioid called beta-casomorphin, or BCM-7, when it hits the small intestine. A2MC’s studies have gone on to claim that BCM-7 causes inflammation that leads to myriad health issues, ranging from eczema and indigestion to diabetes, schizophrenia, and autism.

In 2007, Woodford published a book about the dangers of A1, Devil in the Milk: Illness, Health and the Politics of A1 and A2 Milk, which boosted A2 milk sales and prompted the New Zealand Food Safety Authority and European Food Safety Authority to propose rigorous analysis of A2MC’s health claims. The EFSA’s report, issued in 2009, rejected most of the evidence. It found that in “most if not all” animal studies prior to its publication,  scientists had injected BCM-7 directly into their animal test subjects, rather than administering it orally, which in the EFSA’s view rendered the results irrelevant to human consumption. The review also chastised McLachlan and Elliott for being too quick to link the prevalence of chronic disease in a country to the abundance of A1 cows in that country, when disease could also be explained by factors environmental, political, or cultural. In other words, correlation does not equal causation.

More studies followed, but most could be traced back to less-than-impartial funding. A biochemist at the University of Sydney wrote an oft-quoted critical review of the A2 milk hypothesis, but later admitted to being a consultant for one of New Zealand’s largest dairy corporations, Fonterra. A 2014 study conducted in the European Journal of Clinical Nutrition found that human subjects on an A2-only regimen reported less abdominal pain, but it was sponsored by A2MC. Even Woodford was a former consultant and shareholder in A2MC (though he sold his shares in 2007 to demonstrate his independence).

Luckily for McLachlan’s company, some impartial studies have returned positive verdicts for A2. In 2013, the National Dairy Research Institute in India published a peer-reviewed study, finding that mice fed A1 beta-casein produced far more inflammatory compounds linked to heart disease, eczema, and asthma than the mice fed A2 beta-casein.

(Courtesy of A2MC)

A2MC has opted to focus on the digestive advantage of their product in their current marketing, for the most part steering clear of incendiary claims about more serious health conditions. Their efforts remain robust, and they project a positive outlook that belies the difficulty they’ve had gaining worldwide trust; they even put a positive spin on the EFSA’s critical report on their website, highlighting the report’s agreement that A1 and A2 are, in fact, digested differently. A2MC’s milk can now be found in five countries and nearly every grocery chain in Australia. They have 20 farms producing milk for them in the U.K. and four in the U.S., where they’ve partnered with Sprouts, Whole Foods, Kroger, and Albertson’s stores. Their primary focus in the U.S. is California, which Blake Waltrip, the U.S. CEO of A2MC, calls a “ripe market for dairy disruption.”

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American dairy lobbies remain skeptical, though. Both the Dairy Farmers of America and the National Milk Producers Federation are aware of the trend—and dismissive of it. “If interest continues to grow, we will explore opportunities for A2 milk with our dairy farmer owners and customers,” says David Darr, the General Manager of Farm Services at DFA. Chris Galen, the Senior VP at NMPF, showed marked concern about the lack of substantive evidence in favor of the theories.

Since A2 milk hit shelves in California in 2015, worries within the American dairy industry have mirrored those of commodity farmers Down Under, where A2 has already outstripped organic milk sales. Mainstream American dairies have expressed concern about how the introduction of these products will affect their existing product sales. “Shifting to A2 creates big problems for how to sell the ‘normal milk’ during the transition,” Woodford, the Lincoln University professor, said.

But this internecine strife between lobbyists, scientists, and large-scale dairy operations has left a window for artisan farmers, who are used to brokering the varied specialty interests of their customers. For their crowd, Big Dairy opposing a product is almost reason enough to look into it.

“Neither position seems to have the support of mainstream science, and yet producers like us can be compelled to change the way we do things simply because of our customer’s preferences,” said Andy Hatch, the head cheese maker at award-winning Upland’s Cheese Company in Wisconsin. “I once heard an organic farmer say that he’d milk his cows in a pink tutu if his customers paid him more for it.”

That rationale has inspired many forays into the new frontier of A2 cow-breeding, while other American farmers are putting sincere stock in the product’s health claims. Warren Taylor, an American A2 farmer and owner of Snowville Creamery in Ohio, sees some of his customers’ reports of improved digestive comfort as all the proof he needs of A2’s benefits.

Whatever their reason for making the switch, these small dairy farms have to overcome one significant hurdle. Back in 2000, A2MC patented a simple DNA hair test to determine if a cow will produce A1 or A2 milk, and in 2003 bought a patent owned by Elliott that tested liquid milk for presence of A1 beta-casein. These tests remain the most reliable method for farmers to be sure of the kind of milk they’re producing, but A2MC currently administers them only to U.S. farms with which they have specific partnerships.

For independent farms looking for the tests, A2MC recommends the University of California, Davis, where several A2 genotyping models are in development. These tests have their limitations, though: The cost ranges from $25 to $75 per animal, and the research team has grappled with some accuracy issues and legal kinks. At Snowville Creamery, Taylor has begun working with Ohio University to develop a less expensive polymerase chain reaction gel test, but in the meantime, he offers to pay for his farmers to test their herds.

In Massachusetts, Topher Sabot, a co-owner of Cricket Creek Farm, is keeping a close eye on the trend and would consider breeding with A2 bulls—but this willingness does not equate to a trust in A2MC. “Personally, the A2 Milk Company seems to be based primarily on marketing and playing to people’s fears,” he said. “Their milk appears to be a highly processed product that is not consistent with the local and fresh-food movement that I have experienced in the U.S.”

For now, this mixed attitude toward A2 genetics prevails in the U.S. A2MC could be on its way to changing the world, or cresting toward a quiet end. With the company shooting for a full presence in the U.S. market by next year, consumers have reason to hope that more research will be conducted before the onus is on them to make the call.