Cow’s milk has had a tough couple of decades. And I’m not just talking about oat and almond milk stealing dairy’s thunder. Depending on which studies and articles you read, milk is either good for you or bad for you. On one hand, it’s full of protein and calcium. On the other, it’s high in saturated fat and sugar. Not to mention, it’s the alleged cause of many farts. But what if cow’s milk has just been misunderstood all these years?

Since the early 2000s, dairy companies have been peddling a type of milk known as A2. It began to gain traction after a couple of New Zealand scientists, Bob Elliott and Corran McLachlan, discovered in 1993 that the variety seemingly did not have the same health effects as regular supermarket brands—which had been linked to diabetes and a range of other digestive issues. While there’s been plenty of argument over their validity, some studies have shown that A2 milk (which lacks a specific protein that sets it apart from other milk) might be more digestible for people who experience symptoms of lactose intolerance. 

Because of its tummy-friendly reputation, A2 milk is on the rise. While the Asia Pacific region still dominates the burgeoning market, A2 milk is gaining a meaningful share of American dairy aisles: Sales are expected to grow by 18.6% between 2022 and 2027. The a2 Milk Company Limited, which launched in New Zealand over two decades ago, nearly doubled its US revenue between 2019 and 2020, despite charging a premium—and its distribution grew by almost 3,000 stores (which now include Whole Foods, Kroger, and Target).

There’s no doubt A2 milk is making a splash, but is it really better than the regular stuff? Here’s everything you need to know before your next grocery run. 

A2 describes a variety of milk which is free of A1. Surprisingly, neither are Star Wars characters: Both A2 and A1 are types of beta-casein, a protein that’s found in all mammalian milk, says Keith Woodford, an honorary professor of farm management and agribusiness at New Zealand’s Lincoln University. Originally, all milk contained only A2. But a chance genetic mutation, which likely happened thousands of years ago, has resulted in many cattle now producing mostly A1. “It’s a remarkable anomaly,” says Woodford. 

These days, cows of all breeds produce either A1, A2, or a mix of both proteins. “However, the natural level of A2 is highest in Jersey and Guernsey cattle, whereas it is much lower in Holstein-Friesian cattle,” says Woodford. 

Though A2 milk is growing in popularity globally, it’s still just a drop in the US market: Most commercially available dairy products still contain a mixture of both A1 and A2 proteins, says Alec Jaffe, the founder, CEO, and product developer at Alec’s Ice Cream, which makes all of its flavors using A2 milk. That’s because most of our milk comes from Holstein-Fresians, which produce the highest levels of A1 beta-casein, says Woodford. Any A2 milk on the market comes from “cows that have been selectively bred” to only produce that type of beta-casein, says Dennis Savaiano, PhD, a nutrition professor at Purdue University in Indiana.