A. John Leung, MD, an allergist, gastroenterologist, and director of the Center for Food Related Diseases at Tufts Medical Center, explains, “A2 milk is almost identical to the milk you are used to seeing, with one small difference. The designation ‘A2′ refers to a particular configuration of casein protein. Until recently, most milk sold in the U.S. came from cows that naturally produce both the A1 and A2 forms of this protein. Some companies are now marketing milk from cows that naturally make only the A2 form. The A2 form differs from the A1 form by just one amino acid.”
“In their advertising, the A2 milk companies reference research suggesting that A1 proteins are linked to digestive problems, but the overall body of research is inconclusive. People who are lactose intolerant do not produce enough of the enzyme lactase to break down lactose. The intact sugar is then fermented by microbes that live in the gut, producing the uncomfortable, unpleasant symptoms.”
“People with lactose intolerance will not benefit from A2 milk. It is also not safe for infants with cow’s milk protein allergy and adults with known milk allergy. Marketers of A2 milk claim that some people will have less digestive discomfort if they switch to A2 milk. In my practice, I do not recommend A2 milk. Instead, I recommend lactose-free milk (such as Lactaid) for people who have lactose intolerance. If a trial of lactose-free milk fails to relieve symptoms, there might be a problem other than just lactose intolerance, and one should seek medical care.”