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A2 Milk: Healthy or Hype?

Submitted by Sarah Lange

Edited by Marcia Bristow MS RDN CSSD CD

If you take a trip to your local grocery store, you will likely find A2 milk in the dairy coolers. A half-gallon of A2 milk is 85% more expensive than the conventional milk on the neighboring shelf, so what is all the hype and is it worth the price? There are many different nutrition crazes and fads circulating on the internet, in magazines, and on social media, and A2 milk is just one of the latest trends to hit the market. A2 milk is milk that contains a specific type of protein and is supposedly easier to digest. Who would have guessed that the genetic makeup of the cows your milk comes from would be one of the newest crazes?

Casein, the largest group of proteins in milk, accounts for about 80% of the total protein content. While there are several types of casein found in milk, beta casein is one of the most common forms. Beta-casein exists mainly in the A1 and A2 forms.1 Regular cow milk, that you would find in any grocery store, contains a mixture of both A1 and A2 beta-casein. The ratio of Al to A2 depends on the type of cow the milk comes from, but it is generally about 50/50.1

Before cows were domesticated, they only produced A2 beta-casein protein. At some point after they were domesticated, a natural mutation occurred of a single gene in Holstein cows, resulting in the production of A1 beta-casein.1 While milk from some types of cows, such as Jersey cows, still contains mostly A2 beta-casein, milk from Holsteins contains mostly A1. The most common dairy cow breed in Australia, Northern Europe, and the United States is the Holstein, meaning most milk on grocery stores shelves contains A1 beta-casein.1

Since A1 and A2 proteins are built slightly differently, it is thought that they differ in digestibility. Given the structure of the A2 protein, it may be easier to digest. Scientists believe that the structure of the A2 protein is easier for everyone to digest, but may be especially beneficial for those who are lactose intolerant.2 One of the byproducts of A1 protein, beta-casomorphin (BCM-7), is believed to cause inflammation, which could be a main contributor to gastrointestinal problems.1 While scientists agree on the structural differences between A1 and A2 proteins and that the structure of the A2 protein makes it easier to digest, the research is just beginning on the impact of these variations on the human body and, thus far, the evidence of any health benefits remains unclear.

The a2 Milk Company, and others, have capitalized on the prospects of A2 milk providing gastrointestinal relief for consumers who find regular milk difficult to digest. Many people who have difficulty digesting milk think it is because of the lactose, but it is possible that their symptoms could be from the A1 proteins.2 However, the evidence on this claim is sparse. The a2 Milk Company funded a study in China in which 600 adults who reported lactose intolerance were randomly assigned to drink either regular milk or A2 milk. Participants drinking the A2 milk reported less severe bloating, gas, and abdominal pain, but only slightly less than the participants drinking the A1 milk.2

The bottom line is that the science either isn’t there yet to support the health benefit claims of A2 milk or the benefits simply do not exist. Until more research is conducted, and not funded by A2 milk companies, it is probably not worth doling out the extra cash for A2 milk.


  1. Truswell AS. The A2 milk case: a critical review. Eur JClin Nutr. 2005;59(5):623-631. doi:1038/sj.ejcn.1602104
  2. He M, Sun J, Jiang ZQ, Yang YX. Effects of cow’s milk beta-casein variants on symptoms of milk intolerance in Chinese adults: a multicentre, randomised controlled study. Nutr J. 2017;16(1):72. doi:1186/s12937-017-0275-0
  3. Image from: www.happymilk.in/a1-vs-a2-milk/

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