A1 vs A2: Does Casein Type Matter in Cow’s Milk?

A1 vs A2: Does Casein Type Matter in Cow’s Milk?

In This Article

Protein in Milk

Milk might do a body good, but a new trend in milk production may have us thinking twice! The issue is around the type of casein protein that is found in milk from different breeds of cows. Some breeds might be better than others. Casein makes up about 80 percent of the protein in milk, and there are numerous varieties of it.

Most milk comes from cows that have both A1 beta-casein and A2 beta-casein, but some breeds of cows provide only the A2 variety. Guernsey, Jersey, Charolais and Limousin cow breeds have milk that is more predominantly or exclusively A2 beta-casein. (10) Some studies suggest that the A1 beta-casein is much harder to digest, and could be the cause of many cases of dairy intolerance. (8)

In Europe and in parts of the US you can find A2 milk products and, while many swear it is easier to digest, the science is inconclusive. The question: Is this a fad or a fact? To investigate this, the European Food and Safety Authority (EFSA) did a thorough evaluation of the A1 and A2 dairy products and found that there was no conclusive evidence that the A2 casein product was easier to digest or superior in any way to the A1 casein. (1)

What Makes A1 Milk Different Than A2 Milk?

The culprit that suggests that A1 beta-casein milk is less healthy than A2 beta-casein milk is an opioid called BCM-7. Contrary to what the EFSA found, there are a handful of observational studies that suggest the A1 beta-casein may be less healthy. One study linked a lower consumption of A1 milk to a lower incidence of diabetes. (2)

There are also studies that suggest that both the A1 and A2 beta-caseins in dairy are actually protective against diabetes – suggesting that any conclusion at this time may be premature. (3)

One study suggested that the A1 beta-casein may increase the risk for heart and arterial health concerns, but this study was done with rabbits who are vegetarians and typically do not consume milk. (6) In one of the only human studies, there was no difference between the A1 and A2 beta-caseins on blood vessel function, blood pressure, blood fats and inflammatory markers. (4)

The New Zealand and Australian Food Safety Authorities also did a review of the science and stated that there is no difference between the A1 and A2 beta-caseins with regard to heart disease and diabetes risk. (5)

Infants May Be More at Risk

Many of the studies suggesting that A1 milk produced an increased risk for heart, blood sugar and cognitive concerns were done with infants, who are more susceptible to the BCM-7 opioid peptide in A1 milk. (7) Studies have shown this opioid is not absorbed into the bloodstream of adults, who are therefore not at risk. (9) This may suggest that cow’s milk is not an ideal substitute for infants, and mothers in need of supplemental milk might consider goat’s milk or A2 dairy.


At this time, it seems premature to suggest that the A2 milk is a better choice for adults. I would first suggest you try non-homogenized and vat-pasteurized milk, as I have suggested in my previous articles. If that does not work and dairy is still provoking digestive trouble, consider the A2 dairy products. That said, the sensitivity of this opioid is typically problematic when it passes through a broken down intestinal wall. Once again, we find that our food sensitivities more often have more to do with our digestive strength, rather than the food we choose. All this said, we should always be choosing the purest unprocessed and whole organic foods whenever possible.


  1. http://www.efsa.europa.eu/en/efsajournal/pub/231r
  2. http://www.ncbi.nlm.nih.gov/pubmed/16407643
  3. http://www.ncbi.nlm.nih.gov/pubmed/12242456
  4. http://www.ncbi.nlm.nih.gov/pubmed/16441926
  5. http://www.ncbi.nlm.nih.gov/pubmed/15867940
  6. http://www.ncbi.nlm.nih.gov/pubmed/12957678
  7. http://www.ncbi.nlm.nih.gov/pubmed/19576256
  8. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4818854
  9. http://www.ncbi.nlm.nih.gov/pubmed/3958290
  10. http://www.ncbi.nlm.nih.gov/pubmed/17666771

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