The difference between regular and A2 milk is variation in one of the major milk proteins: ß-casein. The two main versions of ß-casein are A1 and A2, giving the A2 milk its name. ß-casein consists of 209 amino acids and the A1 and A2 varieties differ by just one amino acid. Most milk contains both A1 and A2 varieties. The A1/A2 ratio depends on the cow breed. A2 milk is claimed to be free of A1. Hettinga evaluates the supposed health benefits of A2 milk: chronic disease, cow milk allergy and intestinal discomfort.
Chronic disease and BCM-7
EFSA concluded in 2009 that the ratio A1/A2 in milk is not plausibly related to chronic diseases. Earlier, in the 1990’s and early 2000’s, a breakdown product of ß-casein ‘BMC-7’ was linked to chronic disease. Originally, this was based on epidemiological studies, but on further investigations, these studies turned out to be unreliable. In animal studies, BCM-7 was directly injected in the blood stream of animals which resulted in negative health effects. However, these negative effects were never found in studies where humans consumed the casein. Probably, BCM-7 is broken down in our intestinal tract and does not enter the blood stream.
Cow milk allergy
A lot of farms selling A2 milk directly to consumers claim that A2 milk helps against cow milk allergy. Hettinga though, does not expect anyone with this allergy to benefit from consuming A2 milk, because hardly any person with cow’s milk allergy is allergic to ß-casein alone. Also, only one amino acid has been changed. Moreover, Hettinga has never seen evidence for a benefit of A2 milk in double blind provocations, which are the most suitable studies to prove an allergy. Studies based on self-diagnosis did report benefits, but these are known to be very unreliable in studying food allergy.
Intestinal discomfort
Recently, a new hypothesis has popped up: the ß-casein A1 variant may be related to intestinal discomfort. This “illness” is difficult to categorise and very popular for products that can’t make strong claims. Intestinal discomfort may originate from lactose intolerance, which is the sugar that is present in milk. All milk, though, contains lactose and therefore this discomfort is independent of A1/A2.
There are also people with undiagnosed weak symptoms. Among these people gluten-free products are also popular. A small-scale study on 45 Chinese people showed a small decrease in intestinal discomfort after consuming A2 milk for 2 weeks. However, many small-scale nutrition studies, which have low number of participants and/or short intervention, are not very reliable. Also, the results are likely to be different for Europeans who suffer less from lactose intolerance. According to Hettinga, “we have to wait for stronger proof before we can make conclusions about the effect of A2 on intestinal discomfort.”
Primeval cow
In the Netherlands, the A2 milk is marketed as coming from primeval cows. Also in other countries, marketing emphasises that A2 is the original ß-casein, and A1 is the version that comes in our current milk due to breeding. A1 can be found in many cow breeds, not only modern breeds. Moreover, the regular milk from the Dutch high productive Holstein cows even contains twice as much A2 than A1.
About the author
Kasper Hettinga is specialised in milk protein biochemistry. At the moment, he for example looks into the effect of heating on milk proteins, and the differences between milk from cows with horns and without horns. Use the get in section below if you like to get in touch with him.
Reference
This article was adapted from Kasper’s blog ‘Is A2 milk going to make us healthy?’ posted on 13th October 2016 on ‘Dairy Science & Technology Blog’.
