There are distinct differences in milk produced by different breeds of dairy cow. A2 cows are descended from ancient breeds more than 5000 years ago. A1 cows are “newer” breeds that have been around for the last 5000 years & have experienced a mutation of a particular amino acid in a protein called beta casein which has a chain of 229 amino acids. A2 cows produce this protein with a proline at position 67, whereas an A1 cow has a mutated proline amino acid which converts to a histidine. The proline has a strong bond to another small protein called BCM 7; which keeps the potentially toxic BCM 7 from being released. But the mutated protein histidine, only weakly holds onto BCM 7 – and then it’s released into the tract of animals & humans who drink it. This is a likely cause of increased phlegm production in digestive & respiratory tract, which can worsen upper respiratory problems – among other problems. The book “The Devil In The Milk: Ilness, Health & the Politics of A1 & A2 Milk” goes into much more detail.
Older breeds such as the Jersey, Guernsey, Asian and African cows are primarily A2 as are goats and sheep. Herds in much of Asia, Africa and parts of S. Europe still produce A2 milk. Black & white breeds like Holstein or Friesians are A1 cows. They’re the most popular breeds in North America, New Zealand, Australia and the rest of Europe.
Cows can be a mix of A1 & A2 – and bred to produce A2 milk. It’s easily tested. So could a farmer eventually have cows of a different breed that would produce A2 milk? They might not even have to change over their herds to do this. Might be a good business for a farmer since it’s very difficult to get raw Jersey or even rarer Guernsey milk and the demand just seems to be growing. If a person has a strong immune system, they may not be affected by the toxin but others could be having a rough time. I’m going to try it and see if I do feel better. I drink so much milk – the problem is when you do find it- it’s way more expensive than cheap milk. Hmmm anybody want to go in on a cow….?
found a great article that speaks to this subject at