In his book called Plant Paradox, Dr Gundry from the US explained like this: about 2000 years ago, a spontaneous mutation in Northern European cows caused them to make the protein casein A–1 in their milk instead of the normal casein A-2. During digestion, casein A-1 is turned into a lectinlike protein called beta-casomorphine. This protein attaches to the pancreas's insulin-producing beta cells, which prompts an immune attack on the pancreas of people who consume milk from these cows or cheeses made from it. I could not believe what I saw, so searched pub med & sure enough I found the following:
Type I (insulin-dependent) diabetes mellitus and cow milk:
casein variant consumption.
An extract from this 1999 paper says: The A1 and B variants of beta-casein have a histidine at position 67 that determines the enzymatic cleavage of the molecules yielding beta-casomorphin 7. The A2 variant does not cleave at this position due to the presence of a different amino-acid (proline). Beta-casomorphin-7 has opioid properties, and has been shown to inhibit human intestinal lymphocyte proliferation in vitro. It is possible that such an immune suppressant influences the development of gut-associated immune tolerance, or suppresses defence mechanisms towards enteroviruses, both of which have been implicated in the aetiology of Type I diabetes. Other immunosuppressive effects which might contribute to diabetes include activation of endogenous retroviruses associated with the disease. Click the link below to see full abstract on medline:
Another paper included even IHD. Holy shit! Look below:
Ischaemic heart disease, Type 1 diabetes, and cow milk A1 beta-casein.
According to New Zealand research conducted by CN McLachlan, the regular intake of common milk containing A1 beta-casein inspires the development of coronary heart disease. Click the link below for full abstract:
Luckily this is still controversial. That said, Dr Gundry's case reports showed that in susceptible persons, different breeds provoke different responses.
The following is a website providing information about A1 & A2 difference: