"Recently, a relationship between disease risk and consumption of a specific bovine β-casein fraction with either A1 or A2 genetic variants has been identified. BCM7 is suggested to be associated as a risk factor for human health hazards as it can potentially affect numerous opioid receptors in the nervous, endocrine and immune system.
It is also known to be an oxidant of low dietary lipoproteins (LDL) and oxidation of LDL is believed to be important in formation of arterial plaque. Epidemiological evidences claim that consumption of beta-casein A1 milk is associated as a risk factor for type-1 diabetes, coronary heart disease, arteriosclerosis, sudden infant death syndrome, autism, schizophrenia etc.[3,4]
A broad range of studies from American and European investigations has shown reduction in autistic and schizophrenic symptoms with decrease in A1 milk intake. Further, animal trials have also supported the linking of type-1 diabetes to milk exposure in general and A1 beta-casein in particular.
"Populations, which consume milk containing high levels of β-casein A2 variant, have a lower incidence of cardiovascular disease and type-1 diabetes. The A1/A2 hypothesis is both intriguing and potentially very important for public health if it is proved correct. "
Read more: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3475924/
What can you do? A2 milk is found from heritage breed cows like Guernseys, Jerseys, and goat. Local raw milk seems to be of the heritage breed type and most likely the A2. Each herd can be different, so you may want to ask your dairy producer if they have tested their herd for their variant.
Following Weston A. Price