from:
diabetesqld.org.au/media-ce...
A1 beta-casein, on digestion, releases a peptide (protein fragment) which has opioid and inflammatory characteristics. The protein fragment is called beta-casomorphin-7 ("caso" from casein, "morphin" from morphine-like, and 7 to indicate the fragment contains seven amino acids).
The release of this protein fragment is accepted science; it is the implications that have been controversial. There is scientific literature that links A1 beta-casein to multiple health conditions....
I was somewhat confused by Laurie Mischley's diet study which found that supplementation with calcium had a mildly beneficial effect on Parkinsons. If that is the case then maybe it is the inflammatory effect of the A1 that is bad for leaky gut (and Parkinson's sufferers). You can get A2 milk (and goats produce is A2 anyway).