An experiment I tried was going A1 casein-free for a year or so. The first couple of times I tried re-adding A1-containing Greek yogurt I felt ill, but other things happening at the time could have caused that, so no really conclusive result. I've returned to a diet high in A1 casein dairy and seem fine so either I'm not sensitive to it or else the stuff is sneakily doing something I haven't discovered yet. Nearly all my current dairy is fermented stuff (Greek yogurt and home-grown kefir). I wonder if that has any effect? Not presently much into any cheese.