In my opinion, it's another theory that may or may not be disproven someday. I think it's originator has already come out with new modifications in a second edition book. I read someone else's post here not too long ago about how the Blood Type Diet wouldn't be necessary if we all had healthy guts. I say listen to your body. I'm a type A and I KNOW a purely vegetarian diet isn't right for me. I need a modest amount of animal protein to feel well. Legumes don't agree with me at all, and forget about soy. So far apple cider vinegar seems great for my digestion.