"In people who have been long-term vegetarians, studies have found that they actually lose the ability to digest meat". Is this true, at a biological level? (As opposed to any possible psychological effect.)
(Yes, the link is from the SciFi SE, but I'm sure there are plenty of vegetarian sites that would make the exact same claim.) I actually came to skeptics expecting to find a counter-response already, that I could link in to the SciFi post - I can't believe someone hasn't already asked this. :)
Another claim: Why do long-term vegetarians find it difficult to digest meat? - by Dr. Mehmet Oz, who is Professor of Surgery at Columbia University.