I was talking with my neighbor this weekend and he was saying that he had been a vegetarian for nearly ten years but began eating chicken again around a year ago. I asked him why and he said that he was running marathons at the time and couldn't keep enough weight on. He said that humans are able to absorb only 40-70% of plant protein but 90% of animal protein. Is this right? Couldn't a person just eat more plant protein instead of eating meat? I've never heard of anyone getting too little protein but a co-worker told me the same thing a few months ago; she was a veg for about 8 months and then began eating meat again when she started running. I'm just curious because my neighbor seems very informed and yet I couldn't imagine eating chicken after several years of not eating it.