You may be right, but we cannot subject human beings to the type of research that would prove plant-based diets are superior or equal to meat-based. I'm not a food scientist, but I'm assuming that you have more than a passing interest in this. Then you also know that we cannot duplicate anything like the research done by Dr. Keyes with the starvation experiments. Yes, we are left with a lot of observational data and we must use that to make intelligent decisions about our health.