I'm not reasoning that all foods are equally beneficial and harmful, and I accept that it may very well be that a plant-based diet is superior to a meat-based diet. I reject the idea, however, that we know enough to say that this is true, and I absolutely reject the idea of significantly changing behavior based solely on epidemiological studies -- the epidemiological studies should be the starting point for much further study. To date, most large-scale controlled studies on diet have unfortunately been shelved. It should entirely be possible to separate multiple groups on multiple different diets and see what happens over a period of, say, ten years -- one diet as vegetarian, one diet as meat/fruit/nut but no grains, a fish+vegetarian diet, while holding other variables constant (such as calories). This is what we need to do to know, and this is what has consistently been proposed, but not done.