I'd say meat. It can be quite appetizing, but it's far from healthy. Recent evidence shows that meat consumption has been linked to heart disease, cancer, diabetes, osteoporosis, and many other degenerative diseases. Aside from the well-known, it's practically common sense that meat was never intended to be consumed by human beings. Just take a look at the structure of our teeth and you'll see what I mean. Human teeth are rounded, and/or quadratically shaped. Almost every creature in nature who has rounded teeth consume vegetation and have a non-flesh appetite. This is nature's indication that we (humans) are natural plant eaters. Only creatures with sharp, pointy, blaze-like teeth consume animal flesh; e.g. lions, hyenas, bears, wolves and other wild beasts. Horses, Elephants, deers and many herbivores have teeth similar to ours, and their lifespan is relatively long.