Not only is an animal-based diet destructive to the body from a nutritional standpoint (and thus has consequences on the mind and soul) but it seems to me that (at least I believe so) contributing to the creation of such a tremendous amount of suffering must also have a karmic repercussion on the person who engages in it... Even from a purely metaphysical standpoint, I don't believe that ingesting and putting in your body the flesh or secretions of an animal who has spent her entire life in fear and agony can produce any favorable effect on someone.