For any animal on this planet, you should feed them what they are designed to eat. For humans that is meat and that is because:
1. Carbon nitrogen isotope analysis in bone collagen prove we ate a diet of 80%+ meat between 20000 yrs ago to 2 million years ago.
2. Our stomach acidity is the same as meat scavengers and higher than purely carnivorous animals
3. We have a large small intestine compared to other primates (meat is digested in there)
4. Our cecum is a vestigial organ for fermenting fibre. (vestigial = we dont use it no more)
5. All humans crave meat instinctually. Children hate vegetables, cavemen painted animals on walls (not fruit or veg)
Video - plants are trying to kill you