Most plants have developed some method for avoiding consumption by predators, be they insects or mammals wishing to kill and eat them. For most plants, the defense has been to develop some sort of poison, making it especially strong in or near the seed. Mostly, these poisons are effective on insects, but they are effective on us, too. For example, nicotine is an effective insecticide, and has mind altering effects on us as well. It kills insects, and it just fucks us up a little bit. Same for the caffeine that is ubiquitously used in nature to defend seeds from insects. Most notable is the coffee tree's seed.
Some plants are "creative," designing their poisons to work on some animals (the ones that can digest their seeds) and not work on other, smaller animals that cannot digest the seeds. Hot pepper plants do this with capsaicin--mammals detect the chemical and it triggers heat sensing nerves in the mouth. Birds, on the other hand, cannot detect the capsaicin and eat the peppers and their seeds happily, pooping out the seeds as they fly all over the place, with a nice dose of fertilizer mixed in. (Human digestion destroys the seeds).
But almost every plant has some kind of poison to defend itself, and almost every animal has some other method for keeping itself from becoming food--horns, fangs, armor, stealth, camouflage, or an ability to run very fast. So most animals defend without a poison in their flesh, which seems to me to indicate that if we can avoid an animal's other defense mechanisms, its body is likely to be some of the best food available to us (or at least the least psychoactive). Perhaps eating all these plant-based diets is causing us to slowly poison ourselves and die, which seems fitting if you think about the "goal" of the plants we consume--to poison their would-be murderers sufficiently to dissuade them from killing and eating the same type of plant in the future.
And both plant and animal bodies contain vital nutrients that we need in order to live--but we can live either one if we so choose. I think perhaps one of the reasons we do not do very well on a high-meat diet is that modern intake of meat is basically "processing" the animal in the same way that we process wheat to remove the husk, yielding white flour. We process the animal and consume only its muscles--only one part of the animal--and the rest of the plant, and the rest of the animal, both contain nutrients that we now seek out--like omega 3 oils, fiber (which might not be a great idea), enzymes, and so on.
Further, we know that proteins form natural antibiotics (antimicrobial peptides) during digestion. We also know that certain amino acids act as powerful antioxidants that support immune functions. For example l-arginine reverses liver damage in heavily alcoholic rats, and N-acetylcysteine (a form of l-cysteine, and amino acid produced during protein digestion), is a very strong sulfur-based antioxidant that can be used to keep an avocado green, and for general immune-system support. It is also the antidote to Tylenol poisoning, and seems to be helpful for schizophrenics and Alzheimer's patients. We also know that cysteine and alanine (another amino acid) speed ethanol metabolism and bind to the toxic byproducts of ethanol metabolism (like acetaldehyde, a primary cause of hangover symptoms) in rats.
So why is there such a large focus on plant-based antioxidants? Why are animal-based antioxidants almost completely ignored today? It seems to me that proteins, especially bioavailable proteins, should be a huge focus in a healthy diet. They are anti-inflammatory, antibiotic, and help us process poisons (like ethanol) at a faster rate.
