Oh dear another one. "Whether we can digest meat or not has no relevance to whether we *should* kill animals to do it -- that is an ethical question. And since meat is not necessary at all, the answer to that question is obviously "no"" You are wrong we are designed to eat both, therefore we should. It's not unethical to kill animals as they are a food source. With your logic it's unethical for Lions to kill and eat antelopes etc. We are after all animals. "Your argument that vitamins aren't natural is also flawed. Just because something isn't natural, doesn't mean it isn't [i] beneficial[/i] -- if you were consistent with your logic, you would be against all forms of modern medicine. Would you turn down vaccines, antibiotics and life saving treatments because they aren't "natural"? I hope not." I never said vitamins are unnatural, to supplement something that is a natural food source with vitamins is unnatural. That has noting to do with medicine. "We don't know whether lentils can suffer, but we have no good reason to believe they can. They have no brains for consciousness and no nervous systems to feel pain. Animals, on the other hand, clearly have both these things. It is the obvious rational decision to eat a plant instead of an animal." You assume to much, it's proven that plants do have a nervous system and a brain of sorts otherwise they couldn't survive. Just because we cannot translate how plants communicate, i.e how they speak, this doesn't mean they cannot feel pain just because they cannot tell us.