Moreover, all of the higher functioning animals are either omnivores or carnivores – which makes a bit of sense since it presumably takes more cunning to stalk prey than to run. An interesting corollary to this is that our brains need fats to function well, and there is strong evidence that low fat diets contribute to Alzheimers and other brain disorders. Animals are, of course, not the only source of fats, but they contain a higher concentration of fat than virtually all vegetable foods.
While researching and writing my book Whale Falls: An exploration of belief and its consequences, I discovered the only other animals on this planet who seem to have brains as complex as ours and which have developed syntactical language are the dolphins and whales – all primarily carnivores. I would note that the animals we tend to cherish as pets are also carnivores or omnivores and even chickens, which some Ashevillians hold dear, love nothing better than frogs. At least that was my experience when I had free range chickens and lived near a swamp.
So we kill to live. Beyond that the dietary discussion is reduced to where we draw our lines. As I described in Whale Falls, cultural decisions fall all over the map. Catholics weren’t allowed to eat meat on Fridays so they served fish, while some Native American cultures held a proscription against eating fish at all. In China cats are a normal dietary item and in Japan they eat whales. One mideastern religion abjures lettuce and rain forest tribes tend to eat a lot of insects. There is very little meat below the forest canopy in rainforests so they invented blow guns and occasionally bring down a monkey. Neanderthals didn’t 
understand that fish were edible and our direct ancestors apparently ate Neanderthals.
Some Jews don’t eat pork, others don’t eat shellfish and some keep strict Kosher – separate containers and serving ware for different foods
Another dietary argument repeatedly offered in favor of veganism involves health. It is plausibly argued that eating meat contributes to heart disease and stroke, and less plausibly to a long list of other ill effects. The problem with this view is first that it assumes good health is everyone’s highest goal, and it demonstrably is not. People do all kinds of things that are more or less likely to shorten their lives. On the flip side, while personal experience is hard to generalize, I know that when we became vegan my then-partner was going through menopause. We ate a lot of soy products. Before she died of estrogen positive breast cancer one line of research I read indicated that her high intake of soy estrogen might very well have accelerated her very aggressive cancer. Would she have survived if we hadn’t become vegans at the wrong time in her life? There’s no way to know.
Priestly celibacy comes to mind
Personally I favor appalled at the horrible conditions and practices that are often justified in the name of commerce. But I have come to accept that my living requires dying and I am comfortable with my decision to eat meat.
I fully understand that those who choose to attempt veganism are well intended, but when it is held out as a form of moral superiority I get very uncomfortable. I’m embarrassed today by the holier than thou attitude I somewhat embraced during my vegan years, laying a head trip on people who didn’t share in my purity. I am way over myself as an authority figure. A lot of true believers seem to fall into that trap, and it’s probably even easier for those who give up something they like: Hey, I’m suffering for this moral superiority, unlike you sinners.