Vegetarianism vs. factory meat-farming? We have lost our instincts about what is natural to eat. No other animal has philosophical discussions about the subject. Choosing a diet based on ideology can get you in big trouble if your ideology doesn't match your biology.
What do humans eat naturally? Our teeth are like chimpanzees' — chimps are largely herbivorous, but occasionally kill and eat small animals. We now know gorillas also eat small amounts of animal food, but mostly leaves and shoots, needing to eat almost constantly, with a bony skull-crest anchoring their huge jaw muscles.
Anthropologist Louis Leakey thought that humans evolved because we ate meat and used fire. Cooked (partially predigested) meat and vegetables allowed eating less, chewing less. The bony crest disappeared, letting our brain expand. Before we were human, we stood up and chased our prey with spears.
All "primitive" cultures ate some meat, if only a little. Agriculture built ancient civilizations, with grains the staple food source, but meat was welcomed when available. Traditional Chinese medicine has 2,000 years of scientific experience with the energetics of food and human health, recommending cooked vegetables and grains as the bulk of the diet, with smaller amounts of meat and other foods, such as fruits, nuts and raw vegetables, as supplements. Three ounces of meat per day is enough. It makes biological and ethical sense. Buy from local producers. If you choose a vegan diet, you need three cups of cooked beans to get the same amount of protein; and eat fermented foods and take care of your intestinal flora to avoid B-12 deficiency. Feel a little spacy and crave sweets? You are probably protein deficient.
If you can get around your ideology, have a little animal food when your body asks for it. It's your biology talking.
— Kim Bonsteel