There is now so much evidence of the harm caused by flesh foods due to lack of fibre and high content of saturated fat, that vegetarianism is gaining widespread popularity for health reasons. During the two World Wars, countries whose peoples changed to vegetarian diets showed a marked improvement in general health and a significant drop in heart disease. When the diet is based on flesh foods, the dominant gut bacteria are putrefactive, and toxins, such as ammonium compounds, are produced. With a meat diet the natural synthesis of vitamin B12 in the gut is inhibited and the person can become dependent on B12 from animal sources. Animal fats lining the gut may interfere with digestion and absorption of calcium and other water-soluble minerals.
Meat is little more than second-hand grass.
We need our nutrients first-hand. We do better if we eat entirely or almost entirely from the plant kingdom. However, after a lifetime of meat-eating, changing to vegetarian usually needs to be made gradually and perhaps with professional supervision. It is very close to that of our cousins, the mainly-vegetarian apes including gorillas. There is no doubt that our bodies are designed to handle diets that are basically vegetarian.