I am not sure if I agree that veganism is completely superior from a health aspect. I think it depends on the individual. Many (most?) people can go vegan and feel great if they make an effort to find alternate sources of protein, etc. Humans evolved as carnivores over millennia; I would be surprised if evolution would select for such a costly trait unless it was providing some health benefit for that particular species.

One friend of mine had a terrible paradox. She had recently taken precepts as part of converting to Zen Buddhism and her personal interpretation was that she should become a vegan to facilitate this.

After about 18 months, she had to quit and go back to a diet with meat and dairy because her health was deteriorating visibly and rapidly. She spoke with her teacher (and doctor) about this at great length and the teacher told her that while it is noble to become a vegan to reduce suffering in the world, one should not try to reduce suffering in ways that increase your own suffering. She tried all sorts of ways to stay vegan including tons of supplements, careful nutrition, and so on. For whatever reason, her body does not function well in a vegan state. I think this is the exception rather than the rule, but people with absorption problems, etc. need to be more careful when switching to a vegan diet.