I often wonder if true vegans really do survive in optimum health, since humans are designed to eat a variety of things, including animals. However, all nutrients can be had on a vegan diet, altho I personally would suppliment if I were eating that way.
I know vegans and vegetarians who look far younger than their years and they do take supplements. They normally eat only organic (many of them from their own gardens in the summer) and get a lot of exercise as well.