Steroids are a common class of organic molecules and don't preclude membership in the group we've labeled "vitamins". Vitamins are a label we give, not on stru

Steroids are a common class of organic molecules and don't preclude membership in the group we've labeled "vitamins". Vitamins are a label we give, not on structure, but on function and our own ability to synthesize them. Vitamin D likely wouldn't be a vitamin were we all still running naked in Africa, but that's mostly not the case.