I've been reading a lot about vitamin D lately.  What are the benefits, and how can I make sure I'm getting a sufficient amount?
D000368:Aged; D001842:Bone and Bones / Q000187:drug effects; D006801:Humans; D008875:Middle Aged; D009751:Nutritional Requirements; D014807:Vitamin D / Q000008:administration & dosage*
D014807:Vitamin D