When pulling out one of my old Nursing Text books from about 20 years ago, there is not even a listing on vitamin D. A is there, so is C and lets not forget E. But no D.
Well, the frontiers of knowledge are exploding on vitamin D. In addition to helping your body boost glutathione (which helps prevent cancer) it has a dark side that most do not know about.
If you like to suntan, pay attention. You will love this. Vitamin D helps you tan faster.
But be careful. You can overdose on it and especially the synthetic kind. The second best source for vitamin D would be fish oils. Taking supplements could actually help prevent skin cancer during the tanning months and help you to tan faster.
Good health to you.