We now have a wiki!
Yes, it's the best source of vitamin D. I posted this previously in the vitamin D thread under "Vitamins", but I'll post it here too. It's a vitamin D by sun calculator:http://nadir.nilu.no/~olaeng/fastrt/VitD-ez_quartMED.html
Half an hour, completely naked, in the sun, at the equator (best case scenario) produces 10000IU of vitamin D.
I've mentioned this once before, but it bears repeating:Be careful with RDA numbers. Some are very low, the smallest number of item X needed to avoid Y serious affliction and make a man fit for army service.Translation: there is often a HUGE gap between bare minimum and optimal