Interesting article from PJmedia on Vitamin D.
What prompted the scientist to check out the importance of Vitamin D?
When I asked Holick what the source of his epiphany was so long ago, he explained that it was the simple fact that D is a critical nutrient without a natural food source. It is so important biologically that early humans could manufacture D even during famines.
If humans needed something to live in the past, logically they need it now.
Go out and get some sunshine.