We can't all be in Cape Cod in the middle of summer at high noon, naked to get 20,000 IU's in 20 minutes, so we take vitamin D.
It helps fibromyalgia, peripheral neuropathy,and a host of other ills.
Copious and exacting studies on Vitamin D are available. Google and then Just Do It! GET YOUR VitD!
Here, just check it out.