A team in Israel held a study of 60 chronic pain sufferers, mainly those with fibromyalgia as well as some with osteoarthritis and rheumatoid arthritis. All the patients sun-bathed briefly each day for three weeks under strict medical supervision. All their pain levels, disease severity, and serum vitamin D were measured before and after the three week period.
After the three weeks vitamin D was shown to be increased by 25%.
What the team found out was that regular sun exposure causes your skin to produce vitamin D, it can also soothe sore muscles and bring on relaxation and also may reduce fibromyalgia pain.
Vitamin D is known for its immune system effects on relieving pain and inflammation so in theory by making sure you get adequate sun should lead to greater vitamin D levels and maybe less fibromyalgia pain.
As a fibromyalgia sufferer myself I have to say that I have less pain while I am away in a sunny climate which I always put down to the higher temperatures but fibromyalgia sufferers also notice massive changes in pain during the change of seasons.