According to an extensive review of clinical research in a report from Pain Treatment Topics (http://Pain-Topics.org), inadequate vitamin D has been linked to a long list of painful maladies, including bone and joint pain, muscle aches, fibromyalgia syndrome, rheumatic disorders, osteoarthritis, and other complaints. Lack of vitamin D also has been implicated in the mood disturbances of chronic fatigue syndrome and seasonal affective disorder, or SAD, which are more common during winter.
"In our review of 22 clinical research studies persons with various pain and fatigue syndromes almost always lacked vitamin D, especially during winter months. When sufficient vitamin D supplementation was provided, the aches, pains, weakness, and related problems in most sufferers either vanished or were at least helped to a significant degree."
-Author of the report and editor of Pain Treatment Topics, Stewart B. Leavitt, MA, PhD
MY COMMENT: Rather than fooling around with individual supplements, I suggest runners take a good quality antioxidant that gives you everything you need. I use LifePak Nano by Pharmanex- not cheap but I am confident that endurance athetes require optimal protection against free radical damage, and Pharmanex has the only product that actually demonstrates results (Biophotonic Scanner). When I started taking LifePak, my skin carotenoid score was 36,000. After 3 months on the supplement my score went as high as 80,000!