Clinical question Is vitamin D supplementation effective in the treatment of chronic pain in patients with normal serum levels or low serum levels?
Bottom line The currently available evidence does not demonstrate a relationship between low vitamin D levels and chronic pain. As in many interventions in medicine, unmasked trials and case series show a benefit of vitamin D supplementation that is not subsequently verified by masked, controlled trials. (Level of evidence = 3a)
Synopsis Though lacking a plausible mechanism, vitamin D deficiency has been associated with pain caused by osteomalacia and other causes of chronic pain. The researchers conducting this less-than-rigorous systematic review attempted to summarize the support for this theory. They searched medline (but no other databases) for research on the relationship between vitamin D and pain, as well as bibliographies of review articles, including trials in any language. They give no other details on the conduct of their research protocol. Five randomized double-blind trials assessed the effectiveness of vitamin D treatment in a total of 229 patients; only one study of 22 patients found a benefit of vitamin D supplementation on “pain-mobility scores” in postmenopausal women with backache. Only one study enrolled patients with pain and vitamin D deficiency, and this study showed no benefit following 3 months of treatment. Lower quality studies—case series—showed a benefit of treatment. Low vitamin D levels were no more common in patients with chronic pain than in control populations, regardless of latitude (and likely sunlight exposure).
Straube S, Andrew Moore R, Derry S, McQuay HJ. Vitamin D and chronic pain. Pain. 2009;141(1-2):10-13.