Vitamin D and Chronic Pain: A Comprehensive Review

Abstract

In recent years vitamin D has gained popularity in the media, on the internet, and throughout alternative treatment practitioners as a cheap and effective option to treat many diseases. Research showing that vitamin D receptors are present in virtually all cells of the body, and the increasing data demonstrating a relationship of vitamin D metabolites to chronic diseases, have led to widespread treatment of medical conditions with vitamin D supplementation. Chronic pain and inflammatory conditions are increasingly linked to vitamin D deficiency. The question posed in this review is whether there is significant, quality research to recommend vitamin D supplementation for patients with chronic pain conditions. Utilizing publications from PubMed for the review, various search terms were entered for vitamin D (vitamin D; vitamin D2; vitamin D3; 1,25-dihydroxyvitamin D3; 1,25-dihydroxycholecalciferol; 25 hydroxycholecalciferol; 25-hydroxyvitamin D; alfacalcidol; calcidiol; calcitriol; calcifediol; calciferol; ergocalciferal; cholecalciferol); and "pain." The search was continued from the last day of the Straub et. al. review, September 8th, 2008. The last search was conducted on December 5, 2012. The search protocol from Straub et. al was followed as well. Also, added to this search protocol were the terms: vitamin D receptor; VDR and "pain." These terms enabled a search for genetic links between vitamin D and pain. The search criteria resulted in nine relevant articles (from the original 1,069 studies) with varying treatment protocols in each article making any statistical representation impossible. Results on the effectiveness of vitamin D correlation with chronic pain were extremely variable, with most papers drawing the conclusion that more quality research needs to be implemented on the subject. Due to the variability and lack of quality randomized controlled trials, the current literature can only suggest a possible link between vitamin D levels and pain. Also, recent research into Vitamin D Receptors (VDR) has opened up a possible connection between VDR polymorphisms and pain. So, after a comprehensive review of vitamin D, Vitamin D Receptors, and pain, there is still not enough evidence to recommend supplementation to treat chronic pain conditions. However, enough evidence is available to recommend future high quality, randomized controlled trials to help determine the influence vitamin D and VDRs have on pain issues.