Is hypovitaminosis D associated with fibromyalgia? A systematic review.

Context: Recent findings have suggested a high prevalence of vitamin D deficiency or insufficiency in fibromyalgia (FM) patients despite the lack of clinical and pathophysiological evidence.

Objective: A systematic review was conducted to examine the association between vitamin D status and FM, including the effect of vitamin D supplementation. Data source: PubMed, LILACS, Scopus, SciELO, Cochrane, and EMBASE were searched, from January 2000 to July 2018, using the descriptors "Fibromyalgia" and "Vitamin D." Study selection: Trials including FM patients in whom vitamin D levels were assessed were eligible for inclusion. Data extraction: Data comprised age, gender, country, aims, bias, diagnosis criteria, cutoff point, and status of vitamin D, together with FM symptoms and vitamin D supplementation protocol.

Results: A total of 26 articles were selected. Most of the studies were found to present unreliable control groups and small samples. Experimental data on vitamin D supplementation indicated improvement in certain FM symptoms.

Conclusion: Prevalence of hypovitaminosis D in the FM population and the cause-effect relationship were inconclusive. Nevertheless, vitamin D supplementation may be considered as a co-adjuvant in FM therapy.