Efficacy and safety of weekly vitamin D in patients with fibromyalgia: 12-week, double-blind, randomized, controlled placebo trial.

Introduction: FM is a chronic musculoskeletal disorder characterized by the presence of generalized pain. There are contradictory results regarding the prevalence and supplementation effect of vitamin D deficiency on FM patients. We aim to determine the safety and efficacy of a 12-week vitamin D supplementation on FM patients.

Methods: We conducted a randomized, placebo-controlled, double-blind clinical trial. We included female participants of 18 years old or older, who met 1990 or 2010 ACR criteria for fibromyalgia. The Spanish validated FIQ and the VAS of pain were applied at baseline. The participants were then randomized to receive placebo or 50,000 IU of Vitamin D PO, weekly for 12 weeks.

Results: We included 80 patients. There was no statistical difference in the initial and final FIQ between both groups. The FIQ delta also did not prove to be different at the end of the study. The increase in vitamin D levels in the intervention group was corroborated. Regarding serious adverse effects, none was reported in both groups. There was no statistical difference in minor adverse events.

Conclusion: In this double-blind placebo-controlled randomized study conducted to measure the efficacy and safety of vitamin D exclusively in patients with FM, we found that there is no evidence of a trend in favor of vitamin D treatment, since we did not observe improvement in the VAS of pain or FIQ.

Trial Registry: Clinical Trials.gov number: NCT03369379 Key Points • There are conflicting results in vitamin D to treat fibromyalgia. • In this double-blind, randomized controlled trial, we did not find a difference in the VAS nor FIQ with vitamin D supplementation. • The increase in vitamin D levels in the intervention group was corroborated.