Vitamin D for the treatment of multiple sclerosis: a meta-analysis.

OBJECTIVE There is an association between latitude, relative vitamin D deficiency and risk of multiple sclerosis (MS), and an association between vitamin D and disease progression. We have performed a meta-analysis with the aim of investigating the role of therapeutic vitamin D in MS. METHODS A systematic search of databases was performed to identify clinical trials assessing vitamin D in patients with relapsing-remitting MS. Studies were selected based on inclusion and exclusion criteria. Analysis was performed using RevMan 5.3 software. RESULTS Twelve studies involving 950 patients were included in the final analysis. Studies were divided into four groups because of heterogeneity in study design. Studies were judged to be at low or unclear risk of bias, except in three studies, and this was confirmed by funnel plots. No statistically significant difference was seen for any of the outcome measures. There were non-significant trends in favour of vitamin D for all outcome measures, particularly when only placebo-controlled studies were included. Dose comparison studies showed a significant increase in annualised relapse rate (mean difference 0.15 [95%CI 0.01-0.30]) and non-significant trends of increased Expanded Disability Status Scale and gadolinium-enhancing lesions for the higher-dose arms. CONCLUSION These findings suggest that vitamin D supplementation may have a therapeutic role in the treatment of MS. However, there is uncertainty with regard to the most appropriate dose, with high doses potentially being associated with worse outcomes. There remains the need for further well-performed randomised, dose-ranging, placebo-controlled trials of vitamin D in MS.