Objectives There is an association between latitude, relative vitamin D deficiency and risk of multiple sclerosis (MS). There is some evidence for an association between vitamin D and disease progression. Many neurologists recommend vitamin D supplementation for MS. A number of small trials of vitamin D have been undertaken. We have performed a meta-analysis with the aim of investigating the role of therapeutic vitamin D in relapsing-remitting MS.

Methods A systematic search of databases was performed to identify clinical trials assessing vitamin D in patients with relapsing-remitting MS. Articles were screened independently by two investigators and trials were selected based on inclusion and exclusion criteria. Analysis was performed using RevMan software.

Results Seven studies involving 284 patients were included in the final analysis. All studies involved the use of vitamin D as add-on therapy. Studies were divided into two groups for analysis to improve homogeneity of outcomes: vitamin D dosing versus placebo and high versus low dosing protocols. Results for studies were judged to be at low risk of bias and this was confirmed by funnel plots. A statistically significant reduction of GAD-enhancing lesions (mean difference −0.98 (95% CI −1.79 to 0.18)) was seen in placebo-controlled studies. There were non-significant trend towards fewer relapses and improvement in EDSS for these studies. Dose comparison studies showed a significant increase in EDSS (mead difference 0.4 (95%CI 0.36 to 0.44)) and non-significant trends of increased annualised relapse rates and GAD-enhancing lesions for the higher dose arms.

Conclusions These findings suggest vitamin D supplementation may have a therapeutic role in the treatment of MS. However, there is uncertainty with regards to the most appropriate dose, with higher dose potentially being associated with worse outcomes. There remains the need for a well performed randomised, dose-comparison, placebo-controlled trial of vitamin D in MS.