Recent findings suggest that vitamin D supplementation may have a therapeutic role in the treatment of multiple sclerosis (MS). However, there is uncertainty with regard to the most appropriate dose, with high doses potentially being associated with worse outcomes. 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. 12 studies involving 950 patients were included in the final analysis. Researchers found:

• No statistically significant difference was seen for any of the outcome measures.
• There were non-significant trends in favor of vitamin D for all outcome measures, particularly when only placebo-controlled studies were included.
• Dose comparison studies showed a significant increase in annualized relapse rate (mean difference 0.15) and non-significant trends of increased Expanded Disability Status Scale and gadolinium-enhancing lesions for the higher-dose arms.