Effect of vitamin D3 supplementation on relapses, disease progression, and measures of function in persons with multiple sclerosis: exploratory outcomes from a double-blind randomised controlled trial

Background: High vitamin D levels may reduce the risk of relapses and disease progression in multiple sclerosis. Methods: This 96-week randomised controlled trial was designed to assess the effect of vitamin D-3 supplementation on bone mineral density in persons with multiple sclerosis. Supplementation with 20,000 IU vitamin D-3 weekly raised median serum 25-hydroxy vitamin D (25[OH]D) to 121 nmol/L. The modified intention to treat analysis included 35 persons in the vitamin D-3 group and 33 in the placebo group. Participants were age 21 to 50 years and fully ambulatory (median Expanded Disability Status Scale (EDSS) 2.5). We studied the effect of supplementing vitamin D-3 on the exploratory outcomes annualised relapse rate (ARR), EDSS, multiple sclerosis functional composite (MSFC) components, grip strength, and fatigue. Results: After 96 weeks, there was no significant difference between groups in ARR (absolute difference 0.10, 95% CI -0.07 to 0.27; p = 0.25), EDSS (absolute difference -0.01, 95% CI -0.35 to 0.35; p = 0.97), MSFC components, grip strength, or fatigue. Conclusion: Supplementation with 20,000 IU vitamin D-3 weekly did not result in beneficial effects on the measured multiple sclerosis-related outcomes. This study was not powered to address clinical outcomes, but none of the results were suggestive of an effect in this unselected population of fully ambulatory persons with multiple sclerosis.