What is needed to keep persons with multiple sclerosis vitamin D-sufficient throughout the year?

Vitamin D sufficiency has been associated with lower risk of multiple sclerosis and may also have a favorable effect on the course of the disease. The aim of this work was to identify predictors of serum 25-hydroxy vitamin D (25[OH]D) levels in persons with multiple sclerosis (MS) and to assess the effect of high-dose vitamin D₃ supplementation on vitamin D status. A 96-week randomized controlled trial was performed to assess the effect of supplementation with 20,000 IU of vitamin D₃ weekly on bone mineral density in 68 patients. We collected data on vitamin D intake and UV-exposure and repeatedly measured serum 25(OH)D levels. Half of the participants had sufficient winter vitamin D levels at baseline (≥50 nmol/l). Vitamin D status was predicted by sun exposure during the last 3 months and by ingested vitamin D from diet and supplements. In the placebo group, the proportion of the participants with sufficient levels increased from 55 % in winter to 92 % during the summer. In the intervention group, all participants had winter 25(OH)D levels above 50 nmol/l at the end of the study. MS patients who have no sun exposure and low dietary vitamin D intake during the winter months should be recommended to take vitamin D supplements to achieve serum 25(OH)D levels of at least 50 nmol/l.