A pilot study of the immunological effects of high-dose vitamin D in healthy volunteers.

Although vitamin D deficiency is considered an environmental factor in multiple sclerosis (MS), the immunological and clinical effects of vitamin D supplementation remain unclear. We performed a pilot study of the immunomodulatory effects of vitamin D in healthy individuals (n=4), who took 5000-10,000 IU/day of vitamin D over 15 weeks. After 15 weeks of vitamin D supplementation, serum 25(OH) vitamin D levels rose significantly from baseline, with a corresponding increase in IL-10 production by peripheral blood mononuclear cells and a reduced frequency of Th17 cells. These data provide a strong rationale for randomised trials to assess the clinical effects of vitamin D supplementation in MS.