Purpose of review: The role of vitamin D in situations other than calcium homeostasis and bone health has become very topical. It is apparent that vitamin D has significant effects on the immune system and as such may contribute to the pathogenesis of autoimmune disease. This review examines the evidence-to-date that vitamin D has a role in immune-mediated rheumatic disorders.
Recent findings: Low vitamin D status is reported in many inflammatory rheumatic conditions. In some this extends to an association with disease activity. Vitamin D acts on a number of cells involved in both innate and acquired immunity biasing the adaptive immune system away from Th17 and Th1, towards Th2 and Tregs. Deficiency accordingly could encourage autoimmunity. Direct evidence for this plausible mechanism in specific diseases remains largely to be demonstrated. To date, there is a dearth of controlled trials of vitamin D in prophylaxis or therapy.
Summary: Vitamin D deficiency may well be an important factor in autoimmune rheumatic disease, including initial disease development and worsening the disease once present. This is testable and there is a pressing need for therapeutic studies.