Low vitamin D status has been implicated in the etiology of autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, insulin-dependent diabetes mellitus, and inflammatory bowel disease.

The optimal level of vitamin D intake required to support optimal immune function is not known but is likely to be at least that required for healthy bones.

Experimentally, vitamin D deficiency results in the increased incidence of autoimmune disease.

Mechanistically, the data point to a role for vitamin D in the development of self-tolerance.

The vitamin D hormone (1,25-dihydroxy vitamin D(3)) regulates T helper cell (Th1) and dendritic cell function while inducing regulatory T-cell function. The net result is a decrease in the Th1-driven autoimmune response and decreased severity of symptoms.

This review discusses the accumulating evidence pointing to a link between vitamin D and autoimmunity. Increased vitamin D intakes might decrease the incidence and severity of autoimmune diseases and the rate of bone fracture.

PMID: 15564440

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