Research suggests depressed levels of vitamin D important to body’s immune system

THOUSAND OAKS, Calif. Deficiency in vitamin D has been widely regarded as contributing to autoimmune disease, but a review appearing in Autoimmunity Reviews released Wednesday counters that low levels of vitamin D in patients with autoimmune disease may be a result, rather than a cause of disease, and that supplementing with vitamin D may actually exacerbate autoimmune disease.

Authored by a team of researchers at the California-based non-profit Autoimmunity Research Foundation, the paper suggests that the form of vitamin D derived from food and supplements, 25-hydroxyvitamin D (25-D), is a secosteroid rather than a vitamin. Like corticosteroid medications, vitamin D may provide short-term relief by lowering inflammation but may make disease symptoms worse over the long-term.

The insights are based on molecular research showing that 25-D inactivates its native receptor - the Vitamin D nuclear receptor or VDR. Once associated solely with calcium metabolism, the VDR has been linked to the control of the immune response by expressing the bulk of the body's antimicrobial peptides, natural antimicrobials that target bacteria.

Low levels of 25-D are frequently noted in patients with autoimmune disease, leading to a consensus that a deficiency of the secosteroid may contribute to the autoimmune disease process. Marshall and team countered that these low levels of 25-D are a result, rather than a cause, of the disease process. Marshall's research suggests that in autoimmune disease, 25-D levels are naturally down-regulated. Under such circumstances, supplementation with extra vitamin D could potentially prove counterproductive, as it slows the ability of the immune system to deal with bacteria.