Can Low Vitamin D Cause Autoimmune Diseases?

Vitamin D, which is sometimes called "the sunshine vitamin," has long been recognized as an important participant in calcium metabolism. The classic vitamin D-deficiency disease called rickets is characterized by soft, poorly formed bones. However, vitamin D's additional role in immunity has emerged as a focal point for scientists during the past three decades. In particular, an increasing body of evidence points to vitamin D deficiency as a potential cause of autoimmune diseases, such as multiple sclerosis, type 1 diabetes and Crohn's disease.

Receptors

In December 1979, scientists reporting in the journal "Lancet" announced the discovery of specific receptors for activated vitamin D in cells from breast cancer. Subsequently, multiple studies revealed the presence of vitamin D receptors, or VDRs, on many normal cells, too, and it is now known that nearly every cell in your body possesses these receptors. Although the precise actions of VDRs in many tissues are unclear, those in your immune cells appear to exert a great deal of influence on how you respond to various immune threats. More importantly, a lack of VDR stimulation due to vitamin D deficiency has been linked to exaggerated or inappropriate immune responses that characterize autoimmune illnesses.

Multiple Sclerosis

Multiple sclerosis, or MS, is a chronic inflammatory disease of your nervous system that is believed to arise from autoimmune destruction of myelin, the protective sheath that surrounds your nerves. In the October 2008 issue of the "Journal of Cellular Biochemistry," scientists cited a relationship between a lack of sun exposure -- hence, vitamin D deficiency -- and a higher incidence of MS at higher latitudes. They also linked low vitamin D levels to immune hyperactivity that coincides with the development of MS.

Type 1 Diabetes

According to Dr. Martin Hewison at the David Geffen School of Medicine in Los Angeles, the increased incidence of type 1 diabetes among vitamin D-deficient individuals mirrors that of multiple sclerosis. Adolescents diagnosed with type 1 diabetes frequently have low vitamin D levels, and animal models of type 1 diabetes exhibit increased disease severity when they are deprived of vitamin D. Furthermore, certain VDR subtypes that are more sensitive to vitamin D stimulation appear to offer protection against type 1 diabetes in humans.

Crohn's Disease

Inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis, are triggered by inappropriate immune responses that damage the wall of your gastrointestinal tract. An October 2008 review in the "Journal of Cellular Biochemistry" reported that vitamin D deficiency is relatively common among sufferers of Crohn's disease. In addition, animal studies have demonstrated a link between low vitamin D levels and inflammatory bowel disorders. The review's author speculated that vitamin D deficiency impairs the activity of some portions of your immune system that protect you from autoimmune diseases while simultaneously allowing inflammatory responses to occur in other portions.

Considerations and Recommendations

Vitamin D deficiency has been linked to a number of autoimmune diseases. The exact relationship between low vitamin D levels and autoimmunity has not yet been defined, but it is mediated by specific receptors in your immune cells and other tissues. Vitamin D deficiency is fairly common among some populations, and these groups may be more susceptible to specific diseases, such as multiple sclerosis. Recommended dietary allowances for vitamin D -- the doses that prevent deficiency -- vary from 400 IU daily for infants to 800 IU for adults over 70. Ask your doctor if you are meeting your vitamin D needs.