The incidence of multiple sclerosis (MS) is significantly greater in higher latitudes, whether north or south of the equator. This striking fact has lead researchers to investigate if the lower exposure to ultraviolet light from sun exposure in these latitudes, and a resultant seasonal vitamin D deficiency, contributes to the higher risk of MS. In a recent issue of the Journal of The American Medical Association (JAMA), researchers reported "high circulating levels of vitamin D are associated with a lower risk of multiple sclerosis."
Researchers from the Harvard School of Public Health, Walter Reed Army Institute of Research, and others examined serum vitamin D levels in 257 MS cases and 514 controls, all of who were Army or Navy personnel. They found a significant protective effect of higher blood levels of 25-hydroxyvitamin D levels, including a 51-percent reduction in incidence of MS in individuals with blood levels of 100 nmol/L or higher. The researchers did not find any African-American patients or controls with levels this high, and thus they found no protective effect of higher vitamin D levels in these participants, or in Hispanics involved in the study.
Exposure to UV rays from sunlight and the subsequent biochemical production of vitamin D in the body is the primary source of vitamin D in humans. People with darker skin tone are more protected from sunburn because of the higher melanin content of their skin; however, they also create less vitamin D and thus have lower levels of this nutrient that is essential for bone density and immune function.
This study is a prospective study; i.e., one that examines a correlation between a nutrient and a disease and therefore cannot determine causality. But with the totality of the recent research on vitamin D, it appears moderate sun exposure and/or supplementation with vitamin D can improve one's risk for MS.
Munger KL, Levin LI, Hollis BW, et al. Serum 25-hydroxyvitamin D levels and risk of multiple sclerosis. JAMA 2006(23):2832-2838.
