The first large-scale study that examines the association between circulating vitamin D and multiple sclerosis (MS) predicts a lower risk of this neuropathy in individuals having a high serum concentration of vitamin D. The study was published in the Dec. 20, 2006, issue of the Journal of the American Medical Association and conducted by Kassandra Munger, a doctoral student in nutrition, and Alberto Ascherio, HSPH associate professor of nutrition and epidemiology.
The research was done in collaboration with the U.S. military, which provided access to serum samples of 7 million active-duty military personnel collected since 1990. The investigators identified 257 cases of MS occurring among Army and Navy personnel between 1992 and 2004.
Previous studies that have attempted to address the link between vitamin D and MS risk have either been retrospective and have relied largely on patient history to determine early-life exposure to sunlight, and therefore vitamin D, a method that is open to erroneous information, or focused only on dietary intake of vitamin D. In the present prospective study, the researchers measured serum concentrations of 25-hydroxyvitamin D, a good indicator of vitamin D availability to tissues, in two or more serum samples from each of the MS patients collected over a course of a few years prior to their MS onset and in controls who were drawn randomly from the population. The data obtained were analyzed to assess risk of MS as a function of serum vitamin D levels.
This study found that, among whites, those in the top 20 percent of vitamin D levels (>99.1 nmol/L) had a 62 percent lower risk of MS compared to individuals with levels in the bottom 20 percent (<63.3 nmol/L). The association was strongest in whites less than 20 years old. A similar association was absent in African-American and Hispanic populations, likely due to smaller sample sizes and intrinsic lower levels of vitamin D in these populations.
An extension of this research will involve charting a dose–response curve to assess levels of vitamin D required to confer protection against MS. Such a study could pave the way for broad intervention strategies to lower the risk of disease in susceptible populations.
