For release: Wednesday, January 31, 2007
A new study shows that multiple sclerosis (MS) is linked to low levels of vitamin D in the blood, but it’s unclear whether vitamin D deficiency is a causal factor in the disease or whether vitamin D supplements would protect against it.
Alberto Ascherio, M.D., Dr.P.H., a professor of nutrition and epidemiology at the Harvard School of Public Health in Boston, examined the connection between vitamin D and MS by accessing medical records and blood samples from more than 7 million U.S. military personnel. He found that in some soldiers with MS, vitamin D levels in the blood – drawn as a routine matter several years before they were diagnosed – were lower than in soldiers without the disease. The study was supported by the National Institute of Neurological Disorders and Stroke (NINDS), and appeared in the December 20, 2006 issue of the Journal of the American Medical Association.*
MS occurs when the body’s own immune system attacks the protective sheath around axons – the tendril-like extensions that connect nerve cells. It typically appears between the ages of 20 and 40, causing weakness in the extremities and problems with coordination, and it may progress to partial or complete paralysis. The cause of the disease is unknown, but genetic predisposition and environmental factors both play some role.
Vitamin D is produced within the body, in response to sunlight on the skin. Very little of the vitamin is derived from food, but it can be ingested. In a 2004 study involving nearly 200,000 women, Dr. Ascherio found that use of vitamin D supplements over a 10- to 20‑year span was correlated with a low risk of MS.
In the new study, Dr. Ascherio and his team searched through personnel files kept by the Department of Defense, and identified 315 service members who had a definite or probable diagnosis of MS plus at least one serum (blood) sample taken before diagnosis. In some cases, the serum sample had been taken more than 10 years before diagnosis. The serum level of vitamin D in each person with MS was compared to the level in two control subjects who didn’t have the disease, but were otherwise matched on the basis of age, sex, race, serum collection date, and branch of the military. To account for the effect of sunlight on vitamin D, the latitude of each service member’s residence at the time of enlistment also was factored into the analysis.
When white subjects were ranked into five roughly equal-sized groups based on their vitamin D levels, those with MS fell disproportionately into the lowest-ranking groups. From the highest to the lowest-ranking group, the likelihood of having MS increased by 62 percent. There was no correlation between vitamin D levels and MS in black or Hispanic subjects.
In whites with MS, the fact that vitamin D levels were down years before diagnosis suggests that low vitamin D is a contributing factor, rather than merely a consequence in the disease, Dr. Ascherio said. Still, a definitive answer requires further research, he said.
“The question is whether individuals who are at high risk of MS [for example, because they have an affected relative] could reduce the risk by taking vitamin D,” he said. At this point, it remains uncertain whether vitamin D can protect against or ameliorate MS, he said.
*Munger KL, Levin LI, Hollis BW, Howard NS, Ascherio A. “Serum 25-Hydroxyvitamin D Levels and Risk of Multiple Sclerosis.” Journal of the American Medical Association, December 20, 2006, Vol. 296(23), pp. 2832-2838.
-By Daniel Stimson, Ph.D.
Last Modified June 8, 2009