Vitamin D May Lower Risk of Multiple Sclerosis in Whites
Those with highest levels of sunshine vitamin have lower rates of MS, finds study
WEDNESDAY, Dec. 20, 2006 (HealthDay News) -- Could getting some extra sunshine help prevent the development of multiple sclerosis?
Maybe, according to new research that found white people with high circulating levels of vitamin D -- a vitamin mainly produced by the body after sun exposure -- had a lower risk of developing multiple sclerosis (MS). No such association was found for blacks or Hispanics in this study, which is published in the Dec. 20 issue of the Journal of the American Medical Association .
"The group [of whites] with the highest vitamin D levels had a 62 percent decreased risk compared to the group with the lowest levels," said the study's lead author, Dr. Alberto Ascherio, an associate professor of nutrition and epidemiology at the Harvard School of Public Health in Boston.
However, Ascherio cautioned that it was too soon to recommend that anyone -- even those at high risk of developing MS -- start taking vitamin D supplements or increasing their sun exposure with the hope of preventing MS.
Multiple sclerosis is a disease of the central nervous system. It's believed to be an autoimmune disease that causes the body's immune system to attack the substance -- myelin -- that covers nerve cells. About 400,000 Americans have MS, according to the National Multiple Sclerosis Society.
Symptoms of the disorder include poor coordination, loss of balance, blurred vision, fatigue, cognitive problems, numbness and possible paralysis.
Using blood samples stored among a repository of more than 7 million samples maintained by the U.S. Department of Defense, the researchers compared blood samples of 257 people with multiple sclerosis to 514 age, sex and race-matched control samples.
One hundred forty eight of the samples were from whites; 77 were from blacks, and 32 were from Hispanic adults.
The researchers analyzed the blood samples for levels of circulating vitamin D and separated the samples into five groups based on the vitamin D levels.
They found that the group with the highest levels had a 62 percent decreased risk of MS compared to the group with the lowest.
However, these differences only held true for white people. There was no association for blacks and Hispanics. The researchers theorized that may be either because the sample sizes were much smaller than they were for whites or because blacks and Hispanics have lower levels of circulating vitamin D.
Ascherio said the researchers don't know for sure whether vitamin D may play a role in causing MS, but they suspect that it probably does.
"There is a pretty good convergence of evidence that vitamin D affects the immune system to lower the risk of MS," he said, adding that if that is the case, "the potential for prevention is enormous."
"This is another piece of the puzzle, and it may help to explain why we see geographic difference in MS," said Dr. Nicholas LaRocca, associate vice president of health care delivery and policy research at the National Multiple Sclerosis Society.
But what this association means -- "is it an actual risk factor; how does it work; what can we do about it?" -- is open to question, he added.
"In the future, if one could establish a causal relationship, it could present an opportunity for a partially preventive strategy. Right now, the scientific community is not convinced that there's enough evidence to recommend taking vitamin D supplements, though," LaRocca said.
To learn more about multiple sclerosis, visit the National Multiple Sclerosis Society.