Vitamin D may help lower MS risk

Scientists had long been assuming that vitamin D has the potentiality to lower the chance of developing multiple sclerosis (MS), but they had no adequate evidence to turn their assumption into reality.

Now, researchers at the Harvard School of Public Health (HSPH) have figured out a relationship between vitamin D levels and MS, an incurable disease of the central nervous system.

In their research, the first large-scale, prospective study to probe the link between vitamin D and the neurological disease, the scientists found that an abundance of vitamin D in the blood may lower the risk of multiple sclerosis.

"We established with a certain degree of confidence that people with high vitamin D levels have a lower risk of developing MS. What we don't know for sure if increasing their vitamin D levels will actually prevent MS," said Dr. Alberto Ascherio, senior author of the study and associate professor of nutrition and epidemiology at HSPH.

In their study, Dr. Ascherio and his fellow scientists involved U.S. Army and Navy personnel who had blood samples stored in the Department of Defense Serum Repository. Of more than seven million military personnel, the team finally concentrated on 257 U.S. Army and Navy personnel with at least two serum samples stored in the repository, and were diagnosed with MS.

As vitamin D levels are strongly influenced by skin color, the researchers analyzed all the races including whites, blacks, and Hispanics separately and divided the study subjects into five groups of equal size according to their average levels.

After comparing the levels of 25-hydroxyvitamin D, a good indicator of vitamin D availability to tissues, in selected blood serum samples of study groups, the researchers discovered that of white personnel, who have the highest vitamin D levels are at the lower risk of developing MS, while among those, who have the lowest vitamin D levels, the risk of developing the disease is highest.

Researchers found that among whites, there was a 41% decrease in MS risk for every 50 nanomoles per litre increase in 25-hydroxyvitamin D. Those with the highest blood levels of vitamin D (in the top 20%) had a 62% lower risk of developing the disease than those whose level was in the bottom 20%.

The team found no such association between blood levels of vitamin D and MS in blacks or Hispanics, possibly because the researchers had the smaller size of these sample groups.

Although the study, which appear in the December 20, 2006, issue of the Journal of the American Medical Association, is very much encouraging but did not provide proof yet that vitamin D will protect humans from this disease.

Multiple sclerosis, the chronic autoimmune disease, affects some 350,000 people in the U.S. annually and nearly2 million worldwide. The disease is more common among women than men and occurs most commonly in young adults.

"Our findings suggest that vitamin D may have a direct impact on MS risk," said Ascherio. "If we confirm that the vitamin is protective, we could potentially prevent thousands of cases of MS a year in the United States alone."

A large, tightly controlled study is needed before doctors suggested taking vitamin D supplements to stave off MS, he said.