Washington: People with higher levels of vitamin D have a markedly reduced risk of developing multiple sclerosis (MS), according to a study published on Tuesday that may point to a promising way to protect against the disease.
MS is an incurable and often disabling disease of the central nervous system that appears most often among young adults and affects two million people globally.
Researchers at the Harvard School of Public Health in Boston combed a massive repository of serum samples from more than seven million US military personnel to find 257 people who developed MS.
Their samples were analysed for vitamin D levels and compared with a group of randomly picked military personnel from the same broad population who did not develop MS.
Among the white people studied, the chances of developing MS fell as vitamin D levels in the body rose, according to findings published in the Journal of the American Medical Association.
Among whites, the majority of those in the study, the risks of MS fell 62 per cent for those in the top fifth of vitamin D concentration.
The researchers said this suggested that many cases of MS could be prevented if people raised their vitamin D intake.
"This converges with a body of experimental evidence and other studies that strongly suggest that vitamin D could be truly protective," Alberto Ascherio, associate professor of nutrition and epidemiology at Harvard School of Public Health and the lead researcher, said in a telephone interview.
The relationship between higher vitamin D levels and MS risk was absent in the black and Hispanic people in the study, researchers said, perhaps because so few were involved or both groups had overall lower levels of vitamin D than whites.
Ascherio said more research was needed to nail down whether vitamin D leads to a reduced risk of MS.
"If it is true, the implication could be enormous for MS prevention," Ascherio said.
Nicholas LaRocca of the National Multiple Sclerosis Society, an advocacy group that helped fund the study, called the findings promising but said it was premature to recommend that young people take vitamin D supplements to ward off MS.
Vitamin D, a hormone manufactured naturally in the body, promotes the absorption of calcium necessary for developing and maintaining healthy teeth and bones.
Calcium is also important to nerve cells, including the brain, while vitamin D also seems to act as a regulator of the immune system.
The body makes the vitamin after being exposed to sunlight. Not many foods are naturally rich in vitamin D, but it is found in fatty fish such as salmon, and milk commonly is fortified with it.
Vitamin D deficiency can lead to osteoporosis in adults or rickets in children.
In MS, communication between the brain and other parts of the body is disrupted. Many experts believe MS is an autoimmune disease in which the body, through its protective system, attacks its own tissues.
In some people, MS can lead to paralysis.
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