By Pat Anson, Editor

Vitamin D levels in the blood may help predict whether a person is at risk of developing multiple sclerosis, according to a large new study published online in the journal Neurology.

The findings provide the best evidence to date that low levels of Vitamin D may be a contributing factor to multiple sclerosis (MS), a chronic and incurable disease which attacks the central nervous system.

“There have only been a few small studies suggesting that levels of vitamin D in the blood can predict risk,” said study author Kassandra Munger, ScD, of the Harvard T.H. Chan School of Public Health in Boston. “Our study, involving a large number of women, suggests that correcting vitamin D deficiency in young and middle-age women may reduce their future risk of MS.”

Munger and her colleagues analyzed a database derived from blood samples taken during prenatal testing of over 800,000 Finnish women. Using hospital and prescription records, they were able to identify 1,092 of those women who were later diagnosed with MS. They were compared to a control group of 2,123 women who did not develop the disease.

Of the women who developed MS, 58% had deficient blood levels of vitamin D, compared to 52% of the women who did not develop the disease.

Deficient blood levels of vitamin D were defined as fewer than 30 nanomoles per liter (nmol/L). Insufficient levels were 30 to 49 nmol/L and adequate levels were 50 nmol/L or higher.

Researchers found that with each 50 nmol/L increase in vitamin D in the blood, the risk of developing MS later in life decreased by 39 percent. In addition, women who had deficient levels had a 43% higher risk of developing MS than women who had adequate levels.

“More research is needed on the optimal dose of vitamin D for reducing risk of MS,” said Munger. “But striving to achieve vitamin D sufficiency over the course of a person’s life will likely have multiple health benefits.

"Our results further support and extend those of previous prospective studies of (Vitamin D) levels in
young adults and risk of MS, and suggests that many individuals are exposed to an increased MS risk that
could be reduced by broad population-based programs to prevent vitamin D deficiency."

Participants in the study were primarily white women, so the findings may not be the same for other racial groups or men. Also, while the blood samples were taken an average of nine years before MS diagnosis, it is possible some women may have already had MS when their blood was drawn and were not yet showing symptoms of the disease.

MS causes numbness in the limbs, difficulty walking, paralysis, loss of vision, fatigue and pain. Symptoms begin with a series of irregular relapses, and after about 20 years MS worsens into a secondary progressive stage of the disease.

Low blood levels of vitamin D – known as the “sunshine vitamin”-- have previously been linked to an increased risk of developing MS. Danish researchers found that MS patients who spent time in the sun every day during the summer as teenagers developed the disease later in life than those who spent their summers indoors.

Ultraviolet rays in sunlight are a principal source of Vitamin D, which has a wide range of positive health effects, such as strengthening bones and inhibiting the growth of some cancers.