BMJ  2007;334:13 (6 January), doi:10.1136/bmj.334.7583.13-c

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High serum vitamin D may protect against multiple sclerosis

The effect of geographical latitude on the incidence of multiple sclerosis led decades ago to the hypothesis that sun exposure and vitamin D protect against this debilitating disease, but this has not been confirmed by studies. A case control study nested in a cohort of more than seven million US military personnel compared serum concentrations of 25-hydroxyvitamin D in 257 people who later developed multiple sclerosis and matched controls without the disease.

In white men and women, the risk of multiple sclerosis decreased by 40% with every 50 nmol/l increase of circulating vitamin D. No such association was found in black people and Hispanics, who had lower circulating concentrations than white people. The association was particularly strong for serum vitamin D in white people under 20 years.

The authors discuss recent physiological studies that shed light on the role of vitamin D in the immune response, which could support a direct role for vitamin D in preventing multiple sclerosis. Other potential explanations exist: confounding by a genetic predisposition to both multiple sclerosis and low concentrations of circulating vitamin D or effects of exposure to sunlight unrelated to vitamin D production.

We might know more if the authors' call for trials assessing the preventive potential of vitamin D supplementation in relatives of people with multiple sclerosis is answered.

References

JAMA 2006;296:2832-8[Abstract/Full Text]

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