Low Vitamin D in Utero May Heighten Multiple Sclerosis Risk

February 12, 2010

February 12, 2010 — Vitamin D exposure before birth may play an important role in the development of multiple sclerosis later in life, a new study suggests.

New results from the Nurses' Mothers' Study, a subcohort of the well-known Nurses' Health Study, show that the risk for multiple sclerosis is lower among women whose mothers had a high intake of either vitamin D or milk during pregnancy.

"This is the first study of its kind to look at the association of gestational vitamin D and multiple sclerosis in humans," lead investigator Fariba Mirzaei, MD, from Harvard School of Public Health in Boston, Massachusetts, said during an interview.

The new study will be presented in April at the American Academy of Neurology 62nd Annual Meeting in Toronto, Ontario. It was released February 9, and the abstract will post to http://www.aan.com on February 17.

"This is exciting in that it adds to the accumulating literature on the association of vitamin D and multiple sclerosis," Lily Jung, MD, from the Swedish Neuroscience Institute in Seattle, Washington, told Medscape Neurology.

In this study, the investigators included more than 35,000 nurses whose biological mothers completed a questionnaire about their experiences and diet during their pregnancies with their now-grown daughters.

"We studied the association between maternal milk intake, maternal dietary vitamin D intake, and predicted maternal serum 25-hydroxyvitamin D during pregnancy and their daughters' risk of developing multiple sclerosis," Dr. Mirzaei explained.

About 200 women were diagnosed with multiple sclerosis. Investigators found that women born to mothers with a high milk or vitamin D intake during pregnancy were less likely to have multiple sclerosis.

Maternal Milk and Dietary Vitamin D

The age-adjusted relative risk for multiple sclerosis among the nurses with mothers consuming 4 glasses of milk per day or more compared with those consuming less than 3 glasses of milk per month was 0.44 (95% confidence interval, 0.16 - 1.23; P = .001).

The researchers report that the predicted vitamin D level in the pregnant mothers was inversely associated with the risk for multiple sclerosis in their daughters. The age-adjusted relative risk was 0.58 (95% confidence interval, 0.37 - 0.90; P = .001).

This is not the first time investigators have suggested that environmental factors are involved in multiple sclerosis susceptibility.

Reporting in an August 2009 issue of Neurology, Robert Zivadinov, MD, from the University of New York School of Medicine and Biomedical Sciences in Buffalo, showed that smoking is among the most dangerous factors linked to the development of disease (2009;73:504-510). The research team also suggested that vitamin D deficiency and Epstein-Barr infections are problematic.

"Our results suggest that some cases of multiple sclerosis could be prevented by increasing exposure to vitamin D during intrauterine life," Dr. Mirzaei said. This could be a cost-effective approach for prevention, she suggested.

More Work To Be Done

Dr. Mirzaei did, however, point to limitations to the study. "Vitamin D is mostly derived from sunlight exposure, which was not measured in this study," she noted.

"This is a retrospective questionnaire, so it depends on the memories of the mothers decades after the fact," Dr. Jung added. "Another concern is that the availability of milk can be economically determined so that it may miss an environmental exposure for the development of multiple sclerosis."

These limitations are real, Dr. Mirzaei said. "It is important to realize that our results suggest, but certainly do not prove, an association. We agree with this critique, which can only be addressed by conducting an independent investigation, possibly using biomarkers of vitamin D status in pregnancy rather than self-reported diet. We are working on this."

Still, Dr. Mirzaei says the findings will be of interest to women with multiple sclerosis and their physicians because of the higher-than-average risk for disease in their children.

The researchers have disclosed no relevant financial relationships.

American Academy of Neurology 62nd Annual Meeting. April 10-17, 2010.

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