Does Vitamin D Influence Multiple Sclerosis Risk?

The notion that vitamin D is involved in multiple sclerosis (MS) etiology was originally proposed to explain the geographical distribution of MS. MS prevalence increases with increasing latitude and decreasing ultraviolet radiation exposure.

In addition, there is an apparent “month of birth” effect in MS-in the Northern Hemisphere, more patients with MS are born in April or May compared with November. This effect was thought to be vitamin D related because a mother who is pregnant over the summer and delivering in November would have more sunshine exposure and consequently more vitamin D than a mother who is pregnant over the winter and delivering in April.

This factor raised the hypothesis that vitamin D levels at birth may determine MS risk. This study aimed to directly test that hypothesis.

The study, a population-based case-control investigation in Sweden, used stored blood spots (Guthrie cards taken at birth) from 459 cases of MS and 663 controls randomly drawn from a national population registry and matched on sex, age, and residential area. Vitamin D levels were measured in the blood spots.

The study showed no association between neonatal 25-hydroxyvitamin D levels and risk of MS (crude odds ratio = 1.0, 95% confidence interval = 0.68-1.44, for the highest 25-hydroxyvitamin D quintile compared with the lowest).

This study used the wealth of Swedish health care data to address an important question. The authors’ conclusion questions the role of vitamin D in influencing risk. Vitamin D levels during pregnancy certainly do not appear to influence MS risk to any substantial extent.

The question now is whether vitamin D truly influences MS risk. If it does, the effect of vitamin D must occur at a later stage than during pregnancy.

References:

1. Ueda P, Rafatnia F, Bäärnhielm M, et al. Neonatal vitamin D status and risk of multiple sclerosis. Ann Neurol. 2014 Jul 1. doi: 10.1002/ana.24210. [Epub ahead of print]