Author response: Neonatal vitamin D status and risk of multiple sclerosis: A population-based case-control study.

Abstract

In response to our article,1 Dr. Zarghami suggests that clinical trials are necessary to compare the efficacy and cost–benefit of vitamin D supplementation vs sun exposure in pregnancy. Such trials are not feasible because of the relatively low frequency of multiple sclerosis (MS) and the long interval between any intervention in pregnancy and the observation of its potential effect on MS risk in offspring. We agree, nevertheless, that judicious sun exposure provides an alternative approach for the correction of vitamin D deficiency in regions with levels of ultraviolet B radiation high enough to support year-round vitamin D production. This is not the case in countries like Denmark, where winter sunlight cannot produce sufficient vitamin D levels.2