There is a “strong case” for giving pregnant women vitamin D supplements to ward off multiple sclerosis (MS) between the months of October and March.
A study, published in the Journal of Neurology Neurosurgery and Psychiatry, shows the risk of developing MS is highest in the month of April and lowest in October.
The analysis indicated a significant excess risk of 5% among those born in April with the risk of MS was 5 to 7% lower among those born between October and November.
Researchers claim the findings “strongly implicate” maternal exposure to vitamin D during pregnancy.
Data of 152,000 MS sufferers from around the world were analysed. It was found that in countries with latitudes greater than 52 degrees from the equator, insufficient ultraviolet light of the correct wavelength (290 to 315 nm) reaches the skin between October and March to enable the body to manufacture enough vitamin D during the winter months.
No studies from the southern hemisphere were included in the analysis - largely because it is claimed so few have been carried out, leading the researchers to urge caution in when interpreting the results.
“Through combining existing datasets for month of birth and subsequent MS risk, this study provides the most robust evidence to date that the month of birth effect is a genuine one,” said the researchers.
“This finding, which supports concepts hypothesised some years previously, surely adds weight to the argument for early intervention studies to prevent MS through vitamin D supplementation.”