Pregnant women in northern countries need to get sunlight to protect themselves – but this may not help their babies, researchers reported last night.
A Swedish study conducted over nearly 40 years sought to examine the impact of vitamin D – linked to sunshine exposure – during pregnancy in preventing multiple sclerosis.
The vitamin is generated in the body by exposure to sunlight and recent studies have linked shortages to high rates of multiple sclerosis to northern countries with limited winter sunshine.
Researchers concluded that pregnant women with high levels of vitamin D failed to pass on protection to their children.
The researchers, from Umeå University Hospital, were able to study nearly 300,000 blood samples collected from 164,000 people in northern Sweden since 1975 and identify vitamin D levels.
Some 192 people developed multiple sclerosis while 37 samples came from women whose children went on to develop the disease.
The analysis, reported in the journal Neurology, showed that women with high levels of the vitamin had a 61% reduced risk of developing the disease.
In general few people had high levels of the vitamin – about 8% – and just 4% of those who developed the disease had high levels.
Researcher Dr Jonatan Salzer said: "Since we found no protective effect on the baby for women with higher levels of vitamin D in early pregnancy, our study suggests the protective effect may start in later pregnancy and beyond.
“Another interesting finding in our study was that the vitamin D levels became gradually lower with time from 1975 and onward. It is possible that this decline in vitamin D status is linked to the increasing numbers of MS cases seen worldwide."
Neurology November 20 2012
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