Let the sun shine in!

posted by on October 17th, 2017

Study Links Low Vitamin D Levels in Women to MS Risk

Mark Lange, PhD

A large-scale Finish study[i] concludes that women with low levels of vitamin D in their blood are more likely to develop multiple sclerosis (MS).  MS is an autoimmune disease where the body’s own immune system attacks nerves in the brain and spinal cord. Blood samples taken from more than 800,000 pregnant women were analyzed for vitamin D and it was found that 58% of the women who developed MS had vitamin D deficiency, which was defined as lower than 30 nmol/L.  Those who were deficient in vitamin D were 43% more likely to get MS.

The results may not apply to all populations because the study group only included white women.  Furthermore, the vitamin D levels may be a surrogate measurement for sun exposure.  A previous large-scale study[ii] looked at sun exposure and MS risk for people living in Norway versus Italy.  Italy sits closer to the equator and gets more sunlight compared to Norway. Despite this, both countries have roughly the same rate of MS development.

Researchers looked at 953 cases of people with MS and 1717 controls in Norway and 707 cases of people with MS and 1333 controls in Italy.  They questioned participants about how much time they spent outdoors and their use of sunscreen.

The researchers found that infrequent outdoor activity led to an increased risk of MS in both countries.  They also found that frequent use of sunscreen during childhood in Norway led to an increased risk of MS.  They found no relationship to sunscreen use in Italy.

The results of the two studies do not necessarily contradict one other.  Research shows that sun exposure may improve immune response in multiple ways, including increasing vitamin D levels.


[i] Published online before print September 13, 2017, doi: http:/​/​dx.​doi.​org/​10.​1212/​WNL.​0000000000004489Neurology 10.1212/WNL.0000000000004489

[ii] Bjornevik, K. et al.  Sun exposure and multiple sclerosis risk in Norway and Italy: The EnvlMS study.  Multiple sclerosis, 2014.