Sun Exposure and Vitamin D

An Australian study published in the issue of 'Neurology' (8 February) provides additional evidence for a potential role for low levels of sunlight exposure and vitamin D as triggers for multiple sclerosis.

Vitamin D is manufactured by the skin when it is exposed to sunlight. Studies of the geographical distribution of MS support the link between lack of sunlight exposure, consequent lack of vitamin D production, and the development of MS.

In this study, two groups of people were compared - those with first signs of MS (216 in total) and a second group (395 people) matched for age and gender but with no signs of MS. Both groups of people were asked how much time they had spent in the sun and where they had lived at different points in their lives; skin damage from the sun and the level of vitamin D in their blood were also checked.

On average, people with the first signs of MS had been exposed to a smaller "UV dose" based on how much time they had spent in the sun and how close to the equator they had lived over the course of their lives.

People with most evidence of skin damage were 60% less likely to show first signs of MS. People with the highest levels of vitamin D were also less likely to have experienced initial symptoms of MS.

According to the researchers the main message of the study is that "small amounts of sun exposure ... occurring frequently, are probably optimal both for maintaining vitamin D levels and for other health effects."

Sun exposure and vitamin D are independent risk factors for CNS demyelination: Lucas RM, Ponsonby AL., Dear K et al. Neurology 2011; 76:540-548

Multiple Sclerosis Trust Website