Date published: 2007/07/29
The BBC says:
People who spend more time in the sun as children subsequently have a lower risk of developing multiple sclerosis (MS), a US study shows. The University of Southern California team suggest UV rays offer protection by altering the cell immune responses or by boosting vitamin D levels.
An earlier study found women who took vitamin D supplements were 40% less likely to develop MS.
The latest research is published in the journal Neurology.
MS is among the most common neurological diseases affecting around two million people worldwide.
However, it is more common at higher latitudes, which generally have lower levels of ultraviolet radiation - the type produced by the sun.
People in these countries are exposed to less sunlight, which triggers a chemical reaction in the body leading to vitamin D production.
For the study, researchers surveyed 79 pairs of identical twins who had the same genetic risk of MS.
In each pair, one of the twins had MS.
The twins were asked to specify whether they or their twin spent more time outdoors during hot days, cold days, and summer, and which one spent more time basking in the sun, going to the beach and playing team sports as a child.
The researchers found the twin with MS spent less time in the sun as a child than the twin who did not have MS.
Depending on the activity, the twin who spent more hours outdoors had up to a 57% reduced risk of developing MS.
There is always a risk with health studies of confusing correlation and causation. Here they have not proven a causation, but they have gotten pretty close. But as with other health studies, they have only looked at one thing in isolation. Everybody also knows that too much sun is not very healthy for you either. So unless they can give a prescription for how much sun is needed, and how to balance that against the risk of too much sun, and unless they can say who is at risk from MS (most people are not), then the research is of limited use.
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