According to new study findings, people who have spent more time in the sun and those with higher vitamin D blood levels are less likely to develop multiple sclerosis.
Previous studies have shown that people living close to the equator have a lower risk of multiple sclerosis (MS) than those at higher latitudes, a difference that may be explained by more sun exposure and higher vitamin D levels in the blood. (Sun exposure triggers vitamin D synthesis in the skin.)
To investigate, researchers at The Australian National University studied more than 200 adults who started having the first symptoms of MS between 2003 and 2006.
They found a comparison group of nearly 400 people from the same regions of Australia, who matched the subjects in age and gender, but had no signs or symptoms of MS.
Participants in both groups 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 measured.
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.
As well, people with early MS were less than half as likely to have high levels of skin damage caused by sun exposure and had blood vitamin D levels 5 to 10 percent lower than people without MS.
More research is needed to determine if greater sun exposure really does lower the risk of developing multiple sclerosis. Since sun exposure is associated with a higher risk of skin cancer, more time outside is not necessarily healthier. Nor do the results mean that everybody should load up on vitamin D, health experts warn.
The main message of the study is that small amounts of sun exposure are probably optimal both for maintaining vitamin D levels and for other health benefits.
The study was published in the journal Neurology.
Leslie's note: While there are no recommended vitamin D intakes to prevent MS, the Canadian Cancer Society advises adults to take 1000 international units (IU) of vitamin D daily in the fall and winter to help reduce the risk of certain cancers. Adults over 50, people with dark coloured skin and those who don't get outdoors in the summer months should supplement year round. Older adults, people with dark coloured skin and individuals who are obese may require a higher dose of vitamin D to reach a sufficient blood level. Up to 2000 IU per day is considered safe.
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