As children, we all liked to play outside during the long, hot summer days - but could we have also been building a natural resistance to multiple sclerosis?

Researchers in Tasmania believe that's just what we were doing. The more we spent in the sun when we were aged between six and 15 years, the less the risk we run later in life of developing MS.

If true, it suggests that vitamin D and ultraviolet light might also be MS fighters.

But is it true? Researchers from the University of Tasmania tested the theory by questioning 136 MS sufferers, and 272 healthy controls.

Tasmania has a higher-than-average prevalence of MS in common with other regions at the extremes of latitude, and this, coupled with the theory that ultraviolet radiation may have a protective role in T-helper cell autoimmune diseases such as MS, gave the researchers the clue that sunshine exposure could have a part to play.

Unfortunately, most of the participants were aged 60 and over, and were being asked to remember how much time they spent in the sun up to 54 years earlier. Their skin phenotype and melanin density were also checked to verify their memories.

The results suggest an association, and exposure to winter sun when young has an even stronger preventative role, the researchers conclude.

(Source: British Medical Journal, 2003; 327: 316-20).