(Oct 24) Exposure to sunlight - which boosts levels of vitamin D in the body - may reduce the risk of advanced breast cancer, according to a US study published online this week in the American Journal of Epidemiology.

The study of 1,788 breast cancer patients and 2,129 women who didn't have the disease found that women with high sun exposure had half the risk of developing advanced breast cancer than women with low sun exposure. However, this effect was noted only in women with naturally light skin colour.

'We believe that sunlight helps to reduce women's risk of breast cancer because the body manufactures the active form of vitamin D from exposure to sunlight,' lead researcher Esther John, of the Northern California Cancer Centre, said in a statement.

'It is possible that these effects were observed only among light- skinned women because sun exposure produces less vitamin D among women with naturally darker pigmentation.'

Ms John and her colleagues emphasised that women should not sunbathe in an attempt to reduce their breast cancer risk.

'If future studies continue to show reductions in breast cancer risk associated with sun exposure, increasing vitamin D intake from diet and supplements may be the safest solution to achieve adequate levels of vitamin D," co-researcher Gary Schwartz, of the Comprehensive Cancer Centre at Wake Forest University School of Medicine, said in a statement.