Sunlight may reduce breast cancer risk

Exposure to sunlight may reduce the risk of advanced breast cancer in women with light skin pigmentation. Previous studies have linked sun exposure with a reduced risk of breast cancer. The association was attributed to the fact that the body manufactures an active form of vitamin D from exposure to sunlight. There has been increasing evidence that vitamin D may decrease the risk of certain cancers, such as breast, prostate and colon cancers. Researchers from the Northern California Cancer Center in Fremont studied 1788 women with breast cancer and a comparison group of 2129 "controls" - women without breast cancer, living the San Francisco Bay Area of California (1995–2003). The researchers measured women's skin pigmentation on the forehead (usually exposed to the sun) and on the upper inner arm (usually not exposed to the sun) and used the difference between the two measurements as a measure of past sun exposure. In addition to the sun exposure test, skin specimens were obtained and analysed in a subgroup of women in each group. High levels of sun exposure were associated with a 47 per cent reduced risk of advanced breast cancer in light-skinned women. Mutations of the vitamin D receptor gene did not affect the association. However, this association was not seen in women with medium or dark skin because sun exposure produces less vitamin D among women with naturally darker pigmentation. Also, the association was apparent only for advanced form of the disease, not localised breast cancer. The findings indicate that while people need to be advised to avoid excessive sun exposure, and sun burns in particular, because of the known risk of skin cancer and melanoma, never getting any sun exposure leads to vitamin D deficiency. A safe way to get vitamin D is from supplements.