NEW YORK (Reuters Health) - Exposure to sunlight may reduce the risk of advanced breast cancer in women with light skin pigmentation, according to the results of a population-based study appearing in the American Journal of Epidemiology.
"We believe that sunlight helps reduce women's risk of breast cancer because the body manufactures the active form of vitamin D from exposure to sunlight," lead author Dr. Esther M. John, from the Northern California Cancer Center in Fremont, 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."
The study is not the first to link sun exposure with a reduced risk of breast cancer, but the way that sun exposure was measured was new, according to John.
"We 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. Other studies have usually relied on self-reported sun exposure," she told Reuters Health.
The study included 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). In addition to the sun exposure test mentioned, skin specimens were obtained and analyzed in a subgroup of subjects in each group.
High levels of sun exposure were associated with a 47-percent reduced risk of advanced breast cancer in light-skinned women, the results show. 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 and was only apparent for advanced disease, not localized breast cancer.
The results could have important public health implications, but they will require confirmation in other studies, the authors conclude.
"While the public needs 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," John said.
The evidence is increasing that vitamin D may decrease the risk of certain cancers, such as breast, prostate and colon cancers. A safe way to get vitamin D is from supplements."
SOURCE: American Journal of Epidemiology October 18, 2007.
The study reviewed here showed that high levels of sun exposure lowered the risk of advanced breast cancer in light-skinned women by 47% compared to light-skinned women who got less sun exposure. Exposure to high levels of sunlight didn't have the same benefit for women with darker skin.
When your body is exposed to sunlight, it produces vitamin D. Light-skinned people produce more vitamin D when they get sun compared to people with darker skin. Vitamin D appears to be the link between sunlight and reduced risk.
Along with calcium, vitamin D is especially important for bone health. Many research studies also have shown a link between healthy levels of vitamin D and calcium and reduced breast cancer risk. A healthy diet is one of the best ways to give your body the vitamin D and calcium it needs. But if you think you're not getting enough of these important nutrients, you can also take a supplement. Talk to your doctor about a supplement that's right for you. A little bit of regular sun exposure also can help you get enough vitamin D.
At the same time, it's important to remember that excessive sun exposure increases the risk of skin cancer. Only a little sunlight is necessary to help your body use both calcium and vitamin D. Getting 10 minutes of sun on your face and hands each day gives you the benefits of sunlight without the risks. If you're going to be outside longer, make sure you use sunscreen and reapply it regularly.
Stay tuned to breastcancer.org for the latest news on steps you can take to make sure your risk is a low as it can be.
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