Despite New Data, Increasing Sun Exposure Is Not the Way to Decrease Breast Cancer Risk

Cancer researchers and physicians have warned of the link between unprotected sun exposure and the development of skin cancer for decades, but experts from Yale Cancer Center warn that recent publicity about a new study linking a decreased risk of breast cancer to increased levels of vitamin D may be confusing.

A recent study, published in the Breast Journal, evaluated the incidence of breast cancer in 107 countries. The authors found that higher levels of serum Vitamin D and living closer to the equator correlated with a lower incidence of breast cancer.

“While ultraviolet B radiation from the sun is the primary source of vitamin D in our body, unprotected sun exposure is not a recommended way to reduce a person’s risk of developing breast cancer,” said David J. Leffell, M.D., Yale Cancer Center member and Professor and Section Chief of Dermatologic Surgery at Yale School of Medicine.

UV radiation is an undisputed carcinogen responsible for most of the estimated 1.5 million skin cancers that occur annually in the United States, he notes. “We are alarmed by the potential consequences of this study and urge women to continue to follow a careful sun protection program including the use of UV-blocking sunscreens. Women should absolutely avoid tanning salons,” Leffell said.

While this particular study showed that countries closer to the equator have lower incidence of breast cancer, many factors in addition to sunlight exposure vary across these countries, according to the Yale experts.

“The link between vitamin D and breast cancer is not clearly known at this time. One recent U.S. study actually measured blood vitamin D levels in individual women and found that women with higher blood vitamin D levels did not have significantly lower risk of subsequent breast cancer,” explained Susan Mayne, Director of Population Sciences at Yale Cancer Center and Professor of Epidemiology at Yale Schools of Medicine and Public Health. “Because the data are not consistent at this time, women who wish to reduce their risk of breast cancer should focus on more established risk factors.”

Accepted ways to decrease a woman’s risk of breast cancer include avoidance of weight gain, moderation in alcohol consumption if any, regular physical activity, and a healthy and balanced diet, say the Yale experts.

Yale Cancer Center is one of a select network of comprehensive cancer centers in the country designated by the National Cancer Institute and the only one in Southern New England. Bringing together the resources of Yale-New Haven Hospital and the Yale University School of Medicine, its mission encompasses patient care, research, cancer prevention and control, community outreach, and education. For more information visit

Citation: Breast Journal (Mar 17, 2008).

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