February 4, 2005

Study puts new twist on sunlight’s cancer role

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photo by Neil Brake

Study puts new twist on sunlight’s cancer role

Two new independent studies suggest that sun exposure may actually protect against certain types of cancer.

In the Feb. 2 edition of Journal of the National Cancer Institute, researchers report that heavy sun exposure has beneficial effects on the incidence and outcome of some cancers. The findings challenge the well-established link between excessive sun exposure and cancer.

Accompanying those studies, an editorial by Vanderbilt University Medical Center faculty Kathleen Egan, Sc.D., Jeffrey Sosman, M.D., and William Blot, Ph.D., puts these findings into perspective and discusses their implications for public health.

In the first study, researchers at the Karolinska Institute in Stockholm, Sweden, examined the relationship between sun exposure and the incidence of lymphoma.

Although they had predicted that high amounts of sun exposure would be associated with an increased risk of this type of cancer, the researchers found just the opposite — that increased amounts of sun exposure actually decreased the risk of non-Hodgkin lymphoma. This relationship also held up, to a lesser extent, in Hodgkin lymphoma.

In the second study, researchers at the University of New Mexico investigated the impact of sun exposure on patients diagnosed with melanoma, the skin cancer most often associated with sun exposure. They found that melanoma patients who reported high levels of sun exposure were less likely to die.

The idea that sunlight has beneficial effects on some types of cancer is not entirely new or unexpected. In the editorial, Blot and colleagues detail how vitamin D, the vitamin produced by the skin in response to sunlight, may mediate these beneficial effects of sun exposure.

This new evidence does not necessarily mean that people should start skipping the sunscreen or begin baking under sunlamps.

“The risks and benefits of sun exposure have to be weighed against many factors, including medical history, personal attributes such as pigmentation and the proneness to sunburn, and family and personal history of cancer,” wrote Blot and colleagues.

“In view of the major potential health consequence of these results, further studies of sunlight and the vitamin D connection to cancer are certainly warranted.”