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Study Finds Lower Risk of Breast Cancer With Higher Sunlight Exposure

We've all been warned over and over to avoid sunlight in order to avoid skin cancer, but... conflicting with that advice are studies linking higher sunlight exposure to lower levels of other cancers, health benefits (e.g. lower blood pressure), and early death (mortality). One such recent study found that higher sun exposure over the years is associated with a lower risk of breast cancer in women.

The Univ. of Buffalo and Univ. of Puerto Rico researchers conducted the study in Puerto Rico, where people live with high year round sun exposure. 635 women participated in the study.

From Medical Xpress: Study in Puerto Rico finds lower risk of breast cancer with more sun exposure

The sun is almost always shining during the day in San Juan, Puerto Rico, and that makes the findings of a new study on breast cancer and sun exposure particularly noteworthy. 

In a new study by researchers from the University at Buffalo and the University of Puerto Rico, there was a lower risk of breast cancer associated with greater sun exposure. 

Researchers used a chromameter to compare skin pigmentation in unexposed and exposed skin in 307 cases and 328 controls. The difference in skin pigmentation provided an estimate of usual sun exposure.

"This study was unique in that it was of Puerto Rican women, which allowed for us to look at this association in a population with a wide range of skin color and with year-round high sun exposure," said study senior author Jo L. Freudenheim, a SUNY Distinguished Professor in the Department of Epidemiology and Environmental Health in UB's School of Public Health and Health Professions.

There is some, albeit inconsistent, evidence that sun exposure is associated with lower risk of breast cancer. There are a number of reasons that may explain this finding, says Freudenheim.

"One step in the internal production of vitamin D occurs when skin is exposed to sun," she said. "Sun exposure also affects the body in a number of other helpful ways, with effects on inflammation, obesity and circadian rhythms. While recent recommendations have been to limit sun exposure to prevent skin cancer, there may also be a benefit to some sun exposure, especially exposure without sunburn."

The previous studies on sun exposure and breast cancer have been conducted in places that experience seasonal variation in ultraviolet radiation, including periods of low to no exposure. In Puerto Rico, however, there is no significant seasonal fluctuation, with the potential for continuous exposure to high UV radiation for those who spend time outdoors.

"The study provided consistent results across different parameters," said paper first author Cruz Nazario, Ph.D., an epidemiology professor at the University of Puerto Rico. "Breast cancer risk was lower for women with the highest accumulated sun exposure. Similarly, the risk was lower independent of estrogen receptor status, and it was even lower among participants with darker skin color."

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