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Coffee drinkers are less likely to suffer from malignant melanoma, and their risk decreases somewhat with every cup they swallow, according to findings published Jan. 20 in the Journal of the National Cancer Institute.
"We found that four or more cups of coffee per day was associated with about a 20 percent reduced risk of malignant melanoma," said lead author Erikka Loftfield, a doctoral student at Yale University School of Public Health who is completing her dissertation work at the U.S. National Cancer Institute.
Previous research has shown that coffee drinking could protect against less deadly forms of skin cancer, apparently by mitigating the damage to skin cells caused by the sun's ultraviolet rays, the researchers said in background notes.
They decided to see if this protection extended to melanoma, the leading cause of skin cancer death in the United States and the fifth most common cancer. In 2013, there were an estimated 77,000 new cases of melanoma and about 9,500 deaths from the cancer, according to the study.
The researchers gathered data from a study run by the U.S. National Institutes of Health and AARP. A food questionnaire was sent to 3.5 million AARP members living in six states: California, Florida, Louisiana, New Jersey, North Carolina and Pennsylvania; as well as two cities, Atlanta and Detroit.
The questionnaire yielded coffee drinking info for nearly 447,400 white seniors in 1995 and 1996, and researchers followed up with the participants for about 10 years on average.
All participants were cancer-free when they filled out the questionnaire, and the researchers adjusted for other factors that could influence melanoma risk. These included ultraviolet radiation exposure, body mass index, age, sex, physical activity, alcohol intake and smoking history.
They found that people who drank the most coffee every day enjoyed a lower risk of melanoma, compared with those who drank little to no coffee.
There was also a trend toward more protection with higher intake. People who drank one to three cups a day had about a 10 percent decreased risk of melanoma compared with those who drank none at all, while those who drank four or more cups had a 20 percent decreased risk.
The study only uncovered an association between coffee consumption and melanoma risk; it didn't prove a cause-and-effect relationship.
Caffeine could be the reason for the apparent protection. The researchers found a significant decrease in melanoma risk only among those who drank caffeinated coffee, and previous studies have indicated that caffeine could protect skin cells against ultraviolet-B radiation, Loftfield said.
However, most of the people in the study drank caffeinated coffee, which made it difficult to fully analyze the health benefits of decaf. There could be other compounds in coffee besides caffeine that also protect against skin cancer, including antioxidants. "We certainly cannot rule that out as a possibility," Loftfield said.
This isn't the first study to look into the effect that coffee drinking might have on cancer risk, said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society.
"Coffee has been around the block several times in a variety of cancers, in terms of whether it increases or decreases risk," he said, noting that the findings have been very mixed.
Lichtenfeld said the researchers behind the new study made a good basic science case for the possibility that coffee might protect against skin cancer. However, because this study was not a clinical trial, it didn't prove cause and effect.
"As a result of that, one cannot conclude that in 'real life' coffee actually decreases the risk of melanoma," he said.
Even with these findings, Loftfield said people should not rely on coffee to protect them from melanoma. Sunscreen, long sleeves and a wide-brimmed hat will do more than a mug of java ever could.
"The main message really is that sun and [ultraviolet] radiation exposure are the major risk factors for melanoma," she said. "It is important to study other factors to better understand the cause of this disease, but we must keep these major risk factors in mind."
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