Exercise and moderate caffeine consumption together could help ward off sun-induced skin cancer, researchers said on Monday, but cautioned against ditching the sun screen in favor of a jog and a cappuccino.


Experiments on mice showed that caffeine and exercise together somehow made them better able to destroy precancerous cells whose DNA had been damaged by ultraviolet-B radiation, according to scientists at Rutgers University in New Jersey.

"We think that it will be important in terms of prevention, and possibly not only for skin cancer but possibly for other cancers as well," Rutgers cancer researcher Allan Conney, one of the scientists, said in a telephone interview.

The researchers studied groups of hairless mice that were exposed to lamps generating ultraviolet-B radiation that damaged DNA in their skin cells.

One group drank water containing the human equivalent of one or two cups of coffee a day. A second group exercised on a running wheel. A third group exercised and drank the caffeine. A fourth group neither exercised nor drank caffeine.

Both caffeine and exercise alone increased by roughly 100 percent the mice's ability to kill off precancerous cells that could lead to skin cancer compared to the mice that did neither. But the mice that did both showed a nearly 400 percent increase in this ability, the researchers found.

The researchers are eager to discover if the findings would apply to humans, but in the meantime warned people not to give up the sunscreen.

"Don't go out and exercise and drink a lot of coffee and assume you're going to be protected," Conney said.

"Keep in mind that these are studies in mice. Although I think that they may be applicable to humans, it really has to be studied carefully before we can say that," Conney added.

The study was published in the Proceedings of the National Academy of Sciences.

The researchers said some previous studies have provided evidence that exercise and caffeine consumption through coffee may be linked to reduced risk for some other cancers.


Conney said they want to figure out precisely how the combination of caffeine and exercise seems to have a protective effect against skin damage caused by the sun.

"It's great that people are doing research looking for different ways to help reduce the risk of skin cancer," dermatologist Dr. Bruce Katz, a spokesman for the Skin Cancer Foundation and the director of the Juva Skin & Laser Center in New York City, said in a telephone interview.

But the study provided "extremely preliminary data," and there is no evidence of such an effect in people, Katz added.

The foundation said skin cancer is the most common form of cancer in the United States, with more than 1 million people diagnosed with it annually.