Outrunning Melanoma

Exercise may prevent skin cancer.

By Victor LimjocoMay 25, 2006 5:00 AM


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As we head to the beach this summer, we know we should bring along some sunscreen.

But now researchers say that a good dose of exercise might also help protect you from skin cancer.

Rutgers University cancer researcher Allan Conney found that hairless mice that work out get fewer skin tumors when exposed to ultraviolet rays.

As he reported in the journal "Carcinogenesis," mice with running wheels in their cages had 32 percent fewer UV-induced tumors than mice without running wheels. "You shine UV light on them, they had fewer skin tumors than the animals without runwheels," Conney says. "Voluntary exercise inhibited UV light-induced skin cancer."

Exercise even prevented tumors in mice that had already been exposed for long periods to UV light. "This could be similar to people that are heavily exposed when they're children out on the beach a lot and later in life they're not exposed to as much sunlight," Conney says. "The mice love to go on the runwheel, sometimes two or three of them at a time," Conney says. Some mice ran up to three miles a day. While these exercising mice ate more, they weighed the same at the end of the study and had less body fat than the sedentary mice.

Conney thinks that decrease in body fat may be important in this protective mechanism. "Those mice, even in the exercising group, that had lower amounts of fat had fewer tumors," he says.

He also found that the exercising mice seemed better able to destroy skin cells damaged by the sun. When cells are injured, they die to prevent further damage. "The sunlight causes DNA damage in the cell, and the body has a way to eliminate those cells from the body by a process called apoptosis, " Conney explains. That beneficial process of "cell suicide" was sped up in the skin of exercising mice.

While sunscreen is still key to preventing skin cancer, Conney thinks if a controlled study were done in people, his findings in exercising mice would hold true for us. But he notes that forced exercise might not have the benefits of voluntary exercise. "So it raises a question," he says. "If one's wife tells you to go exercise, is that forced exercise or voluntary exercise?"

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