WASHINGTON -- Can adding a cup or two of coffee to the exercise routine increase protection from skin cancer? New research indicates that just might be the case.
The combination of exercise and caffeine increased destruction of precancerous cells that had been damaged by the sun's ultraviolet-B radiation, according to a team of researchers at Rutgers University.
Americans suffer a million new cases of skin cancer every year, according to the National Cancer Institute.
In mice there is a protective effect from both caffeine and voluntary exercise, and when both are provided, not necessarily at the same time, protection is further enhanced, said Dr. Allan H. Conney of the laboratory for cancer research at Rutgers.
"We think it likely that this will extrapolate to humans, but that has to be tested," Conney said in a telephone interview.
Nonetheless, people should continue to use sunscreen, he said.
Exposing the mice to ultraviolet-B light causes some skin cells to become precancerous.
Cells with damaged DNA are programmed to self-destruct, a process called apoptosis, but not all do that, and damaged cells can become cancerous.
In today's issue of Proceedings of the National Academy of Sciences researchers report stunning results from caffeine-fed mice that exercised. The researchers studied hairless mice in four groups: Some were fed water containing caffeine; some had wheels on which they could run; some had both; and a control group had neither.
"The most dramatic and obvious difference between the groups came from the caffeine-drinking runners, a difference that can likely be attributed to some kind of synergy," Conney said.
Compared with the control animals, those drinking caffeine had a 95 percent increase in apoptosis in damaged cells. The exercisers showed a 120 percent increase, and the mice that were both drinking and running showed a nearly 400 percent increase.
Just what is causing that to happen is not yet clear, though the researchers have several theories.
"We need to dig deeper into how the combination of caffeine and exercise is exerting its influence at the cellular and molecular levels, identifying the underlying mechanisms," Conney said.
"With an understanding of these mechanisms we can then take this to the next level, going beyond mice in the lab to human trials," he said. "With the stronger levels of UVB radiation evident today and an upward trend in the incidence of skin cancer among Americans, there is a premium on finding novel ways to protect our bodies from sun damage."
Conney said the researchers were originally interested in the effects of green tea in preventing skin cancer and were doing tests on regular and decaffeinated teas
They found the regular tea had an effect, but not the decaffeinated brew. Meanwhile, the researchers observed that caffeinated mice were more active than those that weren't, so they decided to study the effects of exercise, too.
They put running wheels into some of the cages, and the mice would run often.
Although both caffeine and exercise helped eliminate damaged skin cells, combining them worked better than either alone.
Dr. Michael H. Gold, a Nashville dermatologist and a spokesman for the Skin Cancer Foundation, said "the concept of systemic caffeine should be addressed further."
"I think the concept potentially has a lot of merit," he said in a telephone interview. But mice and humans are different and studies need to be done to be sure this also applies to people.