Can adding a cup or two of coffee to the exercise routine increase protection from skin cancer? New research indicates that it might.
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 exercise, and when both are provided - not necessarily at the same time - protection is more than the sum of the two, 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. Nonetheless, he added, people should continue to use sunscreen.
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.
The researchers report in today's issue of Proceedings of the National Academy of Sciences that they studied hairless mice in four groups. Some were fed water containing caffeine, some had wheels on which they could run, some had both and some 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.
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.
And, he said, researchers also observed that mice drinking caffeine were more active, so they decided to study the effects of exercise, too. "What we would like to see next is a clinical trial in people," Conney said.