Caffeine and Exercise Can Team Up to Prevent Skin Cancer

Regular exercise and little or no caffeine has become a popular lifestyle choice for many Americans. But a new Rutgers study has found that it may not be the best formula for preventing sun-induced skin damage that could lead to cancer. Low to moderate amounts of caffeine, in fact, along with exercise can be good for your health.

Groups of hairless mice, whose exposed skin is vulnerable to the sun, were the test subjects in experiments in which one set drank caffeinated water (the human equivalent of one or two cups of coffee a day); another voluntarily exercised on a running wheel; while a third group both drank and ran. A fourth group, which served as a control, didn’t run and didn’t caffeinate. All of the mice were exposed to lamps that generated UVB radiation that damaged the DNA in their skin cells.

Some degree of programmed cell death, also known as apoptosis, was observed in the DNA-damaged cells of all four groups, but the caffeine drinkers and exercisers showed an increase over the UVB-treated control group. Apoptosis is a way in which cells with badly damaged DNA commit suicide – UVB-damaged cells in this case.

“If apoptosis takes place in a sun-damaged cell, its progress toward cancer will be aborted,” said Allan Conney, director of Rutgers’ Cullman Laboratory.

Compared to the UVB-exposed control animals, the caffeine drinkers showed an approximately 95 percent increase in UVB-induced apoptosis, the exercisers showed a 120 percent increase, while the mice that were both drinking and exercising showed a nearly 400 percent increase.

“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. The authors suggested several mechanisms at the biochemical level that might be responsible for the protective effects of caffeine and exercise, but acknowledged that what is happening synergistically is still somewhat of a mystery.

In both groups, the number of tumors per mouse increased with time, but animals with access to running wheels had approximately 32 percent fewer tumors than animals without running wheels. Tumor size per mouse in the non-exercising group was on average more than three times greater than for the group with the running wheels.

As might be expected, the exercising mice ate and drank more but had less body fat than their more sedentary associates, and the number of tumors also decreased with lower body fat.

In another first, the researchers also detected what could be the mechanism responsible for this effect. Subsequent to the studies reported in the journal article, they conducted follow-up work that suggests that exercise enhances UVB-induced apoptosis (programmed cell death) both in the skin – a normal, protective process that removes sun-damaged cells – and in UVB-induced tumors.

While all these conclusions are based on laboratory studies on mice, and it is not yet known whether exercise decreases the risk of sunlight-induced skin cancer in humans. Clinical trials are needed to investigate this further. In bowel cancer, however, evidence from population studies already suggests that physically active people have a reduced risk of developing the disease, but the mechanisms remain unclear.