WASHINGTON, July 30 (Xinhua) -- Regular exercise and little or no caffeine has become a popular lifestyle choice for many Americans. But a new 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.

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    A research team at The State University of New Jersey, showed that a combination of exercise and some caffeine protected against the destructive effects of the sun's ultraviolet-B (UVB) radiation, known to induce skin cancer. The caffeine and exercise seemingly conspire in killing off precancerous cells whose DNA has been damaged by UVB-rays.

    The studies appear in the July 31 Proceedings of the National Academy of Sciences.

    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, one of the paper's authors.

    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 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.

    "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.