Researchers at New Jersey-based Rutgers University have found that drinking coffee and exercising speeds up the killing off of cells damaged by ultraviolet-B radiation.

The study specifically examined UVB apoptosis -- the programmed death of cells that become damaged by ultraviolet rays -- in hairless mice. This sort of cell-suicide helps prevent the formation of deadly melanoma skin cancer

For the study, the mice were divided into four groups. The first group drank the human equivalent of one or two cups of coffee per day. The second group had regular exercise on a running wheel. The third had both caffeine and exercise, and a fourth group had none of either.

Researchers said they were surprised to find that the rate of cell suicide was 400 percent greater in mice that both drank caffeine and exercised, when compared to the control group. When combined, caffeine and exercise also "markedly" decreased tissue fat in the mice, the researchers said.

Separately, caffeine and exercise also appeared to help speed-up this type of cell death. Mice that only drank coffee, for example, had 95 percent increase in UVB-induced apoptosis, and those that only exercised showed a 120 percent increase.

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 even more than the sum of the two, said Dr. Allan H. Conney of the laboratory for cancer research at Rutgers.