Drinking a double espresso a day and taking regular exercise may help to prevent skin cancer, researchers say.

Low to moderate amounts of caffeine in combination with exercise can be good for health and prevent damage caused by the Sun’s ultraviolet rays, a study on mice suggests.

Skin cancer is one of the most common cancers in Britain and is becoming more widespread — the number of cases has doubled in the past 20 years.

The study, at Rutgers University in New Jersey, showed that a combination of exercise and some caffeine — equivalent to one or two cups of coffee a day — protected against the effects of the Sun’s ultraviolet-B (UVB) radiation, which can lead to cancer. The caffeine and exercise seemingly conspire to kill off precancerous cells whose DNA has been damaged by UVB-rays, the authors say.

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Each year in Britain, there are more than 65,000 new cases of non-melanoma skin cancer and more than 8,000 new cases of malignant melanoma. Non-melanoma is nearly always curable if caught early enough. But about 1,800 people die from malignant melanoma skin cancer annually — despite four out of five cases being preventable.

The study is published today in Proceedings of the National Academy of Sciences, the American journal.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 — equivalent to up to two cups of coffee for humans — another voluntarily exercised on a running wheel, while a third group both drank caffeine and ran. A fourth group, which served as a control, neither ran nor drank caffeine.

All of the mice were then exposed to lamps that generated UVB radiation that damaged the DNA in their skin cells. The Rutgers team then looked for evidence of programmed cell death, also known as apoptosis, among the four groups of UVB-treated mice. Apoptosis is the process by which cells with badly damaged DNA destroy themselves as a natural defence against illness and infection.

Drugs that induce apoptosis are currently being investigated as a means of preventing different types of cancer, but Allan Conney, one of the authors, said that the combination of caffeine and exercise appeared to have a similar protective effect.

Compared with the UVB-exposed control animals, the caffeine drinkers showed an increase of about 95 per cent in UVB-induced apoptosis, the exercisers showed a 120 per cent increase, while the mice that were both drinking and exercising showed a nearly 400 per cent increase. The cumulative difference seen in the caffeine-drinking runners, “can likely be attributed to some kind of synergy between the two factors”, Dr Conney said.

In Britain, 80 per cent of adults drink coffee every week. It is not the only beverage to contain caffeine, but it does contain the most. People with high blood pressure, and pregnant women, are advised to limit their caffeine consumption, however. Previous research has found that coffee may reduce the risk of developing gallstones, kidney stones and colorectal cancer.

Alison Ross, science information officer at the charity Cancer Research UK, said: “This study was carried out in mice so there will need to be more research to see if there is a similar effect in humans. Drinking a cup of coffee before going out jogging is definitely not a substitute for adequate sun protection — and those who are fair-skinned should take extra care.”

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