A combination of coffee drinking and regular exercise may help to lower the risk of developing skin cancer, according to scientists in the US.
The two are thought to work together to kill off precancerous cells whose DNA has been damaged by ultraviolet-B radiation from the sun.
If the cells are left to divide, they can form malignant skin cancers and ultimately become fatal.
Rates of skin cancer in the UK have quadrupled for men and tripled for women in the past 25 years.
The disease is the fastest growing cancer in the UK, partly because more people are taking sunshine holidays abroad.
More than 8,000 cases of malignant melanoma, the most dangerous form of skin cancer, are diagnosed in the UK every year, leading to almost 2,000 deaths.
At least 75,000 cases of non-melanoma skin cancer, a much milder and less harmful disease, occur each year in the UK.
Previous studies have suggested that exercise and coffee may each play a small role in protecting against skin cancer, but the latest research shows for the first time that when combined, the two may offer far more protection.
Scientists led by Allan Conney at Rutgers University, New Jersey, examined the effect of ultraviolet light on mice bred to be hairless, and so particularly vulnerable to the effects of sunlight.
Four groups of mice were exposed to UV-B radiation, but were given different diets and exercise regimes. One group drank caffeinated water, giving them a caffeine intake equivalent to one to two cups of coffee a day. A second group was fed pure water but allowed to exercise on a running wheel.
The third group was given caffeine and access to a running wheel, while the fourth did no exercise and had no caffeine.
The scientists later took samples and checked for signs of UV-induced genetic damage. They also looked for evidence of a natural survival mechanism called apoptosis, in which damaged and potentially cancerous cells are forced to commit suicide before they can form tumours.
The tests showed that caffeine alone led to a 95% increase in programmed cell death and there was a 120% increase from exercise alone. But when combined, exercise and caffeine led to a four-fold increase in cell death, suggesting the body was able to rid itself of pre-cancerous cells much more effectively.
Details of the study appear in the US journal Proceedings of the National Academy of Sciences.
The team plans to investigate the underlying reasons for its findings before organising a clinical trial in humans.
