A cup of coffee could help protect your skin from the sun, US scientists say.
The easy way to avoid cancer?
A combination of exercise and caffeinated water reduced the skin-damaging effects of ultra-violet radiation in experiments on mice.
The Proceedings of the National Academy of Sciences study found the mice's natural defence against pre-cancerous cells was boosted by up to 400%.
But a UK expert warned that coffee was "definitely not a substitute" for sun protection.
The relationship between caffeine and cancer cells is under close scrutiny following evidence that it can increase a process called "apoptosis", in which the body gets rid of damaged or even cancerous cells by killing them off.
The latest research supports this, but found that adding exercise to the mixture produced a far greater benefit than expected.
The test subjects were hairless mice, who were exposed to lamps generating UVB radiation similar to the type found in sunlight.
Some of the mice were given caffeinated water to drink, some were put on an exercise wheel, and others had both.
They were then tested for the presence of body chemicals known to be linked to the levels of apoptosis taking place, and their results compared with mice who were under the sun-lamps, but getting no caffeine or exercise.
Mice who drank caffeine but did not exercise had a 95% increase in apoptosis, while those taking exercise alone had a 120% increase.
However, the mice who exercised and drank caffeine showed a massive 400% increase.
Dr Allan Conney, of Rutgers University, who led the experiment, said that the reason for this remained a mystery.
"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."
Dr Alison Ross, from Cancer Research UK, said: "This study was carried out in mice so there will need to be more research in this area 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."
Dr Stephen Alexander, from the University of Nottingham, who researches the effects of caffeine on the body, said it was plausible that caffeine might work in combination with the lifestyle of a person to produce greater effects.
He said: "Caffeine is actually added to some sports drinks these days. I could conceive quite readily that the changes that happen when you exercise have an impact on what caffeine does."
However, he cautioned against using heavily caffeinated drinks as part of a new exercise regime.
"Caffeine does have an effect on the heart-rate, and anyone considering exercising and drinking caffeine should perhaps consult their doctor beforehand to make sure they do not have any pre-existing heart problems."