A new study of mice reported at a meeting in Chicago this week, suggests caffeine and exercise may cut the risk of developing skin cancers caused by exposure to the sun.

Dr Yao-Ping Lu is associate research professor of chemical biology and director of skin cancer prevention at the Rutgers Ernest Mario School of Pharmacy in Piscataway, New Jersey, and presented the findings to delegates at the American Association for Cancer Research (AACR) Annual Meeting 2012 in Chicago on Tuesday.

He said in a statement:

"I believe we may extrapolate these findings to humans and anticipate that we would benefit from these combination treatments as well".

Lu and colleagues also found evidence to suggest that fat and tumor growth are linked, and that exercise combined with caffeine may prevent not only skin cancer but also inflammation linked to other cancers that are related to obesity.

For the study, they looked at how caffeine and exercise affected mice bred to be at high risk of developing skin cancer.

Previous studies have suggested that mice given either caffeine or allowed to exercise on an exercise wheel had fewer skin cancers.

The researchers exposed the mice to UVB radiation, the component of sunlight that causes skin cancer, then put them in four groups.

One group of mice had plain water and no exercise wheel (the controls), another group had water mixed with caffeine and no exercise wheel, a third group had plain water and an exercise wheel, while the fourth group had water mixed with caffeine and an exercise wheel.

After 14 weeks of treatment, the researchers found 62% fewer non-melanoma skin tumors in the caffeine and exercise group compared to the controls. The size of those tumors also reduced by 85% compared to those of the controls.

The results showed that caffeine or exercise alone also had positive effects, but to a lesser extent compared with caffeine and exercise combined.

Compared to controls (no caffeine, no exercise), there was a 27% reduction in tumor activity with a 61% reduction in tumor volume in the caffeine without exercise group; and a 35% reduction in tumor activity with 70% reduction in tumor size, in the exercise without caffeine group.

In a further set of experiments, the researchers fed mice on a high-fat diet rich in omega-6 fatty acids, and looked at the effects of the caffeine with and without exercise treatments.

They found that the caffeine plus exercise group showed a large reduction in fat and an over 90% drop in levels of inflammatory markers. Development and size of cancer also dropped.

The researchers suggest there is a link between fat, inflammation and cancer. Fat tissue secretes inflammatory compounds, so less fat means less inflammation. Inflammation has been linked to increased risk of skin cancer, said Lu.

The National Institutes of Health helped fund the research.

Written by Catharine Paddock PhD