Caffeine could be a useful addition to sunscreens since it both absorbs ultraviolet light and protects against skin cancer, scientists have said.
A new study has shown how the coffee stimulant acts at the molecular level to prevent sunlight triggering tumour development in the skin.
The findings suggest that "topical application" of caffeine in creams or lotions could help prevent sun-induced skin cancer.
A number of previous studies had already shown that coffee and tea consumption reduced the risk of less serious, non-melanoma, skin cancers caused by exposure to ultraviolet (UV) rays.
In the largest investigation involving 93,676 women, each daily cup of caffeinated coffee was dose-dependently linked to a 5% reduction in skin cancer prevalence.
Decaffeinated coffee had no effect, and tea had a reduced effect consistent with its lower levels of caffeine.
The new research led by Dr Allan Conney, from Rutgers University in New Jersey, US, tested the idea that caffeine interferes with a particular cancer-associated biological pathway.
Caffeine is known to suppress an enzyme, called ATR, that "rescues" stressed or DNA-damaged cells.
Mice genetically engineered to reduce the function of ATR, thus mimicking the effect of caffeine, were found to be far more prone to UV-induced skin cancer.
The findings were published in Proceedings of the National Academy of Sciences.
