Increasing the number of cups of caffeinated coffee you drink could lower your risk of developing the most common form of skin cancer, basal cell carcinoma, according to a study published in Cancer Research, a journal of the American Association for Cancer Research.

"Our data indicate that the more caffeinated coffee you consume, the lower your risk of developing basal cell carcinoma," said Jiali Han, Ph.D., associate professor at Brigham and Women's Hospital, Harvard Medical School in Boston and Harvard School of Public Health.

"I would not recommend increasing your coffee intake based on these data alone," said Han. "However, our results add basal cell carcinoma to a list of conditions for which risk is decreased with increasing coffee consumption. This list includes conditions with serious negative health consequences such as type 2 diabetes and Parkinson's disease."

Basal cell carcinoma is the form of skin cancer most commonly diagnosed in the United States. Even though it is slow-growing, it causes considerable morbidity and places a burden on health care systems.

"Given the large number of newly diagnosed cases, daily dietary changes having any protective effect may have an impact on public health," said Han.

Han and his colleagues generated their results by conducting a prospective analysis of data from the Nurses' Health Study, a large and long-running study to aid in the investigation of factors influencing women's health, and the Health Professionals Follow-up Study, an analogous study for men.

Of the 112,897 participants included in the analyses, 22,786 developed basal cell carcinoma during the more than 20 years of follow-up in the two studies. An inverse association was observed between all coffee consumption and risk of basal cell carcinoma. Similarly, an inverse association was seen between intake of caffeine from all dietary sources (coffee, tea, cola and chocolate) and risk of basal cell carcinoma. However, consumption of decaffeinated coffee was not associated with a decreased risk of basal cell carcinoma.

"These results really suggest that it is the caffeine in coffee that is responsible for the decreased risk of basal cell carcinoma associated with increasing coffee consumption," said Han. "This would be consistent with published mouse data, which indicate caffeine can block skin tumor formation. However, more studies in different population cohorts and additional mechanistic studies will be needed before we can say this definitively."

In contrast to the findings for basal cell carcinoma, neither coffee consumption nor caffeine intake were inversely associated with the two other forms of skin cancer, squamous cell carcinoma and melanoma, the most deadly form of the disease.

Only 1,953 cases of squamous cell carcinoma and 741 cases of melanoma were recorded among the 112,897 participants included in Han's analyses.

"It is possible that these numbers are insufficient for any association with coffee consumption to be seen," said Han. "As the study participants are followed for a longer time, the number of cases of these conditions is likely to increase. We may be in a position in 10 years' time to better address this issue."