Can coffee protect smokers against bladder cancer?

Study draws criticism

December 13, 2000
Web posted at: 2:34 p.m. EST (1934 GMT)

From staff and wire reports

(CNN) -- Caffeine and cigarettes are among the human population's two biggest vices. But a new study, which has drawn fire from health experts, suggests that drinking coffee might protect smokers from bladder cancer.

"It sounds a little bizarre," said Dr. Annie Sasco, chief of epidemiology for cancer prevention at the International Agency for Research on Cancer, part of the World Health Organization. Sasco and others said examining the protective effects of coffee's components is an interesting hypothesis, but one that needs further testing before any real confidence can be placed in the theory.

At issue is a preliminary research paper, published this week in the London-based Journal of Epidemiology and Community Health, which found that bladder cancer was about half as likely to occur in smokers who regularly drank coffee as in smokers who did not.

"This could suggest that the coffee consumption modifies the effect of tobacco smoking," said Dr. Gonzalo Lopez-Abente of the Carlos III Health Institute in Madrid, Spain, who led the study.

But he added: "Do not smoke. I think it is dangerous to see coffee consumption as a preventive habit."

Smoking is recognized as the most important cause of bladder cancer. Experts estimate that about 50 percent of these cancers in men and 30 percent in women are due to smoking.

Cigarette use increases the risk for bladder cancer by two to five times and, when smokers quit, their risk declines in two to four years, according to the U.S. National Cancer Institute.

The Spanish study involved 497 people with bladder cancer who were compared with 1,100 people without the disease. They were all asked about their smoking and coffee-drinking habits. Those who drank less than two cups of coffee a week were classified as non-coffee drinkers.

Their researchers found that smokers who drank coffee were three times as likely to develop bladder cancer as non-smoking coffee drinkers. Smokers who didn't drink coffee, however, were seven times as likely to get the disease as non-smokers.

"We have found that the probability of bladder cancer was higher in smokers that do not drink coffee," explained Lopez-Abente.

The scientists are not sure how the protective effect of coffee would work on smokers but they suggested it could somehow reduce toxicity.

Experts not connected with the research had mixed reactions to the main finding, ranging from the view that it highlights the often-unexpected protective effects of substances found in food to the opinion that the theory is fatally flawed by the study's methodology.

Sasco said she was not impressed with how the study compiled its coffee-intake frame of reference. She also didn't like the way researchers omitted important references to "potential other sources of caffeine, such as tea and Coca-Cola."

Coffee contains caffeine, a mild stimulant also found in other popular drinks. But research into a possible link between caffeine and decaffeinated drinks has proven inconclusive, according to the National Cancer Institute.

The Associated Press and Reuters contributed to this report.

Dietitians look at health effects of coffee
October 21, 1999
Drinking fluids reduces bladder cancer risk, study finds
May 5, 1999
Conference examines link between cancer and diet
April 19, 1999

Journal of Epidemiology and Community Health
National Cancer Institute

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