Health Canada researchers made headlines yesterday, across Canada and around the world, on the news that heavy coffee consumption may increase the risk of bladder cancer in men. The news reports – “Study links coffee to bladder cancer” was how the Toronto Star and China’s Xinhua both played it – were unwarranted, even if accurate. The jolt to the story came more from an over-caffeinated press than from the study itself, or from the interview provided by the study’s lead researcher, Anne-Marie Ugnat.Ms. Ugnat did her best to play down this finding of her study, whose main purpose was to discover risks to industrial workers from chemicals in the workplace. The study “is suggestive of a possible relationship (between coffee and cancer) but in no way conclusive,” was as alarmist as she got for the Canadian Press reporter who covered the story. “One would like to do a more detailed study on the topic.”
More details can’t hurt. Especially since Ms. Ugnat’s own study, to its credit, pointed to its many shortcomings, and to robust findings in other studies that throw cold water on her coffee conclusions: “However, a recent systematic literature review has suggested that coffee and tea consumption are probably not associated with bladder cancer,” reported her study, which was published in Chronic Diseases in Canada, a Health Canada periodical. “Coffee drinking has been studied extensively as a potential risk factor, but the inconsistency of the observed associations suggests that the relationship is either quite weak, non-causal, or dependent in a complex way on unmeasured factors.”
In the last 50 years, researchers such as Ms. Ugnat have performed some 19,000 studies into coffee’s effects on health. The last 18,900 of them, over the last 40-odd years, have overwhelmingly given coffee a clean bill of health. In the case of bladder cancer, however, some recent studies have done more, too. They have tended to point to positive health benefits.
A study published in the January, 2001, issue of the London-based Journal of Epidemiology and Community Health indicated that coffee may protect against bladder cancer, especially among smokers. Analyzing data from 500 diagnosed cases of bladder cancer, as well as 1,000 control subjects, Scientific American reported, “the researchers found that non-coffee drinking smokers were seven times more likely to develop the disease as non-smokers. Coffee-drinking smokers, on the other hand, were only three times more at risk. Coffee thus appears to somehow dilute the harmful effect of tobacco use on the bladder. Previous studies have suggested that caffeine might discourage mutations from forming, perhaps by inducing activity in an enzyme known as CYP1A2.”
A 2001 study at Maastricht University in the Netherlands found the link between coffee consumption and bladder cancer to be inconclusive with men, but with women, there was a probable benefit from increasing coffee consumption.
A 2002 study at the University of Calgary’s Department of Community Health Sciences that looked at the effect of coffee on bladder and colon cancer found that coffee did not significantly affect the risk of bladder cancer but that it did affect colon cancer risk – the more coffee a day that was drunk, the lower the risk of colon cancer.
The largest and most detailed study to date to examine coffee consumption’s relationship to bladder cancer was the National Bladder Cancer Study, conducted in the United States in the late 1970s by the National Cancer Institute, in response to the U.S. Food and Drug Administration’s need to determine whether saccharin increased the risk of developing bladder cancer. After interviewing nearly 3,000 cases and 6,000 controls to determine occupational, environmental, medical and lifestyle influences on risk, the study yielded dozens of reports in peer-reviewed journals and found numerous causes of bladder cancer. Coffee was not among them.
Lawrence Solomon is executive director of Urban Renaissance Institute and policy director at Consumer Policy Institute, divisions of Toronto-based Energy Probe Research Foundation, September 10, 2004