Why Drink More Water?
Drinking Helps Cut Bladder Cancer
By KATHARINE WEBSTER
Associated Press Writer
Drink more water, or coffee, milk, soda, fruit juice, and beer, and you can lower your risk of bladder cancer, a study found.
American men who drank at least 11 8-ounce glasses a day of all liquids cut their risk of two common types of bladder cancer in half, compared with men who drank five glasses or less, the study found.
Water had an independent protective effect. Men who drank at least six glasses of water a day cut their risk of bladder cancer in half, compared with men who had less than one glass, regardless of how much they drank in total liquids.
Bladder cancer strikes an estimated 310,000 people worldwide each year and is the fourth most common cancer among American men. Smokers are more susceptible than non-smokers, and it afflicts four times as many men as women, possibly because few women smoked until recently, and the lag time from when a person starts to smoke to when the cancer shows up can be 40 years or more.
The study in Thursday's New England Journal of Medicine(1999) is the first to demonstrate a clear link between increased liquid intake and decreased bladder cancer of the two types most commonly found in developed countries: papillary and flat transitional cell carcinomas.
The study did not look at a third type, squamous cell carcinoma, which usually is associated with schistosomiasis, a water-borne parasitic disease common in Africa and parts of the Middle East.
No one is certain why drinking more liquids helps prevent the transitional cell cancers. But some researchers believe the bladder lining suffers less exposure to cancer-causing substances in urine when the urine is diluted and urination is more frequent.
Smoking greatly increases the quantity of carcinogens in urine, and this study, like previous research, found that the risk of bladder cancer was nearly four times higher among heavy smokers than it was among non-smokers.
Quitting smoking is the best way to cut your cancer risk, according to the study's lead author, Dominique Michaud, a research fellow at the Harvard School of Public Health. But smokers who can't or won't quit can still cut their cancer risk substantially by drinking more, she said.
The study looked at the eating, drinking, exercise and smoking habits of 47,909 American men from 1986 to early 1996. A similar large-scale study of women does not include enough cases of bladder cancer yet to yield statistically significan results, Michaud said.
In the men's study, 252 developed bladder cancer. The risk increased with age and was higher in the Northeast than in the West.
Besides water, none of the other beverages had an independent beneficial or harmful effect. Although previous, smaller studies had suggested drinking large quantities of coffee or alcohol might be harmful, this study found no increased bladder cancer risk.
Peter Jones, director of the University of Southern California's Norris Comprehensive Cancer Center, said in an accompanying editorial that the study was not sensitive enough to answer questions about whether water quality, especially chlorination, plays a role in cancer risk.
"The quality of what you drink may ... be as important as how
much (or little) you imbibe," he wrote.
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