Tulare County

Most nutritionists recommend drinking eight glasses of water per day in order to maintain proper hydration status and good health in general. While some agree with this advice, others feel that it is excessive, and that fluids other than water are just as effective. When in doubt, professionals turn to current research for the best answer. A recent ten year study by the Harvard School of Public Health concerned fluid intake and the risk of bladder cancer in men. The study hypothesized that increased fluid intake may reduce the exposure to carcinogens by diluting the urine and by increasing the frequency of urination.

Bladder cancer is the fourth leading type of cancer among men in the United States. Women, on the other hand, have only about one-fourth the incidence of this type of cancer as compared to men. In 1996, nearly 310,000 cases were diagnosed worldwide. American men, consequently, want to know what they can do to decrease their risk. Studies that have looked at the influence of different types of fluids like alcohol, coffee, and chlorinated water on bladder cancer risk have produced inconsistent results. The Harvard study attempts to clarify some of these results.

The study population consisted of 47,909 participants of the prospective Health Professionals Follow-up Study. Fluid intake was determined using a food frequency questionnaire (FFQ) that included 22 types of beverages. Participants completed the FFQ in 1986, 1990, and 1994.

A total of 252 cases of bladder cancer were newly diagnosed in the ten-year follow-up period. All cases during the first three years were excluded so that the possibility of subjects with preclinical disease would not influence the findings. Age and smoking were both found to be strongly associated with cancer of this type.

The investigators found that, after adjusting for age and smoking, the risk of bladder cancer decreased as total fluid intake increased. They also found that water was the only beverage that showed a statistically significant association with the risk of bladder cancer. Water intake of six or more cups daily was associated with a 51% reduction in bladder cancer risk compared to subjects drinking less than one cup per day. However, the FFQ used in this study didn't identify the type and source of water consumed (i.e., tap, bottled, or filtered). Therefore, the researchers were not able to study the effect of drinking water source on the risk of bladder cancer.

It appears that smokers, especially heavy smokers, stand to benefit the most from increased fluid intake. Smokers can have high urine levels of tobacco-related carcinogens, and a three- to fivefold increased risk of bladder cancer. However, a basic principle of nutrition holds that increasing water and fluid consumption improves hydration status and health in general. This study, then, tends to support the recommendation to drink eight glasses of water daily.

Source: eFOOD RAP on the Web at: http://www.cfs.purdue.edu/extension/efr/efrframe.htm Summarized from: Can a Low Fluid Intake Increase Your Risk of Bladder Cancer?, Nutrition Research Newsletter Volume XVIII, Number 6, June 1999.