For years, health care professionals and athletic trainers have warned people that caffeine has a diuretic effect and can cause frequent urination. As caffeinated soft drinks and energy drinks became popular, those warnings were extended to include them. Now, based on new research, it seems that the warnings may have been unfounded.
Kidneys and Diuretics
The kidneys are the body organs responsible for helping to keep the blood clean and chemically balanced. Each day, a person's kidneys filter and process about 200 qts. of blood, removing approximately 2 qts. of water and waste products. The waste and excess water become urine. A variety of substances can cause the kidneys to release more water than normal; this is called a diuretic effect. If too much water is excreted, the body can become dehydrated, or the chemical balance in the blood can be upset. Water, cranberry juice and alcohol are known to be weak diuretics.
Caffeine as a Diuretic
Caffeine is the active substance in coffee and sodas that has been implicated as a diuretic. R. J. Maughan and J. Griffin reviewed the research literature published on this subject between January 1966 and March 2002. They reported in the December 2003 issue of the "Journal of Human Nutrition and Dietetics" that while drinking two to three cups of coffee or five to eight cups of tea in a short time could cause a short-term increase in urine output for people who had not had any caffeine for a period of days or weeks, the amount of caffeine in standard servings of coffee, tea or soda did not appear to have any diuretic action.
High Doses of Caffeine
Higher amounts of caffeine, however, can have a diuretic effect. According to Katherine Zeratsky, a registered dietician at the Mayo Clinic, you would need to drink four to seven cups of coffee to get the necessary dose of caffeine --- about 500 to 600 mg. And Lawrence E. Armstrong, who has researched this issue extensively at the University of Connecticut, says that 20 to 30 percent of Americans ingest more than 600 mg of caffeine a day. But according to Armstrong, all of the studies on caffeine as a diuretic show that less than 226 mg of caffeine --- approximately one to four cups of brewed coffee --- do not show a diuretic effect, and even doses of up to 553 mg do not show any difference.
Considerations and Warnings
While coffee and sodas may not cause excess or frequent urination, Zeratsky points out that they can cause sleeplessness and anxiety or make you jittery. In addition, many soft drinks contain sugar, and unless you drink your coffee black, it can also add calories or fat to your diet. She recommends water as the best choice for hydration.
References
- National Kidney and Urologic Diseases Information Clearinghouse; The Kidneys and How They Work
- "Exercise and Sport Sciences Reviews "; Caffeine, Fluid-Electrolyte Balance, Temperature Regulation, and Exercise-Heat Tolerance; Lawrence E. Armstrong; Douglas J. Casa; Carl M. Maresh; Matthew S. Ganio; July 2007
- MayoClinic.com; Nutrition and Healthy eating; Caffeine: Is it dehydrating or not? Katherine Zeratsky, R.D., L.D.; August 2009
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