Can Caffeine Cause Dehydration?

Unless you're drinking more than 4 cups of coffee or the equivalent amount of caffeine each day, caffeine does not cause dehydration. Several studies led by professor and scientist Lawrence Armstrong disproved the long-standing belief that moderate amounts of caffeine cause dehydration. His studies also proved other caffeine-related facts with regard to athletic performance and the body's fluid-electrolyte balance.

Disproven Theory

The theory used to be that caffeine caused dehydration by acting as a diuretic and increasing your need to urinate. The increased loss of bodily fluids through urination would thus lead to dehydration. While that holds true for large amount of caffeine, or the more than 500 mg you'd get from drinking more than 4 cups of coffee each day, Armstrong notes it also holds true for large amounts of any beverage, including water.

Evidence

In addition to his findings on dehydration, Armstrong's studies uncovered other information with regard to caffeine. There is no evidence caffeine causes an imbalance in the body's fluid and electrolytes, which would bolster another previous theory that drinking caffeine hindered athletic performance. On the contrary, caffeine consumption would have a more dramatic effect on people who were sedentary, since they do not sweat out fluids as frequently as athletes.

Studies

As a scientist researching the fields of human performance and thermoregulation since 1980, Armstrong conducted at least three studies that help support the fact that moderate amounts of caffeine does not lead to dehydration or impair sports performance. Two of the studies appeared in "The International Journal of Sport Nutrition and Exercise Metabolism." The study entitled "Caffeine, Body Fluid-Electrolyte Balance, and Exercise Performance" appeared in the June 2002 issue, while the study "Fluid, Electrolyte, and Renal Indices of Hydration During 11 Days of Controlled Caffeine Consumption" appeared in 2005. "Exercise and Sport Sciences Reviews" published the third study, "Caffeine, Fluid-Electrolyte Balance, Temperature Regulation, and Exercise-Heat Tolerance," in 2007. Each study involved comparing a group of people who consumed a set amount of caffeine with those who consumed a placebo.

Considerations

As with any drug, you can build up a tolerance to caffeine, which means its effects will not be as notable as they would be for someone who rarely consumes it or is sensitive to the substance. The more tolerance you build up, the more resistance you have to its diuretic effects, even when consuming large quantities. Although drinking caffeine does not result in dehydration, it can still lead to nervousness, sleeplessness and anxiety. Coffee is one of the most common beverages containing caffeine, but it's also in certain sodas, colas and teas.