March 7, 2008
Does Coffee Make You Dehydrated?
For a long time it has been thought that coffee and other caffeine-containing drinks are dehydrating and don’t count in your daily fluid intake. Actually, some go as far as recommending one cup of water for every cup of Joe you have. Most of us are aware that caffeine is a diuretic (it makes us want to urinate), but does it deprive us of our bodily fluids?
In his study, “Caffeine, Body Fluid-Electrolyte Balance, and Exercise Performance,” Lawrence E. Armstrong, a professor of exercise physiology at the University of Connecticut deals with the belief that caffeinated drinks rob us of our valuable fluids. By investigating the scientific research on the subject, he reaches the conclusion that although caffeine, similarly to water, is a mild diuresis (it increases excretion of urine), moderate caffeine consumption does not lead to a “fluid-electrolyte imbalance” that can influence health or exercise performance. What is more, we retain approximately the same amount of fluid after drinking a caffeinated drink as we do after drinking water.
Even more interesting for notorious coffee consumers is the discovery that those with caffeine tolerance have lower likelihood that a fluid electrolyte imbalance will appear. The more regular your caffeine habit, the more fluid your body is conditioned to retain.
Other discoveries support his claim. A minor study carried out at the University of Nebraska tested the body weight, urine output, and blood of 18 subjects after they drank caffeinated and non-caffeinated drinks. They established that there was “no significant differences in the effect of various combinations of beverages on hydration status of healthy adult males.” The Institute of Medicine expert panel on water and electrolyte intake claims that the diuretic effects of caffeine are temporary, and that coffee, tea, and colas can contribute to overall water intake.