Caffeinated drinks hydrate almost as well as water

By Marilee Griffin • Published: September 3rd, 2014
Category: Health in a Heartbeat

Like the myth that gum takes seven years to disintegrate in your stomach, there are many old wives’ tales concerning food and drink. But some of them are so ingrained in our social consciousness you may not have second-guesssed them. One such belief is that coffee and tea dehydrate you — and that for each mug of either beverage, you have to drink an extra glass of water.

New research is debunking this widely held food fable. Researchers at the University of Birmingham recently ran a study on 50 coffee drinkers who habitually drink three to six cups per day. In the study, these participants were asked to drink about three-and-a-half cups of coffee a day for three consecutive days, followed by the same amount of water for the same span of time. The participants’ other food and fluid food intake was regulated, as well as their activity levels. By tracking their body mass, total body water, blood and urine levels, the researchers found that coffee was about as hydrating as water.

The notion that caffeinated beverages like coffee and tea dehydrate you stems from the understanding that caffeine is a diuretic — a substance that increases urination. However, drinking caffeinated beverages in moderation doesn’t cause more fluid to exit your body than the beverages provide. The researchers also note that habitual coffee drinkers develop a tolerance to its diuretic effects.

So while the myth is busted — coffee and tea do not cause dehydration — water is still a better source for quenching a thirst. Too much caffeine on a daily basis can sometimes cause jitters, headaches and disrupt sleep, while water is refreshingly caffeine- and calorie-free. However, if you need a little pick-me-up in the middle of the workday, indulge in a caffeinated beverage without worrying about dehydration.