Fact Or Fiction: Coffee Makes You Dehydrated

If you drink large amounts of coffee, you've no doubt encountered some "concerned citizens" — aka, coffee haters — who worry that you're doing all kinds of harm to your body by slinging back brew like there's no tomorrow. And indeed, some of those concerns are valid. Drinking more than six coffees per day is linked to heart disease, and too much caffeine can interfere with your sleep. One other very common callout you'll hear, as you top off your mug, is that you're going to dehydrate yourself from all of that caffeine. But does this claim actually hold water?

A recent study by the UK's University of Birmingham compared the hydration levels of subjects who got their fluids mainly from coffee to how hydrated they were when they drank water instead. There was no significant difference in their hydration status, whether they guzzled agua or java. "Caffeine really had absolutely no influence on hydration status," concluded Douglas Casa of the University of Connecticut, reviewing this study for NPR.

Not only does coffee not make you dehydrated, but there's actually a lot of water in that mug o' joe. "Coffee counts toward your daily water intake," registered dietitian Lauren Elliott told Sharp. "The best way to hydrate is always to drink water, but coffee lovers can definitely count their coffee toward their eight daily cups of fluid." Note that Elliott said you can count it towards your fluid intake — what you won't want to do is completely swap out your H20 for coffee, as tempting as that might be. "The sugar and fat from cream and sweetened coffee drinks, however, can lead to weight gain and other detrimental health effects," she explained. 

Just to be on the safe side, though, pay attention to your body. If you're showing any signs of dehydration — particularly if you're working up a sweat at the gym — it can't hurt to add a cup of plain water in between those coffee refills. "If you notice you're not performing as well in the gym, experiencing muscle cramps, or lacking overall energy during your workouts, you may want to cut back a little on the bean juice, or drink two or three more cups of water or low-calorie beverages throughout the day," advised BodyBuilding's science editor, Krissy Kendall, Ph.D.