Does Drinking Coffee Dehydrate You?
People have long been warned that drinking too much coffee will cause dehydration. But research suggests there's little truth to that claim: one 2014 study found that caffeine had no effect on the hydration status of 50 subjects who drank coffee as their primary drink, and drank water in the experiment's second phase. Another study found that coffee did not dehydrate tired athletes who drank it during practice. Though caffeine does have a diuretic effect, it isn't strong enough to cause the body to excrete more liquid than it's taking in. What's more, habitual coffee drinkers will find that this diuretic effect diminishes as their system becomes accustomed to the caffeine.
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from Mental Floss
Key Facts In This Video
One typically sized serving of espresso contains less caffeine than a cup of coffee. (0:35)
Although ingesting caffeine does provide a metabolism boost, it is not a surefire way to lose weight. (2:17)
Caffeine withdrawal is very real, but caffeine is not considered addictive. (3:22)