Caffeine: Is it dehydrating or not?

I've been seeing ads that say cola and coffee drinks hydrate you as well as water does. Is this true?

- Albert / Ohio

Answer

It is true. Researchers used to believe that caffeinated drinks, even consumed in moderate amounts, had a diuretic effect. This means that you would urinate more after drinking them and become dehydrated. Recent research shows that this is not true, and caffeine only has a diuretic effect if you consume large amounts of it — more than 500 to 600 milligrams a day.

Still, caffeinated drinks can make you jittery, sleepless or anxious. Water is probably your best bet to stay hydrated. It's calorie-free, caffeine-free, inexpensive and readily available.

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