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

Answers from Katherine Zeratsky, R.D., L.D.

It is true that caffeinated fluids can contribute to your daily fluid requirement.

Drinking caffeine-containing beverages as part of a normal lifestyle doesn't cause fluid loss in excess of the volume ingested. While caffeinated drinks may have a mild diuretic effect — meaning that they may cause the need to urinate — they don't appear to increase the risk of dehydration.

Still, caffeinated drinks can cause headaches and insomnia in some people. Water is probably your best bet to stay hydrated. It's calorie-free, caffeine-free, inexpensive and readily available.

Aug. 20, 2011 See more Expert Answers