• image.alt
  • With Mayo Clinic nutritionist

    Katherine Zeratsky, R.D., L.D.

    read biography

Mayo Clinic Health Manager

Get free personalized health guidance for you and your family.

Get Started

Free

E-Newsletter

Subscribe to receive the latest updates on health topics. View sample

Question

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?

Answer

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

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.

Next question
Food poisoning: How long can you safely keep leftovers?

AN01661

Aug. 21, 2007

© 1998-2009 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.com," "EmbodyHealth," "Reliable tools for healthier lives," "Enhance your life," and the triple-shield Mayo Clinic logo are trademarks of Mayo Foundation for Medical Education and Research.

Print Share Reprints

Text Size: smaller largerlarger