Why Does Coffee Cause Dehydration?

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.

What makes coffee dehydrating?

Coffee contains caffeine, a diuretic compound that can increase urination frequency. That said, it takes drinking large amounts, such as 5 cups of brewed coffee or more at once, for it to have a significant dehydrating effect.

Should you drink coffee when dehydrated?

Yet the study was just the most recent example of research that has debunked the coffee-dehydration myth. In fact, the Institute of Medicine concluded in its 2004 Dietary Reference Indexes report that caffeinated drinks can contribute to daily water needs as well because the diuretic effect is minimal.