Does Coffee Cause Dehydration?

Coffee has long been considered a culprit in dehydration but this may be less straight forward than we thought.

Coffee has long been considered a culprit in dehydration because caffeine has a mild diuretic effect. But recent studies have shown that while the caffeine in coffee does increase urination, that increased urination does not counteract the main ingredient in brewed coffee —— WATER.

One study found that consumption of 300 mg of caffeine which is the equivalent of 3 cups of coffee (710 ml) resulted in increased urine production of only 109 ml (1).

In order to see a significant diuretic effect from coffee, it would require the consumption of 5 or more cups of brewed coffee at once (2).

Sources:

  1. Coffee with High but Not Low Caffeine Content Augments Fluid and Electrolyte Excretion at Rest
  2. No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population