Moderate coffee consumption 'not linked' to dehydration

Researchers have dispelled the myth that coffee consumption can cause dehydration, as they have found that drinking moderate amounts of coffee does not result in dehydration and contributes to daily fluid requirements in regular coffee drinkers just as other fluids do.

New study by the researchers at the University of Birmingham School of Sport and Exercise Sciences, UK, is the first study to directly assess the effects of a moderate consumption of coffee compared to equal volumes of water.

"Despite a lack of scientific evidence, it is a common belief that coffee consumption can lead to dehydration and should be avoided, or reduced, in order to maintain a healthy fluid balance. Our research aimed to establish if regular coffee consumption, under normal living conditions, is detrimental to the drinker's hydration status," lead author of the study, Sophie Killer, said.

In a sample of regular coffee drinkers, Killer and colleagues measured the effects of moderate consumption of black coffee compared to the consumption of equal volumes of water on fluid balance and hydration status.

Fifty male participants were tested in two phases, where they were required to drink four mugs (200ml) of either black coffee or water per day for three days. In the second phase, those who had initially drunk coffee switched to water and vice versa. The two phases were separated by a ten day 'wash out' period.

The researchers found no significant differences in total body water or any of the blood measures of hydration status between those who drank coffee and those who drank water.

Furthermore, no differences in 24-hour urine volume or urine concentration were observed between the two groups.

The study is published in the journal PLOS ONE.