Study reveals coffee has no dehydrating effect

ILLUS-coffee-LisaTheriaultResearchers in Birmingham debunk age old myth.

A new study has found fault in the popular myth of the dehydrating effects of coffee. The study, from the University of Birmingham School of Sport and Exercise Sciences, found that men who regularly drank coffee experience no significant fluctuation in hydration levels.

As counterintuitive as it may seem, coffee for a regular drinker will not cause dehydration. The fifty male participants in the Birmingham study are regular coffee drinkers and were told to follow a strict set of guidelines to prevent excess fluid loss. The participants were not allowed to engage in physical activity or consume alcohol during the study.

Just as the participants’ lifestyle was monitored with care, the researchers measured the levels of hydration closely. Each participant was subjected to multiple tests to determine his fluid loss or gain. With all of the measures in place, coffee was found to be just as hydrating as water for the participants.

“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,” said Sophie Killer, lead author of the study, in a statement. “Our research aimed to establish if regular coffee consumption, under normal living conditions, is detrimental to the drinker’s hydration status.”

It is important to note that these participants were selected based on their coffee consumption. All of the participants drank between three to six cups of coffee per day. As coffee consumption becomes integrated into regular day-to-day life, the body processes it in a different manner.  

A previous study concluded that coffee has dehydrating effects, leading to the myth. The previous study looked at the effect of coffee after the participants abstained from the beverage for a period of five days. It was found that the effect of coffee began to reverse in as little as four days. The issue was that these researchers were using participants who were not regular coffee consumers, leading them to believe that coffee caused dehydration.

Other studies have looked at the effect of caffeine on the body. The problem with these studies is that coffee and caffeine are not equivalent. Coffee contains caffeine, but is not entirely made up of caffeine. There are too many variables present in coffee to say whether coffee is dehydrating based on the effect caffeine has. For this reason the dehydration effect of a smaller more potent caffeinated beverage cannot be ruled out. With coffee, there is enough water to balance out any dehydration. The same cannot be said for a beverage that has a higher caffeine-to-water ratio.

So as long as that caffeinated beverage is a coffee, you can ignore the myth and keep sipping your cup of joe.

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