Coffee and the dehydration myth

Happy National Coffee Day

Enjoy that cup of joe, athletes. Research published January 9, 2014 in PLOS ONE, the Public Library of Science open access peer reviewed scientific journal by researchers in the School of Sport and Exercise Sciences, University of Birmingham, UK suggests coffee doesn’t dehydrate you.

It is often suggested that coffee causes dehydration and its consumption should be avoided or significantly reduced to maintain fluid balance. The aim of this study was to directly compare the effects of coffee consumption against water ingestion across a range of validated hydration assessment techniques. In a counterbalanced cross-over design, 50 male coffee drinkers (habitually consuming 3–6 cups per day) …

If you want to read the details of the study, click here, but here’s the important bit:

Our data show that there were no significant differences across a wide range of haematological and urinary markers of hydration status between trials. These data suggest that coffee, when consumed in moderation by caffeine habituated males provides similar hydrating qualities to water.

Does anybody know if there’s such a thing as a French press that fits in a bicycle water bottle?

This is apparently one of the myths covered in this book on the human body and health, which was published in 2009.

Via the Incidental Economist.


  1. I saw this right after it was released and every time I have seen it covered everyone (including you Richard) only focuses on the dehydration myth, ignoring all the valid health concerns still associated with coffee. I’m still drinking coffee, the health concerns don’t bother me much, what bothers me more is the Internet seeing this article and saying, “okay cool coffee is totally healthy.” It’s like when a study came out last year showing increased algal blooms leading to more dead algae on the abyssal plane and everyone jumped on this, “OH MY GOD IT’S FUKUSHIMA” bandwagon (it’s not). In the spirit of perpetuating the whole of science rather than a microcosm (this one study) let me provide some more links to still substantiated negatives.

    Glad it doesn’t dehydrate you as well as give you the runs, though having the runs can dehydrate you (as anyone who has had food poisoning can attest).

    Caffeine alters our brains adenosine receptors, replacing adenosine with caffeine over time. “adaptive changes and lead to chronic alterations of receptor expression and availability,”

    This site has a pretty good run down of the negatives:

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