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. 2014 Jan 9;9(1):e84154.
doi: 10.1371/journal.pone.0084154. eCollection 2014.

No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population

Sophie C Killer  1 , Andrew K Blannin  1 , Asker E Jeukendrup  1
Affiliations

No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population

Sophie C Killer et al. PLoS One. .

Abstract

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) participated in two trials, each lasting three consecutive days. In addition to controlled physical activity, food and fluid intake, participants consumed either 4×200 mL of coffee containing 4 mg/kg caffeine (C) or water (W). Total body water (TBW) was calculated pre- and post-trial via ingestion of Deuterium Oxide. Urinary and haematological hydration markers were recorded daily in addition to nude body mass measurement (BM). Plasma was analysed for caffeine to confirm compliance. There were no significant changes in TBW from beginning to end of either trial and no differences between trials (51.5±1.4 vs. 51.4±1.3 kg, for C and W, respectively). No differences were observed between trials across any haematological markers or in 24 h urine volume (2409±660 vs. 2428±669 mL, for C and W, respectively), USG, osmolality or creatinine. Mean urinary Na(+) excretion was higher in C than W (p = 0.02). No significant differences in BM were found between conditions, although a small progressive daily fall was observed within both trials (0.4±0.5 kg; p<0.05). 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.

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Conflict of interest statement

Competing Interests: S.C. Killer and A.K. Blannin have declared that no competing interests exist. A.E. Jeukendrup is currently employed by PepsiCo Inc. and is an adjunct Professor at the University of Birmingham. The views expressed here are the views of the authors and not those of PepsiCo Inc. The current employment of Professor Asker Jeukendrup by PepsiCo Inc. does not alter the authors' adherences to all the PLOS ONE policies on sharing data and materials.

Figures

Figure 1
Figure 1. Overview of study design.
Figure 2
Figure 2. Mean total body water estimates from Day 1–Day 3.
n = 25.
Figure 3
Figure 3. Mean body mass.
* Significant difference between days. n = 50.
See this image and copyright information in PMC

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