No Evidence of Dehydration With Moderate Daily Coffee Intake: A Counterbalanced Cross-Over Study in a Free-Living Population

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

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Biomarkers / blood
  • Biomarkers / urine
  • Body Water
  • Body Weight
  • Coffee*
  • Cross-Over Studies
  • Dehydration / metabolism*
  • Drinking Behavior*
  • Humans
  • Male
  • Middle Aged
  • Urination
  • Young Adult

Substances

  • Biomarkers
  • Coffee

Grant support

Funding for this study was provided by the Institute for Scientific Information on Coffee (ISIC). ISIC is a non-profit organisation, devoted to the study and disclosure of science related to coffee and health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.