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Fluid balance

Fluid balance: Factsheet

Water makes up about sixty percent of body weight. As every system in the body depends on the availability of fluids, even mild dehydration can impair bodily functions and performance.
January 1, 2015

Fluid requirements vary greatly between individuals and can alter with climate and physical activity levels. Recommendations on specific fluid choices also vary between countries.

Coffee, caffeine and fluid balance

  • It is commonly reported that drinking caffeinated coffee can lead to dehydration. Recent scientific evidence, however, does not support this commonly held belief.
  • Coffee drinking in moderation contributes to our fluid intake and does not lead to dehydration or significant loss of body water1,2,3,4.
  • Whilst caffeine may have a small diuretic effect, this effect is not strong enough to counter-balance the benefits of fluid intake from coffee drinking. Black coffee contains more than 95% water.
  • During exercise, the evidence shows that, not only is moderate caffeine intake beneficial for endurance performance, it does not contribute to body dehydration5,6.
  • Advice to abstain from drinking moderate amounts of caffeinated coffee in order to maintain adequate fluid balance is unfounded.


  1. Kolasa K.M. et al. (2009) Hydration and health promotion. Nutrition Today. 44:190-203
  2. Popkin B.M. et al. (2006) A new proposed guidance system for beverage consumption in the United States. American Journal of Clinical Nutrition, 83, 529-542
  3. Silva A. M. et al. (2013) Total body water and its compartments are not affected by ingesting a moderate dose of caffeine in healthy young adult males. Applied Physiology Nutrition & Metabolism, 38:626-632.
  4. Killer S. C. et al. (2014) No Evidence of Dehydration with Moderate Daily Coffee Intake: A Counterbalanced Cross-Over Study in a Free-Living Population. PLoS ONE, 9(1): e84154.
  5. Ganio M.S. et al. (2009) Effect of caffeine on sport-specific endurance performance: a systematic review. Journal of Strength and Conditioning Research, 23(1):315-24.
  6. Goldstein E.R. et al. (2010) Caffeine enhances upper body strength in resistance trained athletes. Journal of the International Society of Sports Nutrition, 7 :5