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- 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.
- 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
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