Rumour has long been around that caffeinated coffee consumption leads to dehydration and that coffee drinking needs to be limited to reduce this ‘detrimental’ effect on hydration status. However research has proved otherwise.

One study compared the effects of caffeinated coffee consumption against water consumption in 50 male coffee drinkers. The participants completed two trials where they consumed either 4 mugs (200ml) black coffee or water per day over the course of three consecutive days. Physical activity, food and fluid intake was controlled throughout the study and markers of hydration (including urine and blood analysis), and body mass were recorded daily, with total body water being calculated pre- and post-trial.

They found no significant difference in hydration status between conditions, suggesting that coffee consumed in moderation by habituated males may have a similar hydrating effect to water. Although large doses of caffeine has been linked to an acute diuretic effect, researchers believe that regular caffeine consumption may lead to a tolerance against this effect.

However, females were excluded from the study due to the effect of the menstrual cycle on fluid balance, the study did not include anyone over the age of 46 and it did not investigate the effects on those who are not habitual coffee drinkers. Therefore whilst this study provides insightful findings into the effects of moderate coffee drinking on hydration status for male adults who regularly consume coffee, there is still limited research in the area, and more research is required to cover its effects on other populations.

Adie Blanchard – Researcher

Reference

Killer, S. C., Blannin, A. K., & Jeukendrup, A. E. (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.