Post-Exercise Rehydration: Effect of Consumption of Beer with Varying Alcohol Content on Fluid Balance after Mild Dehydration.
Level 2 - randomized trial
Individual randomized crossover trial in humans
PubMed 27800480 · doi:10.3389/fnut.2016.00045
What was done
Eleven healthy males (age 24.5 ± 4.7 years, body weight 75.4 ± 3.3 kg, VO2max 58.3 ± 6.4 mL/kg/min) exercised on a cycle ergometer for 45 minutes at 60% of maximal power output until reaching mild dehydration (1% body mass loss). In a crossover design, participants consumed in random order one of five test beverages in an amount equal to 100% of sweat loss: non-alcoholic beer (0.0%), low-alcohol beer (2.0%), full-strength beer (5.0%), an isotonic sports drink, and water. Fluid balance was tracked for 5 hours post-rehydration.
What was found
After 1 hour, urine production was significantly higher for 5% beer compared to the isotonic sports drink (299 ± 143 vs. 105 ± 67 mL; p < 0.01). At the end of the 5-hour period, net fluid balance remained negative across all conditions (p = 0.681). Fluid retention percentages did not differ significantly among beverages (p = 0.460): 42% for isotonic sports drink, 36% for non-alcoholic beer, 36% for low-alcoholic beer, 34% for water, and 21% for 5% beer. Replacing 100% of body mass loss was insufficient to achieve complete rehydration across all conditions.
Why it matters
Non-alcoholic and low-alcohol beers yield fluid retention rates comparable to water and sports drinks after mild exercise-induced dehydration, whereas 5% beer causes a transient early increase in urine output. It also reinforces that replacing only 100% of fluid loss is inadequate to restore full fluid balance.
Limits
The study had a very small sample size (11 participants) and was restricted entirely to young, healthy males. Dehydration was mild (1% body mass loss), leaving fluid retention after greater dehydration unexamined.
Cited by
- supports Post-exercise alcohol consumption impairs rehydration only at doses around 1 g/kg body weight, but not at doses below 0.5 g/kg.