Post-exercise rehydration with beer impairs fluid retention, reaction time, and balance

Abstract

Beer is promoted by the popular media as a good choice for rehydration, but there is limited support for the claim. To assess the effect of beer alcohol on rehydration and motor control, 11 young (24.4 ± 3.7 y.o.) males of legal drinking age were dehydrated to 2.12 ± 0.20%BM (mean ± SD) by exercising in a climatic chamber (31.7 ± 1.6°C, 55.0 ± 8.3% r.h.) on three different days, one week apart, and rehydrated with 100% of their sweat loss using WATER, 4.6% alcohol BEER, or nonalcoholic beer (NAB), in random order. Urine output, blood alcohol content (BAC), reaction time (RT), and balance (VCOP) were measured every 30min over three hours and compared via two-way, repeated-measures ANOVAs. After consuming ≈ 1.6 L in one hour, urine output was greater for BEER (1218 ± 279 mL) than NAB (745 ± 313, p=0.007) and WATER (774 ± 304, p = 0.043). BAC remained at 0 with WATER and NAB; with BEER, the 95%CI was [0.752, 0.963g/L] immediately post-rehydration. RT was longer for BEER (0.314 ± 0.039s) vs NAB (0.294 ± 0.034s, p = 0.009), but no different from WATER (0.293 ± 0.049s, p = 0.077). VCOPx was significantly higher for BEER (0.0284 ± 0.0020 m*s-1) compared with NAB (0.0233 ± 0.0010 m*s-1) or WATER (0.0238 ± 0.0010 m*s-1) (p = 0.022), but VCOPy was not different among beverages. In conclusion, rehydration with BEER resulted in higher diuresis, slower reaction time, and impaired balance, compared with NAB or WATER.