Effects Of Quenching Thirst Versus Full-Fluid Replenishment On Mood And Cognitive Changes After Mild-Hypohydration

Abstract

Comparing cumulative urine output relative to that elicited by water facilitates a comparison of the short-term hydration properties of beverages. This metric of fluid retention is termed the beverage hydration index (BHI). PURPOSE: To determine the additive effect of electrolytes with either carbohydrate or protein to beverages on BHI. METHODS: Seventeen healthy young adult women and men completed four beverage test sessions in randomized order: deionized water (W), electrolytes only (E), carbohydrate-electrolytes (C+E), and 2 g/L dipeptide (alanyl-glutamine)-electrolytes (AG+E). [Electrolyte] (Na + 19 mmol, K + 3 mmol) were equivalent across all beverages except W. Subjects reported at 0700 h following an overnight fast and a standardized hydration protocol as previously described. One liter of each beverage was consumed over 30 min, metered at 7.5 min intervals. Cumulative urine output, body mass and urine osmolality were obtained every 60 min through 240 min. Beverage palatability was assessed with visual analog scales. RESULTS: Compared to W, BHI was significantly (P < .05) higher for C+E at 120 min (1.15 ± 0.17) while BHI for E (1.12 ±0.25) and AG+E (1.10 ± 0.24) were not different (P > .05). BHI for AG+E (1.15 ± 0.20) was higher than W later at 240 min. No test beverages differed in BHI from each other at any time point; however, net fluid balance was lower (by 134 g) at 60 min with AG+E vs. C+E. AG+E elicited a higher overall urine osmolality by 127 mosmol/kg vs. W (268±25 mosmol/kg). Palatability scores for taste were lower for W vs. other beverages and stomach bloating higher for W vs. C+E and AG+E. CONCLUSIONS: The addition of electrolytes (in ranges typically found in sports drinks) to water did not significantly improve fluid retention. Compared to water, the timeline for improved fluid retention occurs earlier for carbohydrate sports drink than a protein beverage with similar electrolyte levels. However, there was no meaningful difference among drinks in hydration status when [electrolyte] were equivalent.