The Beverage Hydration Index: Influence of Electrolytes, Carbohydrate and Protein

Abstract

The beverage hydration index (BHI) facilitates a comparison of relative hydration properties of beverages using water as the standard. The additive effects of electrolytes, carbohydrate, and protein on rehydration were assessed using BHI. Nineteen healthy young adults completed four 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). One liter of beverage was consumed, after which urine and body mass were obtained every 60 min through 240 min. Compared to W, BHI was higher (p = 0.007) for C + E (1.15 ± 0.17) after 120 min and for AG + E (p = 0.021) at 240 min (1.15 ± 0.20). BHI did not differ (p > 0.05) among E, C + E, or AG + E; however, E contributed the greatest absolute net effect (>12%) on BHI relative to W. Net fluid balance was lower for W (p = 0.048) compared to C + E and AG + E after 120 min. AG + E and E elicited higher (p < 0.001) overall urine osmolality vs. W. W also elicited greater reports of stomach bloating (p = 0.02) compared to AG + E and C + E. The addition of electrolytes alone (in the range of sports drinks) did not consistently improve BHI versus water; however, the combination with carbohydrate or dipeptides increased fluid retention, although this occurred earlier for the sports drink than the dipeptide beverage. Electrolyte content appears to make the largest contribution in hydration properties of beverages for young adults when consumed at rest.

Keywords: dipeptide; fluid balance; osmolality; potassium; sodium; sports drink.

Figure 1

Schematic of the Beverage Hydration Index test protocol performed for each beverage trial (n = 4).

Figure 2

Box and whisker plot for beverage hydration index (BHI) at 120 min (TOP panel A) and 240 min (BOTTOM panel B) for test beverages and water (note: water is 1.0 standard). X = mean values connected by line across beverages; horizontal line = median value. * Carbohydrate-electrolyte (C + E) higher (p < 0.05) vs. Water; ‡ dipeptide-electrolyte (AG + E) higher (p < 0.05) vs. Water.

Figure 3

Individual subject data illustrating the net change in Beverage Hydration Index (BHI) relative to water (versus electrolytes) in Panel A; relative to electrolyte base solution (versus carbohydrate added) in Panel B and relative to electrolyte base solution (versus dipeptide added) in Panel C at 120 min (left columns) and 240 min (right columns).

Figure 4

Mean (±SD) net fluid balance (A) and mean (±SD) cumulative urine mass (B) over 240 min based on beverages W (water); E (electrolyte); C + E (carbohydrate + electrolyte); and AG + E (dipeptide+ electrolyte). * Difference between W vs. C + E; † between AG + E vs. C + E; ‡ between W vs. AG + E (p < 0.05).

Figure 5

Mean (±SD) urine osmolality (UOsm) over time denoting significant differences between beverages. ‡ Difference between dipeptide-electrolyte (AG + E) vs. water (W); * Electrolyte (E) vs. W; † AG + E vs. carbohydrate-electrolyte (C + E) (p < 0.05).

Figure 6

Mean (±SD) visual analog scale (VAS) ratings for stomach bloating after ingesting 1 L of beverages: W, water; E, electrolyte drink; C + E, carbohydrate-electrolyte sports drink; AG + E, dipeptide-electrolyte drink. * Difference (p < 0.02) for W at 60, 180, and 240 min compared to immediately after ingestion (0 min).