Medicine & Science in Sports & Exercise:
C-33 Free Communication/Poster - Hydration Status and Rehydration: MAY 28, 2009 7:30 AM - 12:30 PM ROOM: Hall 4F
Tippet, Melissa L.; Osterberg, Kristin L.; Horswill, Craig A.; Shi, Xiaocai FACSM
Gatorade Sports Science Institute, Gatorade R&D, Barrington, IL.
(M.L. Tippet, PepsiCo, Salary.)
To be an effective fluid replacement beverage during activity, a beverage must provide enough energy to sustain performance and yet be absorbed rapidly in the small intestine. Although the effect of carbohydrate (CHO) on fluid absorption is well-established, the interactive impact of sodium and CHO concentrations and the effect of pH on fluid absorption are still not clear.
PURPOSE: To determine the effects of different levels of sodium content at two different CHO concentrations on water absorption. Secondarily, we compared the effect of pH on water flux.
METHODS: Seven male subjects were perfused with six beverages (60 min per beverage) at a rate of 15 ml/min in a randomized order using the triple lumen perfusion technique. Water absorption from each solution was calculated based on changes of polyethylene glycol (PEG) concentration in the intestinal samples. Test beverages included water (W, pH = 7), a flavored water placebo (WP, pH = 3), a 3% CHO (sucrose and dextrose) solution with either 18 mEq sodium (LCLS) or 72 mEq sodium (LCHS), and a 6% CHO (sucrose and dextrose) solution with either 18 mEq sodium (HCLS) or 72 mEq sodium (HCHS). Beverage osmolality ranged from 0 to 381 mOsm/kg. A two-factor repeated measures ANOVA was used to determine the significance in water flux (a=0.05).
RESULTS: CHO concentration ranging from 0 up to 6% did not significantly affect mean water flux (-19.7 ± 3.6, -16.3 ± 2.6, and -14.0 ± 0.9 ml·cm-1·h-1 for W, LCLS, and HCLS, respectively) over the 60 minutes of perfusion. Likewise, the sodium content at either CHO concentration did not affect water flux (-12.2 ± 1.2 and -10.7 ± 1.0 ml·cm-1·h-1 for LCHS and HCHS, respectively). Finally, there was no significant difference in water flux based on pH (W: -19.7 ± 3.6 ml·cm-1·h-1 vs. WP: -14.0 ± 2.7 ml·cm-1·h-1).
CONCLUSIONS: Increasing the sodium content to 72 mEq in either a 3% or a 6% CHO solution did not facilitate the rate of intestinal fluid absorption. In addition, a decrease of beverage pH from 7 to 3 did not appear to significantly influence intestinal absorption of fluid.