Intestinal fluid absorption during exercise: role of sport drink osmolality and [Na+]

Med Sci Sports Exerc. 2001 Jun;33(6):907-15. doi: 10.1097/00005768-200106000-00009.


The purpose of this study was to evaluate the effects of modifying the osmolality and [Na+] of orally ingested rehydration beverages during exercise on intestinal absorption in the duodenum and upper jejunum. Six subjects randomly ingested (23 BW) the following 6% carbohydrate solutions with and without Na+ during 85-min of cycle exercise (65% VO2 peak) in a cool (22 degrees C, 40% RH) environment: a) 0 Na+, 245; b) 20 mEq Na+, 283; c) 20 mEq Na+, 169; d) 50 mEq Na+, 275; and e) 50 mEq Na+, 176 To alter solution osmolality and maintain carbohydrate concentration constant, glucose, sucrose, fructose, and maltodextrin were used in different combinations. Nasogastric and multilumen tubes were fluoroscopically placed in the stomach and intestine, respectively, to simultaneously determine gastric emptying and intestinal absorption as previously described (Lambert et al., Int. J. Sports Med.17:48, 1996). Gastric emptying was not different among solutions and averaged 13 +/- 0.5 mL.min-1. Net fluid absorption was not different among beverages nor between duodenum and jejunum (x = 10.8 +/- 1.6 and 7.9 +/- 1.1, respectively). Mean osmolality increased significantly (P < 0.05) from the duodenum to the jejunum (242 +/- 6 and 293 +/- 7, respectively) but did not differ among solutions. These data provide evidence that a hypotonic 6% carbohydrate beverage with 50 mEq.L-1 Na+ did not enhance intestinal fluid absorption or attenuate the decline in plasma volume during exercise more than an isotonic carbohydrate-electrolyte solution or a hypotonic carbohydrate solution without sodium.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Carbohydrate Metabolism
  • Electrolytes
  • Exercise / physiology*
  • Female
  • Gastric Emptying*
  • Humans
  • Intestinal Absorption*
  • Male
  • Osmolar Concentration
  • Sodium / pharmacokinetics*
  • Water-Electrolyte Balance


  • Electrolytes
  • Sodium