Effect of beverage osmolality on intestinal fluid absorption during exercise

Abstract

To determine how osmolality of an orally ingested fluid-replacement beverage would alter intestinal fluid absorption from the duodenum and/or jejunum during 85 min of cycle exercise (63.3 +/- 0.9% peak O2 uptake) in a cool environment (22 degreesC), seven subjects (5 men, 2 women, peak O2 uptake = 54.5 +/- 3.8 ml . kg-1 . min-1) participated in four experiments separated by 1 wk in which they ingested a water placebo (WP) or one of three 6% carbohydrate (CHO) beverages formulated to give mean osmolalities of 197, 295, or 414 mosmol/kgH2O. CHO solutions also contained 17-18 meq Na+ and 3.2 meq K+. Nasogastric and multilumen tubes were fluoroscopically positioned in the gastric antrum and duodenojejunum, respectively. Subjects ingested a total of 23 ml/kg body mass of the test solution, 20% (370 +/- 9 ml) of this volume 5 min before exercise and 10% (185 +/- 4 ml) every 10 min thereafter. By using the rate of gastric emptying as the rate of intestinal perfusion (G. P. Lambert, R. T. Chang, D. Joensen, X. Shi, R. W. Summers, H. P. Schedl, and C. V. Gisolfi. Int. J. Sports Med. 17: 48-55, 1996), intestinal absorption was determined by segmental perfusion from the duodenum (0-25 cm) and jejunum (25-50 cm). There were no differences (P > 0.05) in gastric emptying (mean 18.1 +/- 1.3 ml/min) or total fluid absorption (802 +/- 109, 650 +/- 52, 674 +/- 62, and 633 +/- 74 ml . 50 cm-1 . h-1 for WP, hypo-, iso-, and hypertonic solutions, respectively) among beverages; but WP was absorbed faster (P < 0.05) from the duodenum than in the jejunum. Of the total volume of fluid ingested, 82 +/- 14, 74 +/- 6, 76 +/- 5, and 68 +/- 7% were absorbed for WP, hypo-, iso-, and hypertonic beverages, respectively. There were no differences in urine production or percent change in plasma volume among solutions. We conclude that total fluid absorption of 6% CHO-electrolyte beverages from the duodenojejunum during exercise, within the osmotic range studied, is not different from WP.

Characterization of the Human Upper Gastrointestinal Contents Under Conditions Simulating Bioavailability/Bioequivalence Studies

“…Data are in accordance with those reported by Gisolfi et al (39) (142 mOsm kg j1 in intestinal fluids aspirated 25 cm from pylorus) and, as would be expected, lower than the value reported by Lindahl et al (14) for jejunal aspirates (271 mOsm kg j1 ).…”

“…These values are consistent with those reported earlier by Gisolfi et al (39) (mean of 29 mOsm kg j1 over an 85-min exercise period during which 1,850 mL water was concurrently administered), by Lindahl et al (14) (191 mOsm kg j1 , without prior water administration), and by Davenport (37) (171Y276 mOsm kg j1 , no indication of whether water was preadministered).…”

Sodium replacement and fluid shifts during prolonged exercise in humans

“…Gisol® et al (1995) have shown that up to 50 mEq of Na + ál ±1 has no aect on the absorption of water, Na + and glucose from a 6% carbohydrate solution. The same group has also found that a range of drink osmolalities from 0 to 400 mosmolákg ±1 does not aect the gastric emptying and absorption of¯uid ingested repeatedly during exercise (Gisol® et al 1998).…”

Review of the Effects of Glycerol-Containing Hyperhydration Solutions on Gastric Emptying and Intestinal Absorption in Humans and in Rats

“…Gisolfi, Summers, Lambert, and Xia (1998) showed that a hypertonic carbohydrate-electrolyte solution is absorbed as rapidly as water in the distal duodenum and proximal jejunum and that both solutions have a similar effect on plasma volume regulation during exercise. Over a 3-hr period, Freund et al (1995) demonstrated that GCHSs do not alter plasma volume compared with water, indirectly suggesting that they are absorbed as fast as water or a carbohydrateelectrolyte solution.…”