Gastrointestinal function during exercise: comparison of water, sports drink, and sports drink with caffeine

Caffeine is suspected to affect gastrointestinal function. We therefore inv estigated whether supplementation of a carbohydrate-electrolyte solution (C ES) sports drink with 150 mg/l caffeine leads to alterations in gastrointes tinal variables compared with a normal CES and water using a standardized r est-exercise-rest protocol. Ten well-trained subjects underwent a rest-cycl ing-rest protocol three times. Esophageal motility, gastroesophageal reflux , and intragastric pH were measured by use of a transnasal catheter. Orocec al transit time was measured using breath-H-2 measurements. A sugar absorpt ion test was applied to determine intestinal permeability and glucose absor ption. Gastric emptying was measured via the C-13-acetate breath test. In t he postexercise episode, midesophageal pressure was significantly lower in the CES + caffeine trial compared with the water trial (P = 0.017). There w ere no significant differences between the three drinks for gastric pH and reflux during the preexercise, the cycling, and the postexercise episode, r espectively. Gastric emptying, orocecal transit time, and intestinal permea bility showed no significant differences between the three trials. However, glucose absorption was significantly increased in the CES + caffeine trial compared with the CES trial (P = 0.017). No significant differences in gas troesophageal reflux, gastric pH, or gastrointestinal transit could be obse rved between the CES, the CES + caffeine, and the water trials. However, in testinal glucose uptake was increased in the CES + caffeine trial.