Effect of Carbohydrate Gels on Gastrointestinal Tolerance During a 16-km Run

• Published in: International journal of sport nutrition and exercise metabolism 2009-10, Vol.19 (5), p.485-503
• Main Authors: Pfeiffer, Beate, Cotterill, Alexandra, Grathwohl, Dominik, Stellingwerff, Trent, Jeukendrup, Asker E
• Format: Article
• Language: English
• Subjects: Administration, Oral; Adult; carbohydrate gels; carbohydrate intake; Cross-Over Studies; Dietary Carbohydrates - administration & dosage; Dietary Carbohydrates - adverse effects; Drinking; Female; fructose; Fructose - administration & dosage; Fructose - adverse effects; Gastrointestinal Diseases - etiology; gastrointestinal system; gastrointestinal tolerance; Gastrointestinal Tract - drug effects; Gastrointestinal Tract - metabolism; Gastrointestinal Tract - physiology; Gels; glucose; Glucose - administration & dosage; Glucose - adverse effects; high carbohydrate diet; Humans; Male; men; nutrient uptake; Oxidation-Reduction; Oxygen Consumption; Physical Endurance - drug effects; Physical Endurance - physiology; questionnaires; running; Running - physiology; Task Performance and Analysis; women
• ISSN: 1526-484X; 1543-2742
• DOI: 10.1123/ijsnem.19.5.485

Two studies were conducted to investigate gastrointestinal (GI) tolerance of high carbohydrate (CHO) intakes during intense running. The first study investigated tolerance of a CHO gel delivering glucose plus fructose (GLU+FRC) at different rates. The second study investigated tolerance of high intakes of glucose (GLU) vs. GLU+FRC gel. Both studies used a randomized, 2-treatment, 2-period crossover design: Endurance-trained men and women (Study 1: 26 men, 8 women; 37 ± 11 yr; 73 ± 9 kg; 1.76 ± 0.07 m. Study 2: 34 men, 14 women; 35 ± 10 yr; 70 ± 9 kg; 1.75 ± 0.09 m) completed two 16-km outdoor-runs. In Study 1 gels were administered to provide 1.0 or 1.4 g CHO/min with ad libitum water intake every 3.2 km. In Study 2 GLU or GLU+FRC gels were given in a double-blind manner to provide 1.4 g CHO/ min. In both studies a postexercise questionnaire assessed 17 symptoms on a 10-point scale (from 0 to 9). For all treatments, GI complaints were mainly scored at the low end of the scale. In Study 1 mean scores ranged from 0.00 ± 0.00 to 1.12 ± 1.90, and in Study 2, from 0.00 ± 0.0 to 1.27 ± 1.78. GI symptoms were grouped into upper abdominal, lower abdominal, and systemic problems. There were no significant treatment differences in these categories in either study. In conclusion, despite high CHO-gel intake, and regardless of the blend (GLU vs. GLU+FRC), average scores for GI symptoms were at the low end of the scale, indicating predominantly good tolerance during a 16-km run. Nevertheless, some runners (approximately 10–20%) experienced serious problems, and individualized feeding strategies might be required.