Two weeks of repetitive gut‐challenge reduce exercise‐associated gastrointestinal symptoms and malabsorption

• Published in: Scandinavian journal of medicine & science in sports 2018-02, Vol.28 (2), p.630-640
• Main Authors: Miall, A., Khoo, A., Rauch, C., Snipe, R. M. J., Camões‐Costa, V. L., Gibson, P. R., Costa, R. J. S.
• Format: Article
• Language: English
• Subjects: Adult; breath hydrogen; Carbohydrate Metabolism; Carbohydrates; Dietary Carbohydrates - administration & dosage; Digestive system; discomfort; endurance; Exercise; Female; fructose; Fructose - administration & dosage; Gastrointestinal Diseases - prevention & control; Gastrointestinal Tract - physiopathology; glucose; Glucose - administration & dosage; gut training; Humans; Male; Oxygen Consumption; Running; Sports medicine; Sports training
• ISSN: 0905-7188; 1600-0838
• DOI: 10.1111/sms.12912

Debilitating gastrointestinal symptoms is a common feature of endurance running and may be exacerbated by and/or limit the ability to tolerate carbohydrate intake during exercise. The study aimed to determine whether two weeks of repetitive gut‐challenge during running can reduce exercise‐associated gastrointestinal symptoms and carbohydrate malabsorption. Endurance runners (n=18) performed an initial gut‐challenge trial (GC1) comprising 2‐hour running exercise at 60% VO2max (steady state) while consuming a formulated gel‐disk containing 30 g carbohydrates (2:1 glucose‐fructose, 10% w/v) every 20 minutes, followed by a 1‐hour running effort bout. Gastrointestinal symptoms, feeding tolerance, and breath hydrogen (H2) were determined along the gut‐challenge trial. After GC1, participants were randomly assigned to a blinded carbohydrate (CHO, 90 gCHO hour−1) or placebo (PLA, 0 gCHO hour−1) gut‐training group. This comprised of consuming the group‐specific feeding intervention during 1‐hour running exercise at 60% VO2max equivalent, daily over a period of two weeks. Participants then repeated the gut‐challenge trial (GC2). In GC2, a reduced gut discomfort (P=.012), total (P=.009), upper‐ (P=.015), and lower‐gastrointestinal (P=.008) symptoms, and nausea (P=.05) were observed on CHO, but not PLA. Feeding tolerance did not differ between GC1 and GC2 on CHO and PLA. H2 peak was attenuated in GC2 (6±3 ppm) compared to GC1 (13±6 ppm) on CHO (P=.004), but not on PLA (GC1 11±7 ppm, and GC2 10±10 ppm). The effort bout distance was greater in GC2 (12.3±1.3 km) compared with GC1 (11.7±1.5 km) on CHO (P=.035) only. Two weeks of repetitive gut‐challenge improve gastrointestinal symptoms and reduce carbohydrate malabsorption during endurance running, which may have performance implications.