The Effects of Prebiotic Supplementation on Markers of Exercise-Induced Gastrointestinal Syndrome in Response to Exertional Heat Stress

Exercise perturbs various aspects of gastrointestinal integrity and function, which may lead to performance impeding gastrointestinal symptoms (GIS) and/or precipitate clinical issues warranting medical management. This study aimed to determine the impact of prebiotic supplementation on gastrointestinal integrity and functional status in response to exertional heat stress (EHS). Sixteen endurance athletes completed two trials of 3-hr running at 60% (center dot)VO2max in 30 degrees C at baseline (T1) and following an 8-week supplementation period (T2), with 16 g/day prebiotic (PREBIOTIC) or matched placebo (PLACEBO). Blood samples were collected pre-EHS and post-EHS and in recovery for determination of stress response (cortisol), intestinal epithelial injury (intestinal fatty acid binding protein), bacterial endotoxemia (sCD14), and systemic inflammation (C-reactive protein). GIS and feeding tolerance variables were assessed throughout the EHS. Orocecal transit time was determined via a lactulose challenge given at 2.5 hr into EHS. Plasma cortisol (combined mean: +252 ng/ml), intestinal fatty acid binding protein (+800 pg/ml), and sCD14 (+487 ng/ml) concentrations increased in response to EHS in T1 (p <= .05), but not for C-reactive protein (+0.8 mu g/ml; p > .05), in both PREBIOTIC and PLACEBO. PREBIOTIC supplementation resulted in a blunted intestinal fatty acid binding protein response on T2 (+316 pg/ml) compared with an increase (+1,001 ng/ml) in PLACEBO (p=.005). Lower sCD14 was observed at T2 (2,799 ng/ml) versus T1 (3,246 ng/ml) in PREBIOTIC only (p=.039). No intervention effects were observed for C-reactive protein. No difference within or between PREBIOTIC and PLACEBO at T1 and T2 was observed for orocecal transit time, GIS, and feeding tolerance. In conclusion, 8 weeks of prebiotic supplementation modestly attenuates EHS associated perturbations to intestinal integrity, but does not further impair gastrointestinal transit and/or exacerbate EHS associated GIS or feeding tolerance.