Dietary Intake and Gastrointestinal Integrity in Runners Undertaking High-Intensity Exercise in the Heat

Abstract

Gastrointestinal disturbances are one of the most common issues for endurance athletes during training and competition in the heat. The relationship between typical dietary intake or nutritional interventions and perturbations in or maintenance of gut integrity is unclear. Twelve well-trained male endurance athletes (peak oxygen consumption = 61.4 ± 7.0 ml·kg−1·min−1) completed two trials in a randomized order in 35 °C (heat) and 21 °C (thermoneutral) conditions and kept a detailed nutritional diary for eight consecutive days between the two trials. The treadmill running trials consisted of 15 min at 60% peak oxygen consumption, 15 min at 75% peak oxygen consumption, followed by 8 × 1-min high-intensity efforts. Venous blood samples were taken at the baseline, at the end of each of the three exercise stages, and 1 hr postexercise to measure gut integrity and the permeability biomarker concentration for intestinal fatty-acid-binding protein, lipopolysaccharide, and lipopolysaccharide-binding protein. The runners self-reported gut symptoms 1 hr postexercise and 3 days postexercise. The heat condition induced large (45–370%) increases in intestinal fatty-acid-binding protein, lipopolysaccharide-binding protein, and lipopolysaccharide concentrations compared with the baseline, but induced mild gastrointestinal symptoms. Carbohydrate and polyunsaturated fat intake 24 hr preexercise were associated with less lipopolysaccharide translocation. Protein, carbohydrate, total fat, and polyunsaturated fat intake (8 days) were positively associated with the percentage increase of intestinal fatty-acid-binding protein in both conditions (range of correlations, 95% confidence interval = .62–.93 [.02, .98]). Typical nutrition intake partly explained increases in biomarkers and the attenuation of symptoms induced by moderate- and high-intensity exercise under both heat and thermoneutral conditions.

Gut Leakage and Cardiac Biomarkers after Prolonged Strenuous Exercise

“…sCD14 increased significantly from baseline levels to after and the day after the race, in line with previous studies (21,22). LBP also increased significantly, in accordance with several studies on short-term strenuous exercise (23,24). The increase in sCD14 and LBP might suggest activation of an LPS-driven inflammatory pathway.…”

Anthocyanin-Rich Blackcurrant Extract Preserves Gastrointestinal Barrier Permeability and Reduces Enterocyte Damage but Has No Effect on Microbial Translocation and Inflammation After Exertional Heat Stress

“…However, recent recommendations for maximizing performance in endurance athletes do call for some exercise sessions to be performed under fasted conditions, the so-called Sleep-Low model (Riis et al, 2019). Moreover, a fasted exercise state was required to ensure accuracy and validity of the dual sugar absorption test, and to minimise the effects of dietary intake on I-FABP release (Etxebarria et al, 2021). It is plausible that the observed effects to small intestinal permeability and plasma I-FABP may be lost when exercise is performed following adequate dietary carbohydrate/protein intake prior to and during exercise (Snipe et al, 2017b).…”

“…For 24 h before each visit, participants refrained from strenuous exercise and alcohol. Macronutrient intake has been shown to alter GI barrier permeability (Etxebarria et al, 2021) and post exercise I-FABP responses (Snipe et al, 2017a), therefore participants attended the laboratory after an ~10 h overnight fast. On the morning of each experimental visit participants were instructed to drink 500 mL of water and take their final 2 capsules 2 hours before attending.…”

Best Practices for Probiotic Research in Athletic and Physically Active Populations: Guidance for Future Randomized Controlled Trials

“…Other investigators have examined the frequency of symptoms subjectively scored as “moderate” severity or worse [e.g., ( 45 , 67 , 75 )]. Readers are directed to the following resources for examples of validated and commonly used tools/questionnaires ( 70 , 73 , 74 , 76 ). Implementation of these may help reduce much of the heterogeneity in the current body of evidence.…”