Plain language summary
Practising endurance exercise in the heat is a common practice among endurance athletes. Endurance exercise combined with heat exposure is known to affect the gastrointestinal system. As per statistics, more than 60% of the people who practice endurance exercise in the heat experience intestinal permeability and endotoxemia. Randomised, counterbalanced cross-over trials were conducted on 12 well-trained male runners to determine whether a well-balanced diet would ameliorate gastrointestinal disturbances induced by high-intensity endurance exercise in hot (35 degrees) or thermoneutral conditions (21 degrees). High carbohydrate and polyunsaturated fat diet twenty-four hours before endurance exercise in the heat may reduce lipopolysaccharide translocation into the circulatory system. Consuming a high-carbohydrate, high-protein diet 24 hours before endurance exercise in a thermoneutral condition reduces gastrointestinal symptoms. Despite this, high-intensity endurance exercise in the heat produced modest gastrointestinal symptoms compared to thermoneutral conditions. Consumption of carbohydrate, protein, total fat and polyunsaturated fat for eight days was positively correlated with intestinal fatty-acid-binding protein response after endurance exercise in the heat and thermoneutral conditions. This study can help healthcare professionals better understand the relationship between dietary factors and gastrointestinal symptoms during endurance exercise in different temperature conditions.
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.
Methodological quality
Jadad score
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1
Allocation concealment
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No
