The Effect of a Repetitive Feeding Challenge With Carbohydrate Versus Fat on Markers of Gastrointestinal Integrity and Systemic Outcomes in Response to Endurance Exercise.

Athletes report consuming nutritionally dense foods before and during exercise to manage gastrointestinal symptoms (GIS). The study investigated whether fat, compared with carbohydrate (CHO), as a gut-training supplement, compromises gastrointestinal integrity and triggers systemic inflammation in response to endurance exercise. Thirty-six endurance athletes (seven females and 29 males) completed a preintervention gut-challenge trial (T1), involving a 2-hr run (60%V˙O2max) with CHO gel intake every 20 min (87 g/hr), followed by a 1-hr self-paced distance test. Participants were randomized to a fat (FFC; 20 g nut butter) or CHO supplement (CFC; 47 g CHO gel) for a feeding-challenge protocol (1 hr exercise with supplement for 7 days), followed by a gut-challenge retrial (T2). During T1 and T2, blood samples were collected before and after exercise to measure intestinal fatty-acid binding protein (I-FABP), soluble CD14 (sCD14), and C-reactive protein (CRP). Pre- to postexercise peak responses were similar within and between groups for plasma I-FABP (FFC: 254 ± 495 vs. 349 ± 622 pg/ml, p = .911; CFC: 344 ± 336 vs. 421 ± 362 pg/ml, p = .501; between groups T1: p = .404; T2: p = .440) and sCD14 (FFC: 0.346 ± 0.703 vs. 0.175 ± 0.603 μg/ml, p = .509; CFC: 0.336 ± 0.522 vs. 0.546 ± 0.777 μg/ml, p = .587; between groups T1: p = .888; T2: p = .149). CRP was significantly reduced in CFC (0.327 ± 0.449 vs. 0.062 ± 0.231 μg/ml, p = .030) but not in FFC (p = .351). Total-GIS severity during exercise or recovery were not correlated with I-FABP, sCD14, and CRP. The repetitive feeding-challenge with fat, compared with CHO, did not increase markers of gastrointestinal injury, bacterial endotoxin translocation, and systemic inflammation in response to endurance exercise.