Martinez et al. 2023, gut-training and feeding-challenge in endurance exercise systematic review

This systematic review screened 304 publications and included eight studies examining the effect of gut-training or feeding-challenge interventions on gastrointestinal status during endurance exercise. Two-week high-carbohydrate protocols reduced breath-hydrogen peak responses (a marker of carbohydrate malabsorption) by 45–54% and gut discomfort by roughly 47% (with the 2-week high-carbohydrate protocol) and 26% (with a repeated fluid-ingestion protocol); results across studies were directionally consistent but methodologically heterogeneous. The authors concluded that gut-training may provide advantages in reducing malabsorption and exercise-associated gastrointestinal symptoms, while calling for standardised assessment tools. Moderate evidence.