The Summary
In a randomized, double-blind crossover trial, 12 active men consumed targeted resistant starch to elevate colonic short-chain fatty acids (SCFAs) or a control starch for seven days. After 90 minutes of cycling followed by a five-kilometer time trial, researchers assessed metabolic markers and intestinal integrity. The SCFA supplement successfully reduced exercise-induced gut barrier damage and permeability. However, contrary to earlier rodent studies, increasing SCFAs did not alter glucose turnover, spare muscle glycogen, or improve running performance in humans.
Why this is interesting
Past animal studies sparked excitement by suggesting that gut-derived SCFAs could serve as an alternative fuel source to spare glycogen and boost endurance. This human trial provides an essential reality check: while SCFAs effectively defend the intestinal lining against exercise-induced stress and leakiness, they do not translate into faster race times or greater stamina. For athletes, prebiotic strategies remain valuable for preventing exercise-related gut distress, but they should not be relied upon as a direct performance-enhancing fuel.