Trainers Say This 'Healthy' Nutrient Could Ruin Your Race-Day Comfort

If you've ever experienced runner's gut, you know just how miserable a feeling it is. Sometimes there’s nothing you can do to prevent the phenomena, triggered by reduced blood flow to the gut, intense exercise, and environmental factors. But if you want to take every measure possible to avoid compromising your race day PR with lengthy porta-potty stops, limit fiber-rich foods the day before your race.

"Most health advice tells you for better digestion, eat as much fiber as possible—but we...