By practicing your pre-race and race day nutrition many times prior to race day, you can improve absorption of nutrition, improve gut tolerance and learn what works (and doesn't work) to reduce the chance of GI distress and to improve performance.
Although GI distress is common among endurance athletes, race day performance-limiting upper- and lower-gastrointestinal (GI) issues are highly preventable.
Although causes are diverse and symptoms vary, there are ways to reduce your risk so that you can perform to your abilities and not spend unwanted time on the side of the road, in the bushes or in the portable toilet.