Nutritional intake and gastrointestinal problems during competitive endurance events

Med Sci Sports Exerc. 2012 Feb;44(2):344-51. doi: 10.1249/MSS.0b013e31822dc809.


There is little information about the actual nutrition and fluid intake habits and gastrointestinal (GI) symptoms of athletes during endurance events.

Purpose: This study aimed to quantify and characterize energy, nutrient, and fluid intakes during endurance competitions and investigate associations with GI symptoms.

Method: A total of 221 endurance athletes (male and female) were recruited from two Ironman triathlons (IM Hawaii and IM GER), a half-Ironman (IM 70.3), a MARATHON, a 100/150-km CYCLE race. Professional cyclists (PRO) were investigated during stage racing. A standardized postrace questionnaire quantified nutrient intake and assessed 12 GI symptoms on a scale from 0 (no problem) to 9 (worst it has ever been) in each competition.

Results: Mean CHO intake rates were not significantly different between IM Hawaii, IM GER, and IM 70.3 (62 ± 26, 71 ± 25, and 65 ± 25 g·h(-1), respectively), but lower mean CHO intake rates were reported during CYCLE (53 ± 22 g·h(-1), P = 0.044) and MARATHON (35 ± 26 g·h(-1), P < 0.01). Prevalence of serious GI symptoms was highest during the IM races (∼31%, P = 0.001) compared with IM 70.3 (14%), CYCLE (4%), MARATHON (4%), and PRO (7%) and correlated to a history of GI problems. In all data sets, scores for upper and lower GI symptoms correlated with a reported history of GI distress (r = 0.37 and r = 0.51, respectively, P < 0.001). Total CHO intake rates were positively correlated with nausea and flatulence but were negatively correlated with finishing time during both IM (r = -0.55 and r = -0.48, P < 0.001).

Conclusions: The present study demonstrates that CHO intake rates vary greatly between events and individual athletes (6-136 g·h(-1)). High CHO intake during exercise was related not only to increased scores for nausea and flatulence but also to better performance during IM races.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Athletes
  • Athletic Performance / physiology
  • Bicycling / physiology
  • Dietary Carbohydrates / adverse effects*
  • Drinking / physiology*
  • Eating / physiology*
  • Female
  • Flatulence / physiopathology
  • Humans
  • Male
  • Middle Aged
  • Nausea / physiopathology
  • Physical Endurance / physiology*
  • Running / physiology
  • Swimming / physiology


  • Dietary Carbohydrates