Nutrient and Fluid Intake and Gastrointestinal Problems during Prolonged Endurance Events

Abstract

There is little information about the actual nutrition and fluid intake habits, and gastrointestinal (GI) symptoms of athletes during endurance events. PURPOSE: To characterize nutrient intakes during endurance competitions and investigate links to GI symptoms, performance and race characteristics (type, length, weather). Method: 221 endurance athletes (male and female) were recruited from two Ironman triathlons (IM Hawaii and IM GER), a half-Ironman (IM70.3), a MARATHON, a 100/150 km CYCLE race. Professional cyclists (PRO) were investigated during stage-racing. A standardized post-race questionnaire quantified nutrient intake and assessed 12 GI symptoms on a scale from 0 (no problem) to 9 (worst it has ever been). RESULTS: Mean CHO intake rates were not significantly different between IM Hawaii, IM GER and IM70.3 (62±26, 71±25 g/h and 65±25 g/h, respectively), but these rates were significantly greater than CYCLE (53±22 g/min, p=0.041) and MARATHON (35±26 g/min; p<0.01). Prevalence of serious GI symptoms were highest during the IM races (∼31%; p<0.01) compared with IM70.3 (14%), CYCLE (4%), MARATHON (4%) and PRO (7%), and correlated to a previous history of GI problems (p<0.01) and heat index (p<0.01). Training experience was linked to lower prevalence of GI distress (r=-0.373; p=0.008). Total CHO intake rates were positively correlated with nausea and flatulence, but negatively correlated with finishing time during both IM (r=-0.55 and r=-0.48; p<0.001), with a ∼20% higher (p=0.06) CHO intake rate in PRO compared to amateurs. CONCLUSION: The present study demonstrated that CHO intake rates vary greatly between events and individual athletes (6-136 g/h). High CHO intake rates were not associated with higher average scores for upper or lower GI symptoms, but appeared to be a risk factor for nausea and flatulence. However, high CHO intake rates were significantly correlated with faster finishing times. Reported GI symptoms during events were linked to a reported history of GI distress. Altogether the findings suggest a need for more individualized nutritional advice that optimizes CHO and fluid delivery to enhance performance, whilst minimizing GI discomfort. This study was supported by a Research Grant from Nestec Ltd., Nestlé Nutrition, Vevey, Switzerland.