Food and fluid intake and disturbances in gastrointestinal and mental function during an ultramarathon

The purpose of this study was to document eating strategies employed by runners during a 160-km race, and to identify eating patterns that predispose the runner to disturbed mental or gastrointestinal functioning. We monitored intake in 19 volunteers during the 12 hours pre-race. Intake was determined by interview with runners approximately every 12 km throughout the race. The mean finish time was 24.3 hours, with 4 runners not completing the race. Body mass decreased during the race, 75.9 +/- 2.3 kg to 74.4 +/- 2.2 kg (p <.001). Runners ingested 2643 kcals during the 12 hours prerace (68% carbohydrate) and 3.8 L of fluid. During the race 6047 kcal, 18 L of fluid, and 12 g of sodium were consumed. Gastrointestinal distress (GI) was experienced by half of the participants, but was unrelated to food or fluid intake. Upper GI symptoms were more prevalent than lower and occurred mainly after 88 km. Runners with GI distress tended to complete fewer training miles (p =.10) and to do shorter training runs (p =.08). Half of the volunteers reported mental status changes (MSC), such as confusion or dizziness. Runners with MSC had greater intake of total calories, carbohydrate, and fluid (p <.05) than runners without MSC. They also completed shorter training runs (p =.03). Caloric and moisture intake for all runners far exceeded intakes described previously. Although intake did not match energy expenditure, it may represent the upper limit for absorption during exercise, and very high food and/or fluid intake appears to lead to perturbed mental status.