Applying a Low-FODMAP dietary intervention to a female ultraendurance runner with irritable bowel syndrome during a multistage ultramarathon

Malabsorption of fermentable oligo-, di-, mono-saccharides and polyols (FODMAPs) in response to prolonged exercise may increase incidence of upper and lower gastrointestinal symptoms (GIS), which are known to impair exercise performance. This case study aimed to explore the impact of a low-FODMAP diet on exercise-associated GIS in a female ultraendurance runner diagnosed with irritable bowel syndrome, competing in a 6-day 186.7-km mountainous multistage ultramarathon (MSUM). Irritable bowel syndrome symptom severity score at diagnosis was 410 and following a low-FODMAP diet (3.9 g FODMAPs/ day) it reduced to 70. The diet was applied 6 days before (i.e., lead-in diet), and maintained during (5.1 g FODMAPs/day) the MSUM. Nutrition intake was analyzed through dietary analysis software. A validated 100-mm visual analog scale quantified GIS incidence and severity. GIS were modest during the MSUM (overall mean ± SD: bloating 27 ± 5 mm and flatulence 23 ± 8 mm), except severe nausea (67 ± 14 mm) experienced throughout. Total daily energy (11.7 ± 1.6 MJ/day) intake did not meet estimated energy requirements (range: 13.9–17.9 MJ/day). Total daily protein [1.4 ± 0.3 g·kg body weight (BW) ⁻¹ ·day ⁻¹ ], carbohydrate (9.1 ± 1.3 g·kg BW ⁻¹ ·day ⁻¹ ), fat (1.1 ± 0.2 g·kg BW ⁻¹ ·day ⁻¹ ), and water (78.7 ± 6.4 ml·kg BW ⁻¹ ·day ⁻¹ ) intakes satisfied current consensus guidelines, except for carbohydrates. Carbohydrate intake during running failed to meet recommendations (43 ± 9 g/hr). The runner successfully implemented a low-FODMAP diet and completed the MSUM with minimal GIS. However, suboptimal energy and carbohydrate intake occurred, potentially exacerbated by nausea associated with running at altitude.