Nutritional Management of IBS-complicated Exercise-Induced Gastrointestinal Syndrome




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Background: The mechanism behind exercise-induced gastrointestinal syndrome (Ex-GIS) causing abdominal pain related to exercise is proposed to be due to altered gastrointestinal blood flow and neuroendocrine changes. Ex-GIS is found in up to 70% of athletes performing intense endurance exercise and can imitate the symptoms of Irritable Bowel Syndrome (IBS). However, the availability of research addressing the coexistence of IBS and Ex-GIS in athletes is limited. This is complicated by the underreported and underdiagnosed nature of IBS. Case Information: A 24 y/o male recreational triathlete presented with a chief complaint of chronic gastrointestinal distress both during and after endurance exercise. He described his abdominal pain as crampy with an excessive amount of bloating. High intensity long-distance running exacerbated his pain, but he obtained minor relief using OTC loperamide HCl 2mg with simethicone 125mg PRN and also by ceasing physical activity. Past medical history included painless hematochezia and Irritable Bowel Syndrome-Mixed (IBS-M). He endorsed consuming a high FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) diet of poorly digestible carbohydrates and lactose-intolerance that was poorly controlled with the inconsistent use of lactase enzyme supplements. On physical exam, the patient appeared well and was in no acute distress. The only physical exam findings were hyperactive bowel sounds on abdominal auscultation. The differential diagnoses included IBS, Ex-GIS, and Ex-GIS complicated by comorbid IBS. The patient received a colonoscopy in 2021 to rule out lower GI pathology. The colonoscopy results indicated internal hemorrhoids, which could help explain the painless hematochezia. However, the biopsy results and gross examination were otherwise normal. As a result, the patient received a diagnosis of IBS-mixed, by exclusion, and the patient was prescribed dicyclomine 10mg twice daily, but has been non-compliant due to unfavorable side effects. Searching for a non-medication based treatment, the patient turned towards dietary and behavioral modifications to seek relief. Preliminary research suggests that endurance athletes routinely eat up to 43g of FODMAPs/day, nearly twice the recommended amount, and that athletes suffering from Ex-GIS should consume a low FODMAP diet of 5-18g/day. Additionally, athletes who have Ex-GIS complicated by IBS should further reduce their FODMAP intake to under 3g/day. Conclusions: This case represents a unique presentation of exercise-induced gastrointestinal syndrome, further complicated by IBS symptoms. By consuming a low FODMAP diet, patients may be able to obtain significant symptom relief from IBS-complicated exercise-induced gastrointestinal syndrome. However, more research needs to be completed to address the dichotomy of high FODMAP foods being beneficial for athletic performance, while exacerbating symptoms in patients suffering from IBS-complicated Ex-GIS.