Gastrointestinal symptoms and nutritional strategies of endurance athletes

Lower gastrointestinal (GI) symptoms are common among endurance athletes and can negatively impact training and competition performance. These symptoms are similar to those characteristic of irritable bowel syndrome (IBS), a functional GI disorder affecting 10-20% of the U.S. population. A more recent strategy for IBS symptom management involves dietary restriction of fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP). Since carbohydrate consumption is typically promoted to improve endurance performance, it is possible that specific carbohydrate types are playing a role in symptom genesis; however, there has been little research in this area to date. The objectives of this study were to: 1) develop and validate a questionnaire to assess IBS diagnosis, fit to IBS diagnostic criteria, nutritional habits, GI symptoms, and symptom management strategies of endurance athletes, 2) characterize the IBS-related symptoms and treatment of endurance athletes, 3) examine the nutritional habits of endurance athletes from a FODMAP perspective, and 4) examine factors that influence low versus high FODMAP sports nutrition product use by endurance athletes. A 93-item Endurance Athlete Questionnaire (EAQ) was developed, with content and face validity provided by experts and endurance athletes, respectively. Test-retest reliability was established by target population athletes (participating in a marathon, ultramarathon, half distance triathlon, or full distance triathlon within that year). A nationwide implementation of the EAQ (n = 430) found that IBS is underdiagnosed, as in the general population. While 2.8% were medically diagnosed, an additional 7.0% met the most commonly used diagnostic criteria at the time (Rome III) and further athletes met previous, less restrictive IBS criteria (Manning). Despite various symptom management strategies, even more athletes than those with IBS experienced at least one symptom at a frequency of sometimes or more during exercise, indicating that IBS and IBS-like symptoms are ineffectively treated. A portion of the EAQ was also used to examine nutritional habits from a FODMAP perspective. Athletes commonly reported consuming potentially high FODMAP foods during pre-race dinners and breakfasts and more frequent consumption of various categories of sports nutrition products was related to increased symptom frequency. Analysis of the FODMAP content of the most popular beverages, gels, and commercial solid products using standardized methods revealed that many of these products have high FODMAP content, particularly when multiple servings are consumed, which is typical of use during endurance exercise. Habitual FODMAP intake in a sub-set of these athletes, evaluated using a previously validated, FODMAP-specific food frequency questionnaire, was high overall and athletes with various symptoms consumed higher levels of certain FODMAP groups. Popular gel and solid products with lower FODMAP content received higher overall liking scores in a sensory acceptance test by endurance athletes. Cluster analysis revealed different patterns in overall liking among groups, demonstrating that liking of low FODMAP products was somewhat individualized. The prices and online availability of low FODMAP products were comparable to the higher FODMAP products. While some low FODMAP gels were available at aid stations of popular endurance races, many races provided products of high or unknown FODMAP content. Overall, findings from this research support the potential application of low FODMAP nutritional interventions among endurance athletes by providing a scope of the symptomatic athletes who may benefit from such dietary manipulations as well as nutritional target areas for future low FODMAP research and practical application by athletes