Background: Endurance runners frequently experience exercise-induced gastrointestinal (GI) symptoms, negatively impacting their performance. Food choices pre-exercise have a significant impact on the gut's tolerance to running, yet little information is available as to which foods runners restrict prior to exercise. Methods: A questionnaire designed to assess dietary restrictions pre-racing and gastrointestinal symptoms was administered to 388 runners. Fisher's exact tests determined differences in gender, age, performance level, and distance with follow-up multivariable logistic regression modeling. Results: Runners regularly avoided meat (32%), milk products (31%), fish/seafood (28%), poultry (24%), and highfiber foods (23%). Caffeinated beverages were commonly avoided in events 10 km or less (p < .001); whereas in females, increased running distance was a predictor of avoiding high-fiber foods (OR = 6.7; 95% CI = 1.6-28.5). Rates of food avoidance were elevated in younger and more competitive runners. Common GI symptoms included stomach pain/cramps (42%), intestinal pain/discomfort (23%), side ache/stitch (22%), urge to defecate (22%), and bloating (20%). The prevalence of GI symptoms was higher in younger athletes, especially females, which may explain their propensity to avoid foods. Lower recreational athletes were the least likely to report GI symptoms. Diarrhea incidence increased with running distance. Conclusions: Identification of voluntary food restrictions in the pre-running meal highlights trends that can direct further research.

Background Exercise induced gastrointestinal (GI) symptoms can plague athletes, especially runners. Sport nutrition recommendations are nutrient rather than foods focused and do not adequately address strategies to reduce GI symptoms. The objective was to develop a valid and reliable questionnaire to evaluate pre-training and pre-racing voluntary food restrictions/choices, reasons for avoiding foods, and gastrointestinal symptoms in endurance runners. Methods Validity testing occurred through four Registered Dietitians, three of whom possess Master’s degrees, and a dietetic trainee who provided initial feedback. Additionally, one Registered Dietitian is a Board Certified Specialist in Sports Dietetics (CSSD), and another has an International Olympic Committee Diploma in Sports Nutrition. The second version was sent out to nine different experts who rated each question using a Likert scale and provided additional comments. For reliability testing, the questionnaire was administered to 39 participants in a test re-test format. Kappa statistics and the prevalence-adjusted bias-adjusted kappa (PABAK) were used to assess the reliability. Results All questions had an average Likert scale rating of 4/5 or greater. All test re-test results falling under basic information exhibited substantial agreement (kappa ≥0.61). All medical questions including food allergies and intolerances had moderate (kappa ≥0.41) or higher agreement. Responses were less consistent for food avoidances while training (5/28 outcomes) versus racing (0/28 outcomes) with a kappa below 0.41. All reasons for avoiding foods were deemed reliable. Regarding symptoms, side stitch while training and gas while racing were the only flagged categories. Conclusions Overall, the questionnaire is a valid and reliable tool to evaluate voluntary dietary restrictions among endurance runners. Future studies can use the questionnaire to assess dietary strategies runners employ to reduce GI distress and optimize performance. Electronic supplementary material The online version of this article (10.1186/s12970-019-0278-7) contains supplementary material, which is available to authorized users.

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