Author(s): JOHNSON, K., ROWLAND, S., MAHON, E., SPRUNG, T., LANGAN-EVANS, C., BASS, L., Institution: LIVERPOOL JOHN MOORES UNIVERISTY, Country: UNITED KINGDOM, Abstract-ID: 1033

INTRODUCTION:
Exercise-associated gastrointestinal (GI) symptoms are reported during prolonged endurance exercise, with prevalence reported as high as 90% in some athletic populations, although severity varies between individuals and conditions. Female athletes remain underrepresented in GI research despite known sex-related differences in gastrointestinal physiology. Postbiotics may influence gut function; however, evidence in exercising females is limited. This study evaluated GI symptom responses and circulating markers of gut integrity during prolonged running before and after a postbiotic supplementation period.
METHODS:
Twenty four naturally menstruating, recreationally endurance trained females (age 34 ± 7 years; height 164 ± 6.2 cm; body mass 63.0 ± 5.7 kg; BMI 23.4 ± 2.1 kg m⁻²; VO₂max 51.0 ± 6.1 mL·kg⁻¹·min⁻¹) completed a double blind randomised placebo controlled crossover design. Gastrointestinal symptoms were the primary outcome used to determine sample size. Participants consumed a postbiotic yeast preparation or maltodextrin placebo daily for one menstrual cycle (29 ± 3 days). Trials were performed in the early follicular phase. Participants completed a continuous 120 min treadmill run at 95% first lactate threshold (LT1) in 34°C, 40% relative humidity. Symptom severity (median, IQR) was analysed using Wilcoxon signed-rank tests. Circulating CD14 and intestinal fatty acid binding protein were measured pre and post exercise.
RESULTS:
The prevalence of several gastrointestinal symptoms was reduced following the postbiotic period, including nausea, side stitch, urge to burp, urge to defecate and stomach cramps, whereas prevalence showed no consistent change in placebo. Wilcoxon signed-rank analysis of median (IQR) symptom scores demonstrated baseline to 120 min increases in several symptoms prior to supplementation (all p<0.05) that were not observed following the postbiotic period, whereas increases persisted in placebo. Categorical severity classifications did not differ between conditions (p>0.05). Circulatory markers increased with exercise (p<0.05) with no group by time interaction.
CONCLUSION:
Following the postbiotic supplementation period, exercise-induced increases in several upper and lower gastrointestinal symptoms were no longer observed, whereas increases persisted in placebo. No differences were identified in categorical severity classifications or circulating markers of gut integrity. The absence of concurrent changes in circulating markers of gut permeability or endotoxin translocation indicates that alterations in symptom responses may occur independently of detectable systemic inflammatory or barrier disruption. Collectively, these data highlight the complexity of gastrointestinal responses to prolonged exercise and support further investigation into gut-targeted strategies in female endurance populations.