The impact of (poly)phenol-rich sugarcane extract intervention on markers of gastrointestinal integrity and systemic inflammation in response to exertional-heat stress

Background Exertional-heat stress (EHS) perturbs gastrointestinal integrity, leading to systemic inflammation that may warrant medical attention. The study aimed to determine the effects of a (poly)phenol-rich sugarcane extract (PRSE) beverage and gel interventions on biomarkers of intestinal epithelial integrity and systemic immune responses to an EHS challenge.Method Using a double-blind placebo-controlled design, participants (n = 14) were randomly allocated to complete two EHS (i.e. 2 h running at 60% V˙O2max in 34.4 °C ambient temperature) trials, with at least one-week washout. Participants consumed 2 × 270 mL beverages daily for 14 days before EHS, and 1 × 270 mL beverage pre-EHS and a gel sachet every 20 min during EHS. Beverages and gels were either PRSE (beverage: 10% w/v, gel: 46% w/v) or carbohydrate-matched placebo. Whole blood samples were collected pre-EHS, immediately post-EHS and 30 min, 1 h, and 2 h post-EHS, and analyzed for plasma concentrations of cortisol, I-FABP, sCD14, and systemic inflammatory cytokines.Results Compared with placebo, the PRSE trial exhibited higher rectal temperature (p = 0.046) and physiological strain index (p = 0.010). No Trial × Time interaction was observed for I-FABP; however, pre-EHS plasma I-FABP concentration was lower in PRSE compared to placebo. Plasma IL-8 concentration increased over time (p < 0.001) that was attenuated by PRSE compared with placebo (p = 0.023). Exercise-associated gastrointestinal symptoms (Ex-GIS) incidence was high in both trials, while average symptom severity was lower with PRSE.Conclusion Two weeks of PRSE supplementation with a carbohydrate-containing beverage during EHS may provide modest advantages to intestinal epithelial integrity and systemic inflammatory, without further exacerbating Ex-GIS.