A 16% Carbohydrate-hydrogel Beverage Reduces Gastrointestinal Permeability And Enterocyte Damage After Cycling In Hot-humid Conditions

Abstract

BACKGROUND: Carbohydrate ingestion during exertional heat stress can reduce enterocyte damage and preserve gastrointestinal permeability. Athletes have begun to use drinks which encapsulate carbohydrate within a pectin-alginate hydrogel, yet little evidence exists to support their preferential use versus traditional carbohydrate-gels and/or beverages with multiple transportable carbohydrates. PURPOSE: To compare the effects of consuming a 16% carbohydrate-hydrogel drink to a nutrient matched maltodextrin-fructose (MF) drink on enterocyte damage and gastrointestinal permeability after cycling in hot and humid conditions. METHODS: Fourteen endurance trained cyclists (7 men, age 27 ± 8 yr, 176 ± 10 cm, 74 ± 11 kg, VO2max: 55.2 ± 9.5 ml.kg-1.min-1) cycled (45% VO2max) for 90 minutes before completing a 15-minute time trial in hot humid conditions (32°C, 70%) on 3 occasions separated by 7 days. During trials participants consumed either water (W), a traditional MF drink, or an encapsulated carbohydrate hydrogel drink (HYDRO) in a randomised order. Each CHO drink provided 90 g CHO.hr (16% w/v). Twenty minutes into exercise a 50 mL drink containing lactulose (L; 5 g) and rhamnose (R; 2 g) was provided and intestinal permeability determined by the percent ratio of lactulose to rhamnose recovered in post exercise urine samples. Venous blood samples were obtained before and 5 minutes after the time trial for assessment of intestinal fatty acid binding protein (IFABP), and data analysed using mixed linear models with fixed effects for condition (W/MF/HYDRO) and time (before and after exercise). RESULTS: L:R was greatest in W, and lower in both HYDRO [by 0.019 (95% CI: 0.010 to 0.027), p = 0.0003], and GF [by 0.014 (95% CI: 0.006 to 0.022), p = 0.0018]. No differences in L:R were found between the H and GF conditions (p = 0.083). Post-exercise IFABP concentrations were greater in W compared to HYDRO [by 349 pg.mL-1 (95% CI: 137 to 561 pg.mL-1), p = 0.007] and GF [by 427 pg.mL-1 (95% CI: 152 to 701 pg.mL-1), p = 0.018]. There was no difference in post exercise IFABP concentrations between H and GF (p = 0.90). CONCLUSION: Both CHO drinks preserved intestinal permeability and reduced the appearance of circulating IFABP compared to W. HYDRO offered no additional benefit beyond those achieved with a traditional MF drink.