Carbohydrate gel ingestion during running in the heat on markers of gastrointestinal distress

The purpose of this study is to measure the effects of carbohydrate ingestion during exercise in the heat by measuring markers of gastrointestinal damage and inflammation. Methods: Active subjects (n = 7) completed two 60-min running trials in a heated environment (70% VO₂max, 30°C). At minute 20 of exercise, subjects consumed a carbohydrate gel (Cho) (27 g), or a non-carbohydrate placebo (nCho). Plasma endotoxin, I-FABP, TNF-α, IL-6, IL-1β, IL-10, and MCP-1 were measured pre-exercise, 20-min post-exercise, and again 2-h, and 4-h post-exercise. Results: Endotoxin increased 20-min post-exercise compared to pre in the Cho trial only (p = .03). I-FABP levels increased 20-min post-exercise in the Cho trial only compared to pre-exercise (p = .003). I-FABP levels were also increased in Cho trial 20-min post-exercise when compared to same time point in the nCho trial (p = .032). TNF-α increased 20-min post-exercise in the Cho trial only compared to pre (p = .03). Plasma IL-6 concentration increased 20-min post-exercise when compared to pre in both the Cho (p = .002) and nCho (p = .009), but remained elevated at the 2-h time point in the nCho trial (p = .03). I-FABP and several plasma cytokines (TNF-α, MCP-1, Il-6) returned to baseline sooner in the Cho trial. Conclusions: Ingestion of carbohydrate gel during exercise in the heat enhances markers of gastrointestinal wall damage.