Introduction:
Gastrointestinal (GI) disturbances are common in endurance athletes due to physiological stress, reduced splanchnic blood flow, and dietary factors. Carbohydrate intake is essential for sustaining performance, but excessive consumption of simple sugars may impair gut barrier function and alter microbiota composition. Understanding how habitual carbohydrate quality affects gut barrier responses during exercise can guide dietary strategies to minimize gastrointestinal distress in athletes.
Methods:
Twenty-one male elite rowers performed a maximal 2000-meter rowing ergometer test. Dietary intake was recorded on the day before and the day of testing, and macronutrient composition was analyzed. Blood samples were collected pre-exercise, immediately post-exercise, and after a 1-hour recovery period. Serum concentrations of intestinal fatty acid-binding protein (I-FABP), lipopolysaccharide-binding protein (LBP), and claudin-3 (CLDN-3) were measured using ELISA assays.
Results:
I-FABP levels remained stable across all time points, suggesting no acute epithelial injury. CLDN-3 levels increased during recovery, indicating delayed tight junction remodeling (Cohen’s d =0,83; p = 0.0335). LBP concentrations decreased after exercise (Cohen’s d =0,88; p = 0.0,0042) and during recovery (Cohen’s d =1,51; p= 0.0002). LBP recovery values were positively correlated with glucose intake day before exercise test (r=0.56; p=0.008), and morning glucose levels (r=0.54; p=0.011), suggesting a link between the availability of simple carbohydrates and endotoxin-related immune responses. Habitual macronutrient intake had minimal influence on gut permeability markers, although glucose emerged as a key dietary factor affecting LBP dynamics.
Conclusion:
Short-term variations in carbohydrate intake showed minimal influence on resting gut permeability in elite athletes. Disturbances appeared mainly during recovery, marked by reduced LBP and delayed increases in claudin-3, indicating transient post-exercise epithelial stress. Modest links between glucose intake and endotoxin-related responses were preliminary but practically relevant findings. Overall, the gut barrier appears resilient, though recovery time remains a period of increased vulnerability. These findings provide applied insights for nutritionists designing carbohydrate strategies to preserve gastrointestinal health in endurance athletes.
Keywords: gut permeability, gut distress, athletes, I-FABP, claudin, athletes, rowers
Trial registration: NCT06403241 (registered retrospectively)
