Carbohydrate Hydrogel Beverage Does Not Improve Gastrointestinal Symptoms Or Running Performance Versus Conventional Carbohydrate Beverages

PURPOSE: The utilization of ‘hydrogel’ technology allows carbohydrate beverages to form a gel in the acidic environment of the stomach, potentially enhancing gastric emptying. However, the effects of these beverages on gastrointestinal (GI) symptoms and exercise performance have not been sufficiently evaluated during exercise modes/intensities and beverage ingestion rates associated with GI intolerance. The purpose of the present study was to assess the effects of 80 g/h of a maltodextrin-fructose hydrogel beverage (MFH), compared to conventional carbohydrate sources, on GI symptoms and performance during prolonged running. METHODS: 8 distance runners (26 ± 5 y; VO2max = 65 ± 7 mL/kg/min) completed a prolonged running protocol [90 min at 70% VO2max + an incremental-intensity test to fatigue (TTF)] on three occasions. One of the following beverages was consumed during each trial: a) MFH, b) isocaloric maltodextrin-fructose (MF), or c) isocaloric maltodextrin (MD). Beverages were double-blinded and provided in a randomly counterbalanced order. 125 mL of the beverage was consumed immediately prior to exercise, and at 15-min intervals throughout exercise, providing 80 g CHO/h. Physiological measures (VO2, RER, blood glucose and lactate, heart rate) and GI symptom ratings (nausea, fullness, abdominal cramps) were assessed at 30-min intervals throughout exercise and during the TTF test. Treatment effects were examined using repeated-measures ANOVA’s (treatment x time). RESULTS: VO2, heart rate, and blood glucose increased (p < 0.05) over time during exercise, with no treatment or treatment*time effects. Similarly, all GI symptoms increased in severity over time with no differences between treatments, with the exception that the fullness rating during the TTF was higher in the MF trial (6.2 ± 2.4) versus MD (4.1 ± 3.0). No differences in TTF were observed between MD (551 ± 212 s), MF (555 ± 230 s) and MFH (540 ± 165 s). CONCLUSIONS: Under the present conditions (moderate intensity running while consuming carbohydrate at ingestion rates of ~80 g/h), a carbohydrate hydrogel beverage provided no meaningful effects on physiological responses, gastrointestinal symptoms, or running performance versus conventional carbohydrate beverages.