Exogenous CHO oxidation with glucose plus fructose intake during exercise

Area of Science:

• Sports nutrition
• Exercise physiology
• Carbohydrate metabolism

Background:

• Endurance athletes often use carbohydrate (CHO) ingestion to sustain performance.
• Glucose and fructose are common CHO sources, but their combined metabolic effects require further investigation.
• Understanding exogenous CHO oxidation rates is crucial for optimizing fueling strategies.

Purpose of the Study:

• To compare exogenous carbohydrate oxidation rates between glucose alone and a combined glucose-fructose solution.
• To determine if a 0.8 g/min glucose and fructose mixture enhances exogenous CHO oxidation compared to glucose alone.

Main Methods:

• Seven trained male cyclists completed 150 minutes of cycling at 65% VO2max.
• Subjects ingested solutions of glucose (GLU), glucose plus fructose (GLU + FRU), or water (WAT).
• 13C-labeled corn-derived glucose and fructose were used to quantify exogenous CHO oxidation.

Main Results:

• Peak exogenous CHO oxidation rates were similar for GLU (0.60 g/min) and GLU + FRU (0.57 g/min).
• Average exogenous CHO oxidation rates during the final 90 minutes were also not significantly different between GLU (0.58 g/min) and GLU + FRU (0.56 g/min).

Conclusions:

• Ingesting moderate amounts of glucose plus fructose does not increase exogenous CHO oxidation compared to an isocaloric amount of glucose alone.
• These findings suggest that for exogenous CHO oxidation, a combined glucose-fructose strategy at these rates offers no advantage over glucose alone.