Does the Fructose-Glucose Syrup in Sports Drinks Help During Exercise?

Glucose is absorbed mainly via a transporter called SGLT1, while fructose uses a separate transporter called GLUT5. Consuming a large amount of glucose alone saturates SGLT1's capacity, capping how fast it can be absorbed and used. Fructose taken alongside it travels through a different route, so combining the two raises total carbohydrate utilization.

When a single carbohydrate such as glucose is consumed alone during exercise, the rate at which the body can oxidize (use as energy) it caps at roughly 60 g per hour. Consuming more than this doesn't help, because gut absorption can't keep pace — and often leads to gastrointestinal discomfort such as bloating or diarrhea.

Consuming glucose and fructose together, using their separate transporters, has been shown to raise carbohydrate utilization to roughly 90-105 g per hour. In an RCT involving cycling exercise lasting over 2 hours, at the same carbohydrate delivery rate (1.8 g/min), the glucose-plus-fructose condition completed a time trial about 8% faster than glucose alone.

~60 g/hour

Utilization ceiling for a single carbohydrate

~90–105 g/hour

Utilization rate with glucose + fructose combined

~8% faster

Time-trial improvement, mix vs glucose alone

Most of the research demonstrating this effect involves prolonged endurance exercise (such as cycling) lasting over 2 hours. A typical resistance-training session of 30-60 minutes doesn't generate the kind of sustained energy demand where carbohydrate delivery rate becomes the limiting factor, so the same benefit doesn't automatically transfer. This evidence is best understood in the context of long endurance training or race-day fueling.