Glucose:fructose ratio

Glucose: fructose ratio describes the proportion of glucose (or glucose-based polymers such as maltodextrin) to fructose in a carbohydrate drink or gel. Glucose and fructose are absorbed in the small intestine via different transporter proteins, and they contribute to energy supply in distinct ways. When the ratio is balanced correctly, these sugars can be consumed at high rates without causing gastrointestinal problems or leaving unabsorbed carbohydrate in the gut.

How glucose and fructose work together

The intestine uses the sodium–glucose cotransporter 1 (SGLT1) to absorb glucose, and this transporter becomes saturated when ingestion reaches about 60 g of glucose per hour. If only glucose is provided, exogenous carbohydrate oxidation rarely exceeds 1 g per minute, which limits energy availability during prolonged exercise. Fructose uses a different transporter (GLUT‑5) and is absorbed independently of sodium. Combining glucose with fructose or maltodextrin allows both transporters to operate simultaneously, raising total carbohydrate oxidation above 1 g min⁻¹ and increasing fluid absorption compared with glucose-only solutions. Studies of endurance athletes consuming a 2:1 glucose‑fructose blend at high intake rates (around 78–90 g h⁻¹) report greater exogenous carbohydrate oxidation, improved fluid delivery and slightly better performance compared with glucose alone. The 2:1 ratio saturates the SGLT1 transporter with 60 g h⁻¹ of glucose and provides roughly 30 g h⁻¹ of fructose, delivering about 90 g h⁻¹ of total carbohydrate and reducing the risk of excess fructose accumulating in the gut. Emerging research has investigated alternative ratios such as 1:0.8, but these have not consistently shown performance benefits and may reduce fat oxidation or increase gastrointestinal stress at lower intake rates.

Finding the right blend for long efforts

Athletes use different glucose: fructose ratios depending on the duration and intensity of their events. For long races lasting over two hours, a drink or gel containing about two parts glucose or maltodextrin to one part fructose allows an athlete to ingest 90 g of carbohydrate per hour with fewer stomach issues. For example, consuming 60 g of glucose (often from maltodextrin) and 30 g of fructose per hour provides immediate energy through glucose and secondary fuel through fructose after it is converted by the liver. During ultramarathons or Ironman races, some athletes experiment with slightly higher fructose proportions to exceed 90 g h⁻¹, but this strategy requires careful gut training and may not suit everyone. For shorter efforts or lower intake rates (under 60 g h⁻¹), a 2:1 blend offers no clear advantage over pure glucose and may not be necessary. Regardless of the ratio, mixing multiple sugars with moderate sodium and water helps maintain hydration and reduces the likelihood of gastric distress.

Efficient fueling is about balancing energy delivery with comfort. A well-chosen glucose: fructose ratio maximises carbohydrate availability by saturating the intestine’s glucose transporters and taking advantage of fructose absorption pathways. Most athletes find that a 2:1 blend of glucose or maltodextrin to fructose supports high carbohydrate intake and steady energy during long endurance events without upsetting the stomach.

Related Terms: Carbohydrate per hour, Intestinal absorption, Gastric emptying, Carbohydrate periodization, Palatability