Endurance nutrition has evolved significantly over the past few decades. We now know that consuming both glucose and fructose improves performance compared to glucose alone.
But it’s not enough to just consume both carbohydrates—you also need to get the ratio right.
This article breaks down the ideal glucose-to-fructose ratio and why so many sports fueling brands still get it wrong.
Why Glucose Alone Isn’t Enough
Glucose is the body’s preferred energy source, which is why early fueling products relied on it exclusively. It’s absorbed in the intestines via the SGLT1 transporter. However, there is a limit to how much glucose this transporter can absorb at once.
Fructose, on the other hand, is absorbed through a different transporter—GLUT5. By consuming fructose alongside glucose, athletes can absorb more total carbohydrates per hour, leading to better fueling.
Numerous studies confirm that a combination of glucose and fructose enhances endurance performance. The logic is simple:
More carbohydrates = more energy = better performance.
For a deeper dive into the science behind fueling, check out our Fueling Guide.
The 2:1 Ratio—And Why It Falls Short
Early research by Asker Jeukendrup suggested that glucose absorption maxes out at 60g per hour and fructose at 30g per hour. This led to the widely accepted 2:1 glucose-to-fructose ratio, which many sports nutrition brands still use today.
However, this assumption is overly simplistic.
First, researchers don't actually measure carbohydrate absorption—they measure oxidation rates and infer absorption from those results. But oxidation and absorption aren’t always the same.
Second, individual differences, training adaptations, and environmental factors all influence how much glucose and fructose an athlete can process.
In reality, oxidation rates likely exist within these ranges:
- Glucose: 30g–80g per hour
- Fructose: 20g–60g per hour
So, if the 2:1 ratio isn’t optimal, what is?
Evidence Shows a 1:0.8 Ratio Is Ideal
Research by O’Brien, Rowlands, and others has tested different carbohydrate ratios in real-world endurance scenarios. The results consistently show that a 1:0.8 glucose-to-fructose ratio outperforms the traditional 2:1 ratio.
This suggests that the 2:1 guideline was based more on theoretical absorption. While 2:1 is better than glucose alone, the research shows that 1:0.8 offers even greater benefits:
1. Enhanced Carbohydrate Oxidation
Studies show that a 1:0.8 ratio leads to higher carbohydrate oxidation rates, meaning athletes likely convert more of what they consume into usable energy.
2. Improved Performance
A 1:0.8 ratio has been linked to higher peak power and increased time until exhaustion, crucial factors in endurance sports.
3. Faster Absorption
Some evidence suggests that 1:0.8 enhances carbohydrate and fluid absorption in the jejunum (a section of the small intestine), leading to better hydration and energy availability.
4. Reduced Gut Discomfort
One of the biggest advantages of the 1:0.8 ratio is its lower risk of gut distress—a common issue for endurance athletes. Faster carbohydrate and fluid absorption reduces bloating, cramping, and nausea.
GI issues are very common with athletes and often the reason for race drop-outs.
Why Many Brands Still Use 2:1
Despite clear evidence supporting 1:0.8, many sports nutrition brands continue to use a 2:1 ratio. This is largely due to:
- Industry inertia: The 2:1 ratio was the gold standard for years, and change is slow.
- Manufacturing limitations: Some brands stick to old formulations rather than reformulating.
- Marketing habits: Consumers are familiar with 2:1, making brands hesitant to shift messaging.
Does the 1:0.8 Ratio Really Make a Difference?
For elite athletes, the improved carbohydrate absorption and oxidation rates of 1:0.8 can significantly enhance performance. This is why many professionals have already adopted it for both fueling and recovery.
For amateur athletes or those consuming less than 60g of carbohydrates per hour, the difference in performance may be negligible. However, the reduced risk of gut issues makes 1:0.8 a smart choice for anyone fueling during endurance events.
Bottom Line: Use a 1:0.8 Ratio for Maximum Performance
Research clearly shows that a 1:0.8 glucose-to-fructose ratio enhances carbohydrate absorption, reduces gut issues, and improves endurance performance.
That’s why Nduranz uses the 1:0.8 ratio across its entire line of fueling and recovery products—to provide athletes with the fuel they need to go farther and faster.
Want to fine-tune your fueling strategy? Check out our Fueling Calculator or read our Science-Based Guides.