Fructose supplementation has become a key strategy within sports nutrition for endurance sports such as running, trail running or cycling. When used correctly, it can help you improve performance, delay fatigue and optimize energy replenishment during long training sessions and competitions.
Below, we answer the 10 most frequently asked questions about fructose supplementation in endurance sports.
1. What is fructose and why is it used in endurance sports?
Fructose is a simple carbohydrate that is absorbed in the intestine through a different transporter than glucose.
This makes it possible to increase the total amount of carbohydrates absorbed per hour, which is key in long-duration events such as marathons, ultras or cycling stages.
Naturally, the main sources of fructose are fruits (apples, pears, mangoes, grapes, etc.), dates, honey, nectars and plant saps, as well as vegetables, although in smaller proportions.
2. Why is it recommended to combine fructose with other carbohydrates?
Combining fructose with glucose or maltodextrin makes it possible to use multiple intestinal transporters, which improves absorption and reduces the risk of gastrointestinal discomfort.
Our intestine uses specific transporters to absorb each type of carbohydrate:
- Glucose and maltodextrin are absorbed through the SGLT1 transporter
- Fructose is absorbed through the GLUT5 transporter
When only one type of carbohydrate is consumed (for example, glucose alone), the corresponding transporter may become saturated, limiting the amount of energy the body is able to absorb per hour.
By combining fructose with glucose or maltodextrin, multiple intestinal transporters are activated simultaneously, allowing you to:
- Increase total carbohydrate absorption per hour.
- Maintain more stable energy levels.
- Reduce the risk of unabsorbed carbohydrates causing digestive problems.
3. What is the most commonly used fructose-to-glucose ratio?
The ratios most commonly used in running and cycling are:
- 2:1 ratio (glucose : fructose) At Life Pro, with this ratio you can find Energy Gel with and without caffeine
- 1:0.8 ratio. At Life Pro, you can find Ultra Gel.
These combinations make it possible to reach intakes of 60 to 90 g of carbohydrates per hour, and even more in advanced athletes.
4. In what formats can fructose be supplemented?
Fructose can be consumed in different formats:
- Energy gels
- Isotonic or hypotonic drinks
- Carbohydrate powders
- Energy bars
Each format has advantages depending on the duration of the effort, intensity and digestive tolerance.
5. Is it better to take fructose before, during or after training?
- During exercise: this is the optimal time to maintain energy levels during the race or training session.
- Before: during carbohydrate loading or long sessions.
- After: combined with other carbohydrates to accelerate glycogen replenishment.
6. Can fructose cause digestive problems?
It can cause stomach discomfort if consumed in excess.
That is why it is important to:
- Try it during training, not in competition.
- Gradually adjust the dosage.
- Combine it with glucose or maltodextrin.
Also, in the event of fructose intolerance, fructose-free gel options are available, for example, formulated with maltodextrin and cyclodextrin.
7. How much fructose can be consumed per hour?
In general:
- Up to 30 g of fructose per hour
- Combined with glucose to reach 60–90 g/h in total
Trained athletes may tolerate higher amounts with proper planning.
8- What are the main benefits of fructose supplementation in endurance sports?
Fructose supplementation provides several key benefits in endurance sports such as running and cycling, especially during prolonged efforts at moderate to high intensity.
Its main benefits include:
- Greater energy intake per hour when combined with other carbohydrates such as glucose or maltodextrin.
- Improved intestinal absorption, by using different transporters, which makes it possible to consume more carbohydrates without saturating the digestive system.
- Delayed fatigue, thanks to greater energy availability and muscle glycogen savings.
- Better gastrointestinal tolerance when used as part of a multiple-carbohydrate strategy.
- More stable performance in long events, helping maintain pace for longer.
For this reason, fructose has become a key element within modern endurance sports nutrition strategies.
9. What other supplements can fructose be combined with to improve performance?
Fructose can be combined with different supplements to enhance its ergogenic effect, provided that the strategy is well planned:
- Glucose or maltodextrin: an essential combination to maximize carbohydrate absorption and performance.
- Caffeine: improves perceived exertion, concentration and performance, especially during the final stages of competition.
- Mineral salts and electrolytes: essential for maintaining hydration and preventing cramps.
- Amino acids or BCAA: may help reduce muscle damage during prolonged efforts.
- Beta-alanine: useful in endurance sports involving changes of pace or high-intensity efforts, although its effect is not immediate and requires prior loading.
The key is to adapt the combination to the type of event, duration, intensity and individual tolerance.
10- Can fructose be used during fasted training or when carbohydrate availability is low?
Yes, fructose can be used during fasted training or when carbohydrate availability is low, as long as it is done strategically and with a clear objective within the nutritional plan.