Sports gels are one of the most widely used nutritional strategies by endurance athletes to maintain performance during prolonged training sessions and competitions. However, not all gels have the same formulation. One of the main differences lies in the type and combination of carbohydrates they contain.
So why do manufacturers combine different carbohydrate sources instead of using just one? The answer lies in how our bodies absorb and utilize these nutrients during exercise.
The role of carbohydrates during exercise
During moderate- to long-duration exercise, muscle glycogen stores gradually become depleted. As these stores decline, the availability of ingested carbohydrates becomes increasingly important to sustain exercise intensity and delay fatigue.
For this reason, current sports nutrition guidelines recommend carbohydrate intake during endurance events, especially when exercise lasts longer than 60 to 90 minutes.
The limit of intestinal absorption
For many years, it was believed that the body could absorb approximately 60 g of carbohydrates per hour. This limitation is primarily related to the capacity of the intestinal transporter SGLT1, which is responsible for absorbing glucose and maltodextrin.
When only glucose or maltodextrin is consumed in large amounts, this transporter can become saturated, reducing absorption efficiency and increasing the likelihood of gastrointestinal discomfort.
This understanding led to the development of multiple transportable carbohydrate strategies.
Why combine different carbohydrates?
Different carbohydrates are absorbed through different intestinal transporters.
While glucose and maltodextrin primarily rely on the SGLT1 transporter, fructose is absorbed through GLUT5.
By combining these carbohydrate sources, the body can utilize multiple absorption pathways simultaneously, increasing the total amount of carbohydrate delivered to the bloodstream and made available for energy production during exercise.
This strategy provides several benefits, including:
- Greater energy availability during prolonged exercise.
- Higher rates of exogenous carbohydrate oxidation.
- Reduced reliance on muscle glycogen stores.
- Lower risk of saturating a single intestinal transporter.
- Improved gastrointestinal tolerance when combined with proper gut training.
Today, numerous studies show that athletes can successfully utilize carbohydrate intakes above 90 g per hour when multiple transportable carbohydrates are combined with appropriate gut training.
The most common carbohydrate combinations
Several carbohydrate ratios have been investigated over the past decade.
The traditional approach combines maltodextrin and fructose in a 2:1 ratio, a strategy that demonstrated excellent results for many years.
More recently, research has shown that ratios close to 1:0.8 also provide highly efficient absorption and may offer excellent gastrointestinal tolerance at high carbohydrate intake levels.
The optimal ratio depends on the athlete's nutritional strategy, target carbohydrate intake per hour, and individual characteristics.
Where does isomaltulose fit in?
In addition to glucose, maltodextrin, and fructose, some sports gels also include isomaltulose.
Isomaltulose is a slowly digested disaccharide that provides a more gradual release of glucose into the bloodstream compared with rapidly absorbed sugars.
When combined with other carbohydrate sources, it may help provide a more sustained energy supply throughout exercise without replacing the rapidly available carbohydrates required during higher-intensity efforts.
How is this strategy applied in sports gels?
Sports gels available on the market use different carbohydrate combinations depending on their intended purpose.
For example, some gels designed for everyday training combine maltodextrin, fructose, and isomaltulose, aiming to provide both rapid and sustained energy release.
This is the case with Every Day, from Z2 Performance, which contains approximately a 2:1:1 ratio of maltodextrin, fructose, and isomaltulose, along with sodium to support electrolyte replacement during exercise.
On the other hand, products designed to deliver larger amounts of carbohydrate per serving may use only maltodextrin and fructose, such as Load Up, which is formulated using a 1:0.8 ratio, consistent with the latest scientific evidence for high carbohydrate intake during prolonged endurance exercise.
Regardless of the formulation, the goal remains the same: to optimize carbohydrate availability and maximize intestinal absorption during exercise.
Quantity matters too
Choosing a gel with an effective carbohydrate blend is only part of the strategy. The amount consumed each hour also plays a crucial role.
Current recommendations generally suggest:
- Up to 60 minutes: carbohydrate intake is usually unnecessary.
- Between 1 and 2.5 hours: approximately 30–60 g of carbohydrates per hour.
- More than 2.5 hours: around 60–90 g per hour.
- During very long endurance events, well-trained athletes may tolerate intakes of up to 120 g per hour when using multiple transportable carbohydrates combined with gut training.
These recommendations should always be individualized and tested during training rather than introduced for the first time on race day.
Conclusion
The combination of different carbohydrates in sports gels is based on well-established physiological principles. By utilizing multiple intestinal transporters, athletes can increase carbohydrate absorption, improve energy availability, preserve glycogen stores, and reduce the likelihood of gastrointestinal discomfort during prolonged exercise.
Ultimately, selecting the right gel is only one component of a successful fueling strategy. The total carbohydrate intake, timing, individual tolerance, and race-specific nutrition plan all contribute to maximizing endurance performance.
