Best Carbohydrates for Ultra-runners to Take During an Ultramarathon

best carbohydrates for ultra-runners to take during an ultramarathon

In this blog, we will talk about what I believe are some of the best carbohydrates for ultra-runners to take during an ultramarathon.  Keep in mind that a combination of carbohydrates is almost always the best route to go when fueling endurance exercise.  Also, keep in mind that fueling an ultramarathon is different than, say, a marathon.  In comparison, an ultra-runner has a much higher risk of gastrointestinal distress, and risk of palate fatigue.  Additionally, ultras require more carbohydrate intake for longer, are run at a lower intensity, and, ideally, result in a higher percentage of fat being used as fuel.

There are many more differences to consider as well, this is just the beginning.  If you’d like to learn more about that, check out Ultra-Endurance vs. Conventional Endurance.  Let’s dive into the best carbs for ultra-runners.

#1. Cyclic DextrinBest carbohydrates for ultra-runners

Cyclic Cluster Dextrin is the #1 carbohydrate for ultra-runners to take during an ultramarathon, and it wasn’t a hard choice. Cyclic Dextrin has a super-fast gastric emptying time, improves the absorption of other nutrients, leads to virtually no G.I. distress, and improves time to exhaustion. It does all this while decreasing perceived effort. Compared to traditional carbohydrates used during endurance activity, Cyclic Dextrin is in a league of its own. It really is the king of endurance carbs, especially for ultra-runners. Using Cluster Dextrin as a base and combining it with other synergistic and supportive carbs will provide an excellent fuel source for long, sustained energy demands.

#2. Glucose (Dextrose) + Fructose or Sucrose

Glucose and fructose are simple sugars that effectively fuel endurance exercise, especially when used together. They are often used in ratios of 1:1 or 2:1 glucose: fructose. It is not uncommon to see endurance fuels entirely comprised of these two sugars. If you didn’t already know, sucrose, which is literally white table sugar, is simply glucose and fructose bonded together in a 1:1 ratio.

Some athletes and endurance supplement companies will opt to then add more glucose (aka dextrose) to make that ratio 2:1 or close to that. The reason more dextrose is added is that excessive fructose can be particularly irritating to the gut. Some sources suggest that 30 grams/hour of fructose is about the maximum you should use if using glucose and fructose to fuel endurance activity. So, as an ultra-runner aiming to take in 90 grams/hour, this might look like 60 grams of glucose and 30 grams of fructose.

#3. Palatinose (Isomaltulose)

Palatinose is an excellent carbohydrate for ultra-runners primarily due to its ability to improve fat oxidation during endurance exercise. Palatinose is similar to sucrose (table sugar) in that it comprises glucose and fructose linked together with a glycosidic bond. The difference is in the bond itself. The glycosidic bond in Palatinose breaks down significantly slower than does that in sucrose, leading to a slower release of energy and a negligible glycemic impact. The glycemic index of Palatinose is about half that of sucrose. Once the bond is broken down, glucose and fructose are metabolized normally.

Palatinose is broken down slower and doesn’t have the super-fast gastric emptying time of Cyclic Dextrin. Therefore, using it as a sole or primary fuel source might not agree with everyone as it may lead to bloating in higher quantities. Consequently, we believe Palatinose is best in a “supportive” role with other “primary” carbohydrates like Cluster Dextrin or a combination of glucose and dextrose. Remember that Palatinose will still break down into glucose and fructose, so taking into account the total fructose consumed is recommended.

Taking in fructose is important to increase the carbs one can consume as it utilizes a unique transporter that only metabolizes fructose. However, as mentioned previously, taking over 20-30 grams/hour can result in gastrointestinal distress. Like Palatinose, fructose is best in a supportive role.

#4. Maltodextrin

To an extent, maltodextrin can be likened to Cyclic Dextrin. The two are comparable when looking at their positive attributes – fast gastric emptying, high osmolality, and overall a good fuel source for endurance athletes. However, Cyclic Dextrin leads to far less G.I. distress than maltodextrin, more stable blood sugar levels, and significantly increases time to exhaustion.
Unfortunately, all this comes with a cost, with Cluster Dextrin being about 5x the price of maltodextrin.

Maltodextrin also has a much higher glycemic impact than Cyclic Dextrin. This is not in itself a bad thing. Still, Cyclic Dextrin will allow for more supplementary fat oxidation during long endurance efforts as a result. Because of the similarities between the two, it’s likely unnecessary to use both. Instead, one or the other can be mixed with (at the least) some fructose to increase carbohydrate availability. For more information on how Cyclic Dextrin compares to maltodextrin, read – Cyclic Dextrin vs. Maltodextrin for Ultra-Runners.

Summary – The best carbohydrates for ultra-runners to take during an ultramarathon

The best way to fuel endurance exercise is by combining various carbohydrates. Multiple transportable carbohydrate solutions have been shown to lead to better endurance performance than single carbohydrate solutions.

At Ultraverse Supplements, we only opt for the best version of any particular supplement. We don’t have budget options, different quality tiers, etc. We only make what we believe to be the best endurance supplements and don’t use our time or resources to formulate anything less for the sole sake of affordability. Understandably this might mean our supplements aren’t for everyone.

We formulated Proxima C Endurance Fuel specifically to meet the unique demands of ultra-running and other ultra-endurance sports. We start with the best endurance carbohydrate available – Cyclic Dextrin, which makes up over 60% of our four-carbohydrate blend. After that, we use what we believe to be the perfect ratio of dextrose, fructose, and Palatinose to make a blend that was MADE for the long haul.

To learn more about Proxima C Endurance Fuel and why it is the king of ultra-running carbohydrate drinks, check out the Proxima C page. Make sure to click through all the drop-downs.

If you’re looking for the best carbohydrate drink for ultra-runners, you’ve found it.


Proxima C Endurance Fuel





König, D., Zdzieblik, D., Holz, A., Theis, S., & Gollhofer, A. (2016). Substrate Utilization and Cycling Performance Following PalatinoseTM Ingestion: A Randomized, Double-Blind, Controlled Trial. Nutrients, 8(7), 390.
Oosthuyse, T., Carstens, M., & Millen, A. M. E. (2015). Ingesting Isomaltulose Versus Fructose-Maltodextrin During Prolonged Moderate-Heavy Exercise Increases Fat Oxidation but Impairs Gastrointestinal Comfort and Cycling Performance. International Journal of Sport Nutrition and Exercise Metabolism, 25(5), 427–438.
Suzuki, K., Shiraishi, K., Yoshitani, K., Sugama, K., & Kometani, T. (2014). Effect of a sports drink based on highly-branched cyclic dextrin on cytokine responses to exhaustive endurance exercise. The Journal of Sports Medicine and Physical Fitness, 54(5), 622–630.
Takii, H., Kometani, T., Nishimura, T., Kuriki, T., & Fushiki, T. (2004). A Sports Drink Based on Highly Branched Cyclic Dextrin Generates Few Gastrointestinal Disorders in Untrained Men during Bicycle Exercise. Food Science and Technology Research, 10(4), 428–431.
Wilburn, D., Machek, S., & Ismaeel, A. (2021). Highly Branched Cyclic Dextrin and its Ergogenic Effects in Athletes: A Brief Review. Journal of Exercise and Nutrition, 4.

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