TLDR: Combining glucose and fructose, known as multiple transportable carbohydrates enhances carbohydrate absorption and oxidation during endurance events. This strategy allows athletes to consume 60–120g of carbs per hour, improving performance while reducing gastrointestinal discomfort. Incorporate this approach into training to adapt your gut and optimise race-day fuelling.
Fuelling effectively during endurance events can be the difference between a personal best and crashing and burning before the finish line. A lot of athletes know that they should be consuming carbohydrate during their runs and this can absolutely be a game changer, but the type and combination of carbohydrates you consume can also give you an additional edge over your competition. Multiple transportable carbohydrates have become a cornerstone of sports nutrition and have transformed how athletes approach fuelling during long races and intense training sessions. In this article, we’ll explore what multiple transportable carbohydrates are, their benefits for endurance athletes, and how you can integrate them into your training for optimal performance.
What Are Multiple Transportable Carbohydrates?
Multiple transportable carbohydrates refer to a combination of different types of carbohydrates, most commonly glucose and fructose, that are absorbed through specific transporters in the digestive system, hence the name.
This strategic combination allows for a greater rate of carbohydrate absorption and oxidation than using glucose alone [1-3]. We have some pretty good research indicating that 60g/hour for most people is the most glucose we can comfortably digest and absorb without issues [3, 4]. The reason for this is you have specific transporters in your gut that take up glucose and once you are hitting 60g/hour these transporters become saturated, they simply can’t take up any more than this. The good news is you also have specific transporters that take up the other sugar we are discussing, fructose, which is commonly found in fruit and honey. So when you are hammering your digestive system with only glucose, those transporters are working overtime whilst your fructose transporters are sat with their hands in their pockets waiting for something to do. By utilising both pathways simultaneously, athletes can push their carbohydrate absorption rates beyond the limits of a single source, leading to enhanced carbohydrate availability and reduced risk for digestive issues during prolonged exercise[5]
Benefits of Multiple Transportable Carbohydrates for Endurance Athletes
Having multiple transportable carbohydrates as a part of your fuelling strategy offers several key benefits that make them particularly effective for endurance athletes:
- Increased Carbohydrate Oxidation: When glucose and fructose are consumed together, studies have shown that the rate of carbohydrate oxidation can be significantly higher than when glucose alone is used. This means more energy is available to your muscles, allowing you to sustain higher intensities for longer periods[1, 2]
- Enhanced Performance: Research consistently demonstrates that athletes who consume multiple transportable carbohydrates during exercise perform better in time trials and endurance events. For example, a study found that cyclists who consumed a glucose-fructose blend completed a time trial 8% faster than those who consumed glucose alone[6].
- Improved Fluid Delivery: Another advantage of multiple transportable carbohydrates is their ability to enhance fluid delivery by speeding up gastric emptying[7].
How to use Multiple Transportable Carbohydrates in Your Training
To really get the benefits from multiple transportable carbohydrates, it’s essential to incorporate them both into your training and racing routines. Here’s how:
- Dosage Recommendations: Aim to consume 60-110 grams of multiple transportable carbohydrates per hour during long-duration exercise. This dosage is going to provide you with a notable performance benefit.
- Product Selection: There are various products on the market designed to deliver multiple transportable carbohydrates. Look for sports drinks, gels, and bars that list a combination of glucose, fructose in their ingredients. If you find a product that use maltodextrin instead of glucose that’s fine. Although its technically an oligosaccharide its broken down into glucose very quickly so you can think of the two being practically the same. Some popular options include brands that specifically formulate their products with a 2:1 or 1:0.8 ratio of glucose to fructose.
- Training the Gut: Some athletes may experience initial gastrointestinal discomfort when they first fuelling their training sessions, especially as they move into higher intakes of carbohydrate per hour. It’s important to practice using these products during your training sessions to train your gut. This ensures that your body can handle the carbohydrate load without gastrointestinal distress on race day. Start by gradually introducing these products into your routine and slowly increase the dosage as your gut adapts.
How Much do the Ratios of Multiple Transportable Carbohydrates Matter?
Different gels, bars and drinks will use different ratios with the 2:1 or 1:0.8 ratios being the most common and evidence based. The important takeaway is that both combinations have been shown to enhance carbohydrate absorption and oxidation.
Some recent research has suggested the ratio of 1:0.8 provides additional benefits versus the 2:1 ratio from both a gastrointestinal comfort and performance standpoint[1, 2], which is most likely due to more efficient intestinal absorption of both monosaccharides. For this reason I typically nudge my athletes towards this ratio.
Do I have to Use Gels and Bars to get Multiple Transportable Carbohydrates?
No. You can use regular food instead of gels and bars for fuelling during endurance events. Foods like fruit and honey contain both glucose and fructose. This might be your preference from a taste and/or texture perspective and could be more cost effective too. If cost is the main driver, my guide to making a homemade sports drink shows how to mix your own at either ratio. You should consider a few things before doing this though.
During high-intensity exercise, the digestive system can struggle to break down and absorb more complex foods, especially foods higher in fibre and fat. Gels and bars are formulated to be easily digestible, reducing the risk of gastrointestinal discomfort. Gels and bars are designed and packaged for ease of use during exercise. They are lightweight, easy to carry, and quick to consume, which is just really handy. Sports products are designed to provide exactly what you need in terms of carbohydrate, electrolytes, and sometimes caffeine. Whilst not impossible, this can be difficult to replicate with whole foods. Use gels, bars and drinks takes a lot of the guesswork out of your fuelling strategy.
The Future of Carbohydrate Supplementation
The science in this area will continue to evolve, with ongoing research exploring even more efficient carbohydrate combinations and innovative ways to deliver these nutrients during exercise. Additionally, emerging technologies such as continuous glucose monitors are beginning to provide real-time on blood glucose levels. I’m not sold on this tech as a commercial product for athletes, for a variety of reasons, but I could see it being useful from a research perspective.
Conclusion
Multiple transportable carbohydrates are a fairly simple but powerful tool for endurance athletes, offering increased carbohydrate oxidation, enhanced performance, and improved hydration with reduced gastrointestinal distress, what more would you want! By incorporating these carbohydrates into your training and upcoming races, you could be well on the way to your next PB.
