Carbohydrate Mixes For Enhancing Cycling Performance?

One of the most critical nutrition strategies for performance is fuelling on the bike. This typically refers to consuming adequate carbohydrates to support the work that you’re doing.

When well-fuelled and rested, a trained cyclist can have 2000 kcals/500 grams of carbohydrates stored in their muscles and liver as glycogen. At high to moderate intensities, this is the main fuel used and these stores can become depleted in as little as 90-120 minutes of moderate to high-intensity exercise.

 With the depletion of these glycogen stores comes fatigue/blowing up/ bonking. Therefore, whenever we are likely to deplete these stores, fuelling on the ride can play a significant role in preventing/delaying this.

The current textbook recommendation for fuelling rides longer than 2.5 hours is to aim to consume in the region of 90 grams of carbohydrate an hour, with a lot of interest and hype now in pushing beyond this, with riders in the pro peloton reporting consuming in the region of 120 grams of carbs an hour.

An important consideration when it comes to high carbohydrate intake on the bike is the type of carbohydrate consumed. Not all carbohydrates are absorbed in the same way in the gut, so to achieve high intakes of carbohydrates (i.e. above 60g/hr), we have to use specific blends of certain carbohydrates to ensure the carbohydrate is actually absorbed in the gut. Let me explain.

Up until around 2004, it was always thought that around 60 grams an hour was the maximum amount of carbohydrates that could be absorbed and used by the body from sources consumed during exercise.

Overall, we can burn significantly more than 60 grams of carbohydrates an hour during high-intensity exercise (through a combination of muscle and liver glycogen as well as what we eat on the bike), but when taking on carbs during exercise, 60 grams appeared to be around the maximum that could be absorbed and used from a sports drink when consuming the monosaccharide glucose. Many of the carbohydrates consumed in our diet contain carbohydrates that, through digestion, are broken down into glucose (i.e. rice, pasta, etc).

It was then discovered that by using different types of carbohydrates together, in the form of a combination of glucose and fructose, we could significantly increase the amount of carbohydrates that were absorbed and used by the muscles during exercise to 90 grams an hour. Once research showed this could be beneficial for endurance performance, it then became the new recommendation for endurance athletes.

It was suggested that this increased ability to burn more carbs from external sources was the result of non-competitive absorption of glucose and fructose in the gut. In effect, glucose uses a different transporter in the small intestine (called sodium-glucose transporter 1 – SGLT1 for short) compared to fructose (GLUT5). This then allows the two different carbohydrates to be absorbed through different doorways in the gut so to speak, therefore allowing greater total carbohydrate absorption.

What’s the best ratio?

In recent years, there has been a focus on what is the optimal ratio of glucose to fructose, largely driven by different brands extolling the virtues of their unique formulation. So what is the best ratio?

If you consume less than 60 grams an hour, the ratio of glucose to fructose won’t matter; as long as you consume mainly glucose or maltodextrin (a long-chain form of glucose often used in sports products), all of it will be absorbed. As we know, anything below 60 grams an hour won’t saturate the transport systems in the gut, and therefore, it doesn’t matter what type of carbohydrate or ratio you use.

 The only key consideration here is to avoid anything that solely contains the fruit sugar fructose as, on its own, it’s likely to cause significant stomach issues (as I can personally vouch for 💩💨). While they won't do any harm, this also means there is little need for specifically formulated sports nutrition products when consuming less than 60 grams an hour. Many normal foods will suffice.

 When consuming above 60 grams of carbohydrates per hour, we need to use a combination of glucose and fructose. At around 90 grams an hour, a ratio of 2 parts glucose to one part fructose appears to be best. So, around 60 grams of glucose and around 30 grams of fructose per hour. This has been shown to result in a high oxidative efficiency, which basically means that almost all of the carbohydrate that is consumed is used as fuel, meaning that very little is backing up in the gut, so it is unlikely to cause any stomach issues.

When consuming 90 grams an hour+, as we’ve covered previously (https://www.fueltherideacademy.com/blog/should-cyclist-fuel-with-100-grams-of-carbohydrate-per-hour), we’re not big fans of this approach, as it’s not likely to benefit performance for most athletes and comes with significant risks of gastrointestinal distress.

With anything above 90 grams an hour, we know we can’t absorb any more than 60 grams of glucose, so any additional carbohydrate needs to come from fructose. As such, if we’re looking to consume more than 90 grams an hour, we need a ratio of glucose to fructose that is closer to unity, i.e. 1:0 – 0.8 (as now used in products like Science In Sport Beta Fuel and Styrkr) or 1:1, as found in products that contain sucrose (table sugar) which is a 1:1 ratio of glucose to fructose.

 This therefore means that athletes can formulate a sports drink using simple table sugar and have a high performance drink formulation as effective as an off the shelf product.

There is therefore no magical ratio of glucose to fructose, but there appears to be specific considerations around the dose of carbohydrate consumed and the ratio to use. For most, using any glucose: fructose product up to 90 grams an hour is absolutely fine.

Coach Ben

Reference - https://pubmed.ncbi.nlm.nih.gov/26373645/