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Multiple Transportable Carbohydrates

(They're not as fancy as you think).

What are they, and can they help improve sports performance?

When it comes to fuelling your body for intense exercise, not all carbohydrates are created equal. Understanding the science behind how different carbohydrates are absorbed and used can help you optimise your performance, especially during prolonged activities and endurance exercise lasting longer than 150 minutes.

Sucrose |Table sugar| Single Carbohydrate

Single Carbohydrates and their Limitations

Single carbohydrates refer to the use of one type of carbohydrate, such as glucose, sucrose, or fructose as the sole source of energy during exercise. These carbohydrates are absorbed through a specific transporter in the intestines, limiting the rate at which they can be oxidised and used for energy.

Rapidly oxidised carbohydrates like glucose, maltodextrin, and sucrose are oxidised at a rate up to 1 g/min, but no higher. This limitation is related to how these carbohydrates are absorbed in the intestines through a transporter called SGLTI. Once this transporter becomes saturated, the delivery of glucose to the muscles cannot be further increased.

Other carbohydrates, such as fructose, are oxidised at even lower rates due to slower digestion and absorption [1]. This leads to a bottleneck in delivering energy to the muscles, especially during prolonged exercise.

It was commonly believed therefore, that the maximum carbohydrates an individual could oxidise or burn was about 60 grams per hour, using one of the carbohydrate sources mentioned above.

Breaking this barrier 60 grams per hour limit has been a key focus in sports nutrition research in previous years.

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Enter Multiple Transporter Carbohydrates

Multiple transporter carbohydrates sounds like a fancy term for a special type of carbohydrate. It's not. It's simply using a mix of carbohydrates that can be absorbed by multiple transporters in the gut.

A study in the early 2000s by Jentjens et al found that combining different types of carbohydrates could break through this 60g / hour barrier. By saturating the SGLTI transporter with glucose and adding another type of carbohydrate - fructose, the athletes could burn more carbohydrates. This is because fructose uses a completely separate transporter in the gut called GLUT-5. [2]

This was a significant discovery, as it allowed for higher oxidation rates of up to 76 grams of carbohydrates per hour.

Further studies and reviews confirmed that consuming multiple transportable carbohydrates resulted in up to 75% higher oxidation rates than using carbohydrates that rely solely on the SGLTI transporter. This approach was effective using different products such as drinks and gels [3].

Cyclists Exercising at High Intensity

So, do multiple transporter carbohydrates improve performance?

While the science behind multiple transportable carbohydrates is fascinating, the real question for athletes is how it affects performance.

Several studies have linked increased carbohydrate oxidation rates with delayed fatigue and improved exercise performance.

In one study, subjects who consumed a glucose-fructose mixture during a 5 hour bout of moderate-intensity cycling reported lower perceived exertion and were able to maintain pedal cadence better than subjects who consumed just glucose [4].

Subsequent studies where subjects used multiple transportable carbohydrates have reported reductions in fatigue and improvements in exercise performance.

The benefits of using multiple transportable carbohydrates are multifaceted. Not only do they allow for higher oxidation rates, leading to more energy, but they also contribute to delayed fatigue, improved exercise performance, and better maintenance of effort during long sessions. These advantages translate into real-world gains for athletes, enabling them to push harder and go further in their training and competition.

Keep in mind that using multiple transportable carbohydrates effectively requires that the exercise session lasts at least 2.5 hours, and that you adhere to a strict carbohydrate intake (usually around 90 g/h).

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How do I apply this to my training and racing nutrition?

  • Choose the Right Carbohydrates: Understanding the types of carbohydrates and how they are absorbed can lead to more effective fuelling strategies. For example, athletes can consider using glucose polymers for increased carbohydrate content without increased osmolality, which can reduce the risk of gastrointestinal distress.
  • Understand Osmolality: Learn more about osmolality and its importance in our article about Carbohydrate types and exercise.
  • Train Your Gut: Many athletes struggle to get to the upper carbohydrate intake level of 90 g/hour for various reasons. Gut training is a strategy that you can use to increase the amount of carbohydrates that your body can tolerate.
  • Experiment with Products: Experiment with different products, and be aware that not all exercise requires a carbohydrate only approach. Gels and sports drinks may see your through a road half marathon or marathon, but for events lasting many hours, other factors like taste fatigue come in to play. Try incorporating real foods like Roam Energy Nut Butter into your training routine, to find what works best for you.

References

[1] Burke Louise et al.Clinical Sports Nutrition. 6th ed. McGraw-Hill Education/Australia 2021.

[2] https://doi.org/10.1152/japplphysiol.00974.2003
Jentjens, Roy L P G et al. “Oxidation of combined ingestion of glucose and fructose during exercise.”Journal of applied physiology (Bethesda, Md. : 1985)vol. 96,4 (2004): 1277-84.

[3] https://doi.org/10.1249/MSS.0b013e3181e0efe6
Pfeiffer, Beate et al. “CHO oxidation from a CHO gel compared with a drink during exercise.”Medicine and science in sports and exercisevol. 42,11 (2010): 2038-45.

[4] https://doi.org/10.1152/japplphysiol.00981.2004
Jeukendrup, Asker E et al. “Exogenous carbohydrate oxidation during ultraendurance exercise.”Journal of applied physiology (Bethesda, Md. : 1985)vol. 100,4 (2006): 1134-41.