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The 2:1 ratio: what is it?

Jan 22, 2019 4:15:16 PM
3 min read

What is the 2:1 ratio?

As you learn more about triathlon nutrition, you will undoubtedly come across the term 2:1 ratio when isotonic drinks or energy gels are discussed.

The 2:1 ratio refers to the specific proportions of carbohydrates found in the product, namely a ratio containing twice as much glucose as fructose.

It quite simply means your product contains 2 different types of sugar / carbohydrate molecules: glucose and fructose, in that specific 2:1 ratio.

Why is the 2:1 ratio important? 

There are 2 important reasons why the 2:1 ratio of glucose to fructose matters:

  • performance
  • digestive comfort

Both are very important considerations for the serious triathlete, and both find their root in the digestion of carbohydrates.

For a long time, it was generally accepted that the human body could digest about 60 grams of carbohydrates per hour, especially under conditions of intense stress like during a Ironman run. In a way, this is still true. The body transports carbohydrates from the intestines to the blood through 2 membranes. To pass these membranes, carbohydrates need a transporter. Look at it as your carbs needing a taxi to get them to their destination.

Glucose uses a transport protein called SGLT1 for absorption, which becomes saturated at about 60 grams of glucose per hour. Consuming more glucose than 60 grams per hour would not result in greater carbohydrate uptake and oxidation, and as a result would not yield increased performance. On the contrary, it would lead to the accumulation of undigested carbohydrates in the gut. This could very likely lead to cramping and diarrhea!

As you may have learned from our e-book on racing nutrition, your body can only store a limited amount of glucose (in the form of glycogen) in the muscles and liver. Once your glycogen stores are depleted, your performance can suffer (dramatically). This is often referred to as 'hitting the wall' or 'bonking'.

So it is important to be able to take in as many carbohydrates as possible during extended efforts, such as an Ironman or Ironman 70.3.

Researchers have been studying how to increase the hourly uptake of carbohydrates. In 2004, Dr Roy Jentjens at the University of Birmingham published the first study, indicating that by adding fructose (a sugar typically found in fruit) to the mix, the total uptake and oxidation of carbs could be increased by as much as 25%!

The reason for this is that fructose uses an all together different transporter to pass the intestines, namely GLUT5.

2 to 1 ratio

So when the glucose transporter gets saturated at about 60 grams per hour, the fructose transporter kicks in, and allows the body to burn more sugars, increasing performance without causing gastrointestinal discomfort such as cramps.

Does it increase performance?

In short: yes! Being able to provide the body with more fuel, especially during longer efforts, will increase performance, as concluded extensively by professors such as Asker Jeukendrup in this study.

Performance was increased by 16% as compared to subjects not taking in carbohydrates, and by 7,6% compared to athletes taking a glucose-only drink. Indeed, that is a major improvement!

How much carbohydrates can I take in a 2:1 ratio?

Research and real-life feedback indicate that consumption of 90 grams of carbohydrates per hour is possible, as long as you train your body to absorb this kind of intake. The gut adapts itself when confronted with higher intakes, but it requires training like any other organ.

Some athletes have even higher tolerances, and some world-class athletes experiment with the amount of fructose they can tolerate, up to ratios of 1:1 and 120 grams of total carbohydrates per hour.

However, as a general rule, aim at taking up to 90 grams of carbohydrates per hour, depending on the length of your effort. This simple infographic can help you determine the right amount.

Nutrition Planner

Does HIDDIT follow the 2:1 ratio concept?

Yes! Our Isotonic drink and Energy Gels both contain the science-based 2:1 ratio of glucose to fructose, to optimize performance and digestive comfort.

Want to give it a try? Visit our shop now!

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