What does 2:1 ratio mean in sports nutrition?

You see it more and more often. The ideal carbohydrate ratio is 2:1. On packaging, blog posts, articles... But what exactly does that mean? And should you take it into account as an athlete?

Dextrose

The term "2:1 ratio" refers to the ratio of glucose over fructose. Glucose (synonymous with dextrose and grape sugar) is the body's most important fuel. Its chemical structure is a 6-ring of carbon atoms and it can further bind to other carbohydrate molecules to start forming chains. Such longer chains are called (depending on their length) maltodextrins or starches.

Fructose

This molecule is a 5-ring of carbon atoms. You mainly find it in fruits and honey. It has a different absorption mechanism in the body than dextrose and can therefore be used as an additional source of energy.

Carbohydrates mainly have their absorption in the small intestine. There, you have several receptors that can absorb glucose and fructose, bringing them to the blood stream. The human body has twice as many receptors for dextrose molecules as for fructose. So we can also absorb twice as much dextrose because of this.

Maximum carbohydrate absorption therefore implies that the composition of carbohydrates you consume has a 2:1 ratio of dextrose:fructose. In this ratio, we can go up to 90g of carbohydrates per hour where with other compositions it is limited to 60g.

For what kind of athletes is the 2:1 ratio actually of interest? Well, especially for the longer endurance athlete. For all sports you do for longer than 3 hours, it might be worth taking a look at this. We'll explain it briefly using an example:

You are a long-distance runner and will soon be running a marathon where you hope to finish it in 4 hours. Average consumption while running is 800 kcal/hour. So a total consumption of 3200 kcal. If you have eaten enough carbohydrates before exercise (carb loading), you will have enough energy in your body to get through the first hour, hour and a half. (800-1200 kcal). After that, carbohydrate intake is a must to start avoiding hunger pangs. This backlash is the body largely switching to fat burning, which is much less efficient for energy production.

So every gram of carbohydrate you can take in means you can continue longer at your desired pace. If you take in 60g of carbs per hour during that marathon, that will give you 960 kcal (4h x 60g/h x 4kcal/g). So still about 1040 kcal that you need to get from your fat burning. When maximising your intake (90g/h), you only need to get 560 kcal from your fat reserves and will therefore delay a hunger pang for much longer.

Well, you're in luck: our isotonic drink Isomix and Energy gels are made to meet the 2:1 ratio. But you'll also find something to your liking among the bars: Endurance Bar (the name actually gave it away) and Energy Fruit also have the 2:1 composition. As long as you stick to these products, you can safely absorb up to 90g of carbohydrates per hour without creating gastrointestinal discomfort.

The 2:1 ratio of carbohydrates is crucial for maximum absorption and becomes more important with increasing duration of the sport you are doing. For all efforts over 3h, it is almost a must.