Last week, I highlight carbohydrate requirements during exercise (if you missed it, click here). As discussed, this can range from 30-90 grams of carbohydrates per hour of exercise. The term “carbohydrates” is broad, as there are many types of carbohydrates. Does it matter what type of carbohydrate you consume during exercise? Read on to find out.
When it comes to carbohydrates during exercise, we classify carbohydrates based on how fast they are oxidized by the body. Fast carbohydrates are quickly absorbed and used by the muscle as an energy source. Fast carbohydrates include:
- Glucose, sucrose, maltose, maltodextrins and amylopectin
On the other hand, slow carbohydrates are slower at being absorbed and used by muscles as an energy source. Slow carbohydrates include:
- Fructose, galactose, isomaltulose, amylose, and trehalose
As discussed last week, intestinal absorption of carbohydrates is the limiting factor in being able to use carbohydrates as energy. As a result, carbohydrates used during exercise should be “fast carbohydrates” such as glucose, sucrose and maltodextrins. Most specialized sport products utilize fast carbohydrates. For instance, if you look at a bottle of Gatorade, you will see the first two ingredients are: sucrose and dextrose (which is glucose). Both of these are fast carbohydrates and rapidly oxidized by the body.
However, even the fast carbohydrates have an upper limit absorption rate of 60 grams/hour, so how can there be a recommendation for up to 90 grams of carbohydrates per hour of exercise? This is where the slow carbohydrate, fructose comes in. Fructose uses a different transporter in the intestine than the fast carbohydrates. By consuming fructose in addition to the fast carbohydrates, up to 90 grams per hour of carbohydrates can be absorbed because two different transporters are being utilized. Most sport products such as gels are specially formulated in this way. For instance, if you look at the ingredients list on GU gels, you will notice maltodextrin listed first followed by fructose.
Yes, the type of carbohydrates consumed during exercise needs to be considered. If you are consuming less than 60 grams/hour then aim for the fast carbohydrate sources. If you’re going over this 60 grams/hour, then aim for a carbohydrate source that contains a fast carbohydrate in addition to fructose.
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