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It is well established that carbohydrate consumption during a marathon is associated with improved performance. This is why many runners take gels during their race, but how many should they take and when?
High-quality meta-analyses and intervention studies show a positive relationship between carbohydrate consumption and performance during an endurance effort of more than one hour. This means that greater carbohydrate intake during exercise results in better performance than lower intake.
Sports products contain different types of rapidly absorbed sugars: Glucose, maltodextrin and fructose. The latter is absorbed using a different carrier, via the liver. In theory, the intestine is able to absorb up to 60g of glucose or maltodextrin per hour and 30g of fructose per hour, for a total of 90g of carbohydrates using different carriers. The form of carbohydrate doesn’t matter. That is to say that consuming carbohydrates in the form of liquid, gels, or jujubes has a similar effect on performance.
| Effort Duration | Carbohydrate intake during exercise |
| 1.5 to 2 hours | 30g/hour |
| 2 to 3 hours | 60g/hour |
| 3 hours or more | 90g/hour using different carriers |
It should be noted that these amounts are independent of body weight and should be adjusted downwards for those running at a slower speed. Knowing that a gel usually contains 25 to 30g of carbohydrates, it is therefore recommended to consume one to two per hour, and up to three per hour for ultra-endurance runners, depending also on the amount of sports drinks consumed (which also contain sugar). The first gel can be consumed from 20 to 45 minutes from the start of the race.
Many runners are scared to eat that much sugar during their race, by fear of having digestive issues. A study published in the International Journal of Sport Nutrition and Exercise Metabolism evaluated the practical implementation of carbohydrate nutritional recommendations during a marathon. 28 runners participating in the Copenhagen Marathon were divided into two groups. Runners in the experimental group consumed the equivalent of three gels per hour with water, sodium, and caffeine, while runners in the control group consumed whatever they wanted. Both groups practiced their nutritional strategy for five weeks prior to the marathon. Runners who followed the scientific recommendations did not experience any gastrointestinal disturbances and ran an average of 4.7% faster than the runners in the control group, for an average marathon time of 3:38:31 versus 3:49:26. Of course, it is not possible to draw conclusions from a single study, especially since these results may also be related to the consumption of caffeine, water or other factors. However, the results suggest that it is possible to consume carbohydrates during a race in accordance with the recommendations without experiencing gastrointestinal discomfort, and that this may help improve performance.
The amount of carbohydrates to be consumed during a race depends on the duration and intensity of the effort as well as the tolerance of the runner. It is possible to train one’s ability to use carbohydrates during effort and thus improve one’s tolerance. When you get used to consuming carbohydrates during exercise, the number of carbohydrate carriers in your body increases, making it possible for you to absorb more carbohydrates at a time. On the contrary, when we are not used to it, our ability to absorb carbohydrates is lower, which can cause gastrointestinal problems such as bloating, nausea and diarrhea. Thus, it is crucial to practice your nutritional strategy ahead of time and during your training period, at least once a week, for long outings or intense trainings. Our body can take several weeks to adapt, hence the importance of starting well before the date of the race. It is also important to experiment with different types of drinks and gels to find the ones that work for you, as their effects can vary from a person to another. Some people may be more sensitive to fructose, especially people who suffer from irritable bowel syndrome (IBS) or runner’s diarrhea. In this case, it would be better to choose gels that do not contain fructose.
Don’t hesitate to try one of our homemade energy gel recipes :
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