A number of questions need to be answered before nutritional advice can be given to an athlete. How much fuel (energy) does a sportsperson need? Which fuels are preferred? What about the proportion between carbohydrate, fat and protein? What roles do the vitamins and minerals play? In this article more information on the recommended carbohydrate intake.
Carbohydrates consist of one or more sugar molecules, for example glucose. Glucose is an important fuel for the body, in particular for the brain and nervous system, as well as for muscle. Glucose is stored in the muscles and liver in the form of glycogen. This supply is limited and therefore has to be replenished on a daily basis and after exercise. The body can produce glucose from protein, but it is mainly obtained through carbohydrate from food.
Dietary advice for athletes can be based on general nutritional advice in which 50% of the total energy intake (en%) consists of carbohydrates. (1) For an adult woman with an energy intake of 2,000 kcal this would amount to 250 grams carbohydrate per day (50% of 2,000 kcal = 1000 kcal = 250 grams carbohydrates).
More specific nutritional recommendations for athletes provide guidance for carbohydrate intake in terms of grams per kilogram body weight. A daily intake of 5-7 grams carbohydrate per kilogram body weight is advised for people practicing sports in a moderately intensive way (1 hour of exercise per day) and 6-10 grams of carbohydrates per kilogram body weight for intensively active athletes (1 to 3 hours of exercise per day) and up to 8-12 grams of carbohydrates per kilogram body weight for extremely active athletes (more than 4-5 hours per day). This is based on athletes for whom optimum availability of carbohydrates is important for the training intensity and performance (in particular elite athletes). People who seriously participate in sports but may not always train at such a high intensity can lower this quantity. (2) With respect to diets with a low energy intake (< 1,800- 2,000 kcal per day), the optimum ratio of energy intake between the macronutrients should be determined on an individual basis in accordance with exercise goals. (2)
For endurance athletes, and sports teams who sustain moderate to high activity levels over a longer time (> 40 minutes), it may be useful to optimise the muscle glycogen supply before performing strenuous exercise (for example a race or a match) to ensure optimal performance. This can be done by increasing the quantity of carbohydrates consumed for 2-3 days prior to the event. In order to avoid excessive energy intake, the increase in energy from carbohydrate can be offset by a reduction in fat intake. It is often advised to combine carbohydrate loading with a less heavy training schedule to spare glycogen stores. (3)
TABLE Guidelines for carbohydrate intake before exertion to optimise muscle glycogen supply
Carbohydrate during exercise
Carbohydrate intake during exercise can help spare muscle glycogen and allow exercise to continue for a longer time and/ or at a higher intensity. Research studies have determined the quantity and type of carbohydrate which can be taken during exercise for optimum performance (see table 5). For shorter duration exercise (up to 30-75 minutes) evidence suggests there is no need for replenishment of carbohydrate. A mouth rinse with small quantities of carbohydrate may be helpful. In the case of exercise lasting 1-2 hours a carbohydrate intake of 30 grams per hour is recommended and for exercise lasting 2-3 hours the recommendation is increased to 60 grams per hour. This can be one type of sugar (e.g. glucose) or a mixture (e.g. glucose and fructose, i.e. beet or cane sugar). For ultra-endurance exercise of a certain intensity level the quantity is even higher and it is recommended to use a mix of carbohydrates. This is because different sugar molecules use different transporters in the intestine and so the aim is to maximise absorption of each type of carbohydrate. Advice on carbohydrate intake depends on body weight and training status of the sportsperson. (2,4)
TABLE Guidelines for carbohydrate intake during exercise
Carbohydrate after exercise
After exercise performance carbohydrates are important for the replenishment of glycogen stores. When sufficient rest can be taken between exercise sessions a normal diet will replenish the glycogen stores within 24 hours. However, when fast recovery is required or when the glycogen supply is to be optimised, additional carbohydrates in both solid and liquid forms are preferable immediately after exercise and during the following 2–4 hours after exercise. The required quantity of carbohydrate depends on the duration, intensity and frequency of training and body mass. After a longer endurance training session the body needs more carbohydrates to replenish muscle stores than after a strength training session. To optimise glycogen replenishment 1.2 gram carbohydrate/kg/ hour is advised post-exercise. This can be decreased to 0.8 gram carbohydrate/kg/hour when consumed in combination with protein (0.2-0.4 gram protein/kg/hour). Here the frequency for the intake is every 15 to 30 minutes. (5)
Publication Sport & NutritionWhat does science say about the role of nutrition in sports performance?
- Public Health England (2015). Carbohydrates and Health Report. Scientific Advisory Committee on Nutrition. July 2015.
- American College of Sports Medicine, Academy of Nutrition and Dietetics and Dietitians of Canada. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Journal of the Academy of Nutrition and Dietetics, 2016; 116: 501-528.
- Loon van L.C.J. (2013). The human engine.
- Jeukendrup A. (2014). A Step Towards Personalized Sports Nutrition: Carbohydrate Intake During Exercise. Sports Medicine. 2014;44 (Suppl 1):S25–S33. doi 10.1007/s40279-014- 0148-z.
- Beelen et al 2015