Now we have come to the blog that puts it all together and talks about the recommendations for carbohydrate intake during exercise. First it is essential to know what the goal of an exercise session or workout is before we can recommend carbohydrate amounts and types. If the goal is an optimal performance, the following recommendations are appropriate.

So far we have seen:

• Not all carbohydrates are equal, some are used more rapidly than others and those are the ones we need for optimal performance (Read more here)

• Carbohydrate intake even small amounts can improve performance during prolonged exercise (>2h) but more seems to be better (Read more here)

• Your body cannot use more than 60 g/h of a single carbohydrate (Read more here)

• This limitation can be overcome by using multiple transportable carbohydrates like maltodextrins and fructose or glucose and fructose (Read more here)

• Intakes of 90 g/h of glucose fructose can enhance performance during exercise >2.5h (Read more here)

• Carbohydrate intake and even a mouth rinse can improve performance during shorter, high intensity such as a 40km time trial (Read more here)

Based on this we have put together a chart that can help you to determine how much and what carbohydrates you need. To determine how much carbohydrate is recommended, we need to know the exercise duration.

Exercise <30min

If the exercise is less than 30 min there is no need to take in any carbohydrate. There is little or no evidence that carbohydrate intake or a mouth rinse does anything. It may not harm, but there does not seem to be a need.

Exercise 45-75 min

When the exercise is a little longer, say 45-75 min and it is “all-out” for that duration, performance will benefit from either carbohydrate intake or a carbohydrate mouth rinse. What is best depends on the practicalities of ingesting carbohydrate. Sometimes it is easier to simply rinse and sometimes it will be just as easy to swallow the carbohydrate solution. The types of carbohydrate does not seem to matter much here.

Prolonged exercise

For exercise lasting 1-2 hours, some carbohydrate has been shown to improve performance and 30 grams per hour is probably sufficient. With increasing duration, it is recommended to increase the intake up to 60 g/h and beyond 2.5h even up to 90 g/h. Especially as the exercise duration goes beyond 2h there appears to be a dose response relationship and higher intakes are recommended as long as this does not cause stomach problems (or other gastro-intestinal distress).

If the intake is not higher than 60 g/h any rapidly oxidized carbohydrate will work (glucose, sucrose, maltodextrins and some forms of starch). When the intake is higher than that, it is recommended to use carbohydrate mixes that use different transporters.

The recommendation chart

So to use the figure above, first establish the duration of your event. That will largely determine the amount of carbohydrate you need. The type of carbohydrate is then dictated by the recommended amount.

The advice in all cases is to practice whatever strategy you are planning to use in a race. Practice - practice - practice. Your gut will adapt and chances of gastro-intestinal discomfort will be reduced. This practicing is even more crucial at higher carbohydrate intakes.

Carb sources in products

Unfortunately manufacturers of sports drinks, gels and other carbohydrate products don’t always list the quantities or ratios of ingredients. So you may find on a label that a product contains a number of carbohydrates but it does not state the exact amounts of each of them. Very often fructose is used in small quantities to improve taste. But these amounts are too small to have any physiological effects. It is unlikely that you will find the ratio of carbohydrates in products that do not specifically mention a glucose:fructose or maltodextrin:fructose ration but the best way to find out may be to write to the manufacturer of the product.

Mix and match

Finally, it is important to know that you can mix and match your carbohydrate sources and use drinks, gels, chews and bars depending on you personal preferences. For any solid foods, make sure fat, fibre and protein intake are low, so these ingredients don’t slow down the delivery of carbohydrate and fluids.

Reference

1. Jeukendrup, A. E. Nutrition for endurance sports: marathon, triathlon, and road cycling." J Sports Sci 29 Suppl 1: S91-99, 2011.

2. Jeukendrup, A. (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise." Sports Med 44 Suppl 1: 25-33, 2014.