Have you ever wondered if you should fuel your long workout with a “natural” food, like applesauce or bananas, rather than the “unnatural” gels? Gels often get a bad rap for being “unhealthy.” However, gels really are the best fuel source for in-race nutrition. Read on to find out more.

Intake of 90 grams of carbohydrate per hour of exercise has been shown to improve performance during exercise longer than 2.5 hours. That being said, taking in this amount of carbohydrates is absolutely useless unless it is actually absorbed, since our bodies can’t use these carbohydrates as an energy source unless it is absorbed. If these carbohydrates remain unabsorbed, it not only does not provide us with energy, but also causes gastro-intestinal discomfort that could sabotage your performance.

To actually absorb the 90 grams of carbohydrates each hour, we must use multiple transporters in the gut. To fully understand this, you first need to know that not all carbohydrates are created equal and some are more rapidly used than others. The simplest form of carbohydrates are monosaccharides. Monosaccharides are bound together in differing combinations, sequences and lengths to make all the different kinds of carbohydrates. All carbohydrates are eventually broken down into monosaccharides, which are then absorbed in the gut. There are three types of monosaccharides:

  1. Glucose
  2. Fructose
  3. Galactose

This diagram shows monosaccharide absorption from the small intestine (AKA the gut) into the blood. As you can see, different transporters are used for glucose and fructose absorption.

Our gut has different transporters for each monosaccharide. As a result, we absorb the different monosaccharides at different rates. As well, these transporters can become saturated. This means that they can only transport a certain amount of monosaccharides. Once we exceed this saturation threshold, the transporters can no longer absorb the monosaccharides.

Your body cannot absorb more than 60 grams per hour of a single carbohydrate. However, as I mentioned above, research has shown consuming 90 grams per hour improves performance. To overcome this absorption issue, we must consume mixtures of carbohydrates during exercise so that multiple gut transporters are used. To best use our transporters, we should aim to consume a ratio of 2 glucose per every 1 fructose. Galactose isn’t found naturally as a monosaccharide in nature, and is absorbed rather slowly. Because of this it isn’t recommended as a fuel source during exercise.

My favourite gels- Clif vanilla.

It’s this ratio of glucose to fructose that makes gels the most ideal in-race fuel. Most gels are created specifically with our gut transporters in mind, so they contain the right ratio of glucose to fructose for ideal absorption. Unfortunately, food products do not need to list the exact quantities of ingredients, but the ingredients list can provide some good insight. For instance, if you look at the ingredients label on a GU roctane gel, the first ingredient is maltodextrin, which is glucose molecules bound together, followed by water, then fructose. Ingredients are listed by weight, so this indicates that of the carbohydrates present in this gel, there is more coming from glucose than fructose.

On the other hand, most “natural” foods don’t contain this glucose to fructose ratio. As a result, they can’t be consumed at a rate of 90 grams each hour and actually be absorbed. For instance, honey contains more fructose than glucose per serving and bananas contain equal amounts of glucose and fructose.

Most athletes don’t consume enough carbohydrates during exercise. As a result, this 2:1 ratio of glucose to fructose doesn’t matter. If you plan on taking in carbohydrates from only one type, then do not go over the 60 grams per hour. In addition, if you are exercising for less than 2.5 hours, then 60 grams per hour is sufficient.

Practice, practice, practice!

As mentioned in past blogs, you should be training your gut to absorb carbohydrates. With fall races just around the corner, now is the time to start practicing! I cannot stress enough the importance of practicing your race day nutrition plan. Your gut will adapt and gastro-intestinal discomfort will be reduced. Checkout this past blog on the importance of training your gut for race day success.

Want to stay updated with the latest nutrition tips and resources? Check out my Facebook page: Megan Kuikman Registered Dietitian and follow me on instagram @the.running.dietitian