Proper carbohydrate replenishment is one of the cornerstones of athletic performance. Endurance sports require the body to have a continuous source of energy to maintain a high pace for extended periods. However, not all carbohydrate sources are absorbed in the same way, and understanding the best combinations can make the difference between achieving peak performance or entering the dreaded fatigue zone and a significant drop in performance.
Why do we need carbohydrates in endurance running?
During prolonged exercise, glycogen reserves (the body's storage form of carbohydrates) are gradually depleted, which can lead to fatigue and decreased performance. To prevent this, continuous carbohydrate consumption during activity ensures the necessary fuel to maintain the intensity of the effort.
The general recommendation for carbohydrate intake during endurance exercise is at least 30 to 60 grams per hour for activities lasting between 1 and 2.5 hours, and 90 to 120 grams per hour for longer activities. However, the challenge lies in the limited capacity for carbohydrate absorption, especially when it comes to a single source like glucose.
Glucose vs. Fructose: The Role of Different Types of Carbohydrates
Glucose is the main carbohydrate used by the body during exercise. It is rapidly absorbed in the intestine and transported to the muscles to be used as energy. However, there is a limit to the amount of glucose that can be absorbed per hour, around 60 grams, due to the saturation of glucose transporters in the intestine.
To overcome this limitation, scientists discovered that combining glucose with fructose (another type of carbohydrate) can increase the overall capacity for carbohydrate absorption. This happens because glucose and fructose use different transporters in the intestine to be absorbed—glucose uses the SGLT1 transporter, while fructose uses the GLUT5 transporter. Therefore, combining the two types of carbohydrates allows more carbohydrates to be absorbed at the same time, increasing the efficiency of energy replenishment.
The 1.0:0.8 ratio of glucose to fructose.
Recent studies have shown that a glucose-to-fructose ratio of 1.0:0.8 is quite efficient, meaning that for every 1 gram of glucose, 0.8 grams of fructose should be consumed. This combination optimizes carbohydrate absorption, allowing the body to utilize up to 120 grams per hour, significantly increasing energy replenishment capacity.
This ratio has two major advantages:
- Greater carbohydrate absorption per hour: By using different absorption pathways, this combination allows for increased carbohydrate intake beyond the limits of using glucose alone.
- Reducing gastrointestinal discomfort: A common problem in endurance activities is gastrointestinal discomfort caused by a high intake of carbohydrates. Glucose alone can overload the digestive system, but the addition of fructose reduces this risk, as it uses a different pathway to be absorbed.
Practical Strategies for Endurance
For those who practice endurance sports, the carbohydrate intake strategy should be adapted to the duration and intensity of the exercise. In long-duration activities (over 2.5 hours), it is advisable to start replenishment in the first few hours after exercise, using supplements with a glucose to fructose ratio of 1.0:0.8.
Remember to test your nutritional strategy during training to ensure your body adapts well and to avoid surprises during the race. Each athlete responds differently to supplementation, so adjust the amounts according to your body and performance.
Conclusion
The science of carbohydrate supplementation has evolved significantly, and understanding the correct glucose-to-fructose ratio is fundamental to optimizing performance in endurance sports. The 1.0:0.8 ratio allows for greater carbohydrate absorption per hour, ensuring continuous energy for prolonged activities while reducing the risk of gastrointestinal discomfort. Therefore, when choosing your carbohydrate supplements, pay attention to the composition and maximize your performance!
