Complaints of bloating, cramping, nausea, and diarrhea are all too common for athletes, especially on race or game day. Your training cycle may be right on track, but if GI issues are holding you back from achieving your goals, you need to prioritize training your gut as well. A well-functioning GI system is key to delivering important nutrients to your body which can be impaired if you don’t identify what foods or beverages could be contributing to the problem.
What is gastric emptying?
Gastric emptying is the process where the food or beverage you consumed empties from your stomach into your small intestine to provide your working muscles the nutrients it needs to continue running.
During training the body can only store a limited amount of glycogen (stored carbs) in the liver and muscle to maintain energy. If you are exercising continuously longer than 90 minutes at a low-to-moderate intensity or 45 minutes at a higher intensity, glycogen stores may be significantly reduced resorting to using fat as your main fuel source. Unfortunately, fat is not as efficient as carbs, especially when the intensity picks up during a workout or race; therefore, fueling with carbs during endurance training is necessary to prevent “bonking” or “hitting the wall”.
During exercise, blood is shunted away from your gut to meet the demands of your working muscles rather than for digestion. This can result in delayed gastric emptying and GI issues when fueling with food during exercise. This is why gut issues are common in endurance athletes when training or competing in events longer than 2 hours.
Strategies to Training Your Gut
Taking in large volumes of food and fluid during training can lead to reduce gastric emptying and cause GI problems. To avoid these issues, you need to build a tolerance for food and fluid over time to be able to maintain high performance while reducing your risk of GI symptoms.
Dehydration can contribute to worsening gastric emptying. Losing more than 2% of your body weight in sweat during training can cause GI distress. To prevent this from happening, it’s suggested to start drinking small sips of fluid, about 3 to 4 sips every 15 minutes to allow your gut to adapt ingesting larger volumes over time. The recommended goal is to reach approximately 4 to 8 ounces every 15 minutes, depending on your sweat rate. Remember to start small so on race day your gut is able to handle the amount of fluid to prevent dehydration.
Choosing the Right Beverage
Fluid absorption starts in your gut, specifically your small intestine, which balances the amount of water and sodium so your blood has the right level of osmolality. Osmolality is defined as the concentration of dissolved particles in a solution, which can impact your hydration. Fluids you drink during endurance training should have a lower osmolality (hypotonic) than your blood. This can allow the fluid to be absorbed more quickly into your bloodstream. If your beverage has a higher osmolality (hypertonic), containing a greater concentration of carbs, this can slow gastric emptying, diluting the fluid in your gut rather than your bloodstream, leading to dehydration and GI distress.
Beverages containing both sodium and carbs actually work well together to increase fluid absorption into your cells. Without carbs, the flow of sodium and water in your bloodstream slow down. Pairing your fluids with both carbs and sodium can help prevent the fluid from sitting in your gut causing bloating to optimize absorption and hydration.
What beverages work best when you are training loner than 60-90 minutes? Choose hypotonic beverages with 3-4% carbohydrate solution (about 7-9 g carb per 8 ounces), 180-225 mg sodium, and 60-75 mg potassium per 8 ounces. Some good examples include, OSMO hydration, Skratch Labs, and Clif Shot (electrolyte drink).
Amount of Carbohydrate
Eating or drinking carbohydrates during endurance training can lead to GI issues if your gut is not used the type and amount of carb you are consuming. Your gut needs to slowly adapt to a new regime to reduce the risk of GI issues. That means instead of loading your gut with 30 grams of carb per hour, start with 15-20 grams of carb initially. There is not specific protocol of how long you should wait to increase the amount, but increasing the amount by 10-15 grams of carb over a few training weeks of training at varying intensities should give you an idea if that amount works. The goal is to fuel with 30-90 grams of carb per hour without causing GI issues, so if you reach 40 grams of carb per hour without gut problems and your energy levels are maintained throughout your training, then you found the right dose for race day. Remember you need to practice fueling not just on long easy workouts, but on shorter more intense training to best mimic race day nerves and intensity.
Type of Carbohydrate
The type of carb can also have an impact on your gut. Sugars are simple carbs which are digested somewhat similarly, but how they are absorbed and metabolized varies which can have an impact on your gut when exercising.
Differences between two sugars, glucose and fructose, vary greatly on how they are transported to your gut. Glucose uses a more active transport from your gut to your intestinal cells. Glucose can be absorbed up to 60 grams of carb per hour. Whereas fructose (fruit sugar) uses a more passive transport and can only absorb 30-40 grams of carb per hour. If you are using fructose alone as a fueling source, you may experience more GI issues compared to combining both glucose and fructose which can increase your absorptive capacity. Choosing fueling options with this combination is most relevant for more intense exercising lasting longer than 2 hours.
Testing out which type of carb, whether it’s from a gel, chew, liquid or bar is important to see what works best for you. Here are some basic tips to training your gut and making sure your fueling plan is set for race day!
· Choose a hypotonic beverage containing sodium and a small amount of carb to prevent dehydration and GI issues.
· Fuel with a small amount of carb, 15-20 grams per hour when first introducing food when training longer than 60 minutes. Gradually build to the amount that works best for you ranging from 30 to 60 grams of carb per hour.
· Consider using a carb choice containing a mix of glucose and fructose when training longer than 2 hours.
· Start training well-hydrated. Consider drinking 4 to 8 ounces of fluid every 15 minutes by taking small sips rather than drinking a large volume of fluid every hour.
· Only take energy gels or chews with water, never alone and never with a high carb sports drink. Ingesting an energy gel or chew without water can slow gastric emptying leading to GI upset. If you take an energy gel or chew with a high carb sports drink, this could lead to taking too much simple sugar at once.
· Avoid high fat or fiber-rich foods before training.
· Don’t try any need foods or beverages on race day!
Remember, you won’t be able to handle the amount of fluid and food that is recommended for optimal performance right from the start. You need to train your gut slowly to be able to reach the amount that works best for you without any GI distress. Your gut can adapt quickly, so track your fueling plan over your training cycle to know what works and what doesn’t so there are no surprises on race day.