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How To Avoid Gl Distress/ Stomach Issues During An Ultramarathon


Studies have suggested that over 90% of ultra-runners experience at least one gastrointestinal-related symptom during an ultramarathon race. GI issues is often the most common issue for ultra-runners to DNF in ultramarathons. Ultra-runners can learn how to minimize the chances of experiencing common symptoms of GI distress and recommendations to overcome such issues during an ultramarathon.


Common Stomach Issues in Ultramarathons


During ultramarathons, common gastrointestinal (GI) problems include nausea, bloating, heartburn, diarrhea, and vomiting.


Why Are Stomach Issues So Common in Ultramarathons?

Stomach issues frequently happen during endurance exercise because blood is diverted from the stomach to working muscles during activity, which will slow down and maybe even block digestion. GI distress is especially prevalent in ultramarathons because ultra-runners need to eat a significant amount to prevent glycogen depletion. High carbohydrate intake is necessary to prevent glycogen depletion and is associated with a higher rate of race completion. However, high carbohydrate intake can also cause GI distress, if the type of carb fueling is not tolerated by our body type.


How Ultra-Runners Can Prevent Stomach Issues From Occurring During Ultramarathons


Prevention is always the best plan. We should do everything in our power to prevent gut issues from arising in the first place. If GI happens, we should know how to overcome them.


1. Train Your Gut


Training our gut is probably the most important thing an ultra-runner should do before race day to avoid GI problems. We should try to incorporate as many calories in training as our plan to consume on race day. For example, if our goal is to take in 300 kcal/hr during our ultramarathon, we should be doing some long runs incorporating 300 kcal/hr.


Also, we need to train our gut for the specific types of foods, gels, drinks, or whatever we plan to consume on race day. Training the gut is critical for avoiding nutrition-related issues on race day. Additionally, doing so can increase the amount our stomach can tolerate, allowing us to better fuel our performance.


2. Nothing New On Race Day


If we’ve never eaten a type of food during a training session, then it’s not a good idea to eat one during an ultramarathon. We should test with a variety of different fuels in training and find out what works for us. 50km into a 100km ultramarathon is not healthy for our stomach to try something new. Because our stomach does well with a particular food when sitting at the kitchen table doesn’t mean it will react the same when we’re running long distance.


3. Eat Breakfast 2-3 Hours Before Exercises


It’s important to eat breakfast before an ultramarathon to prevent stomach issues. Going in fasted will increase the likelihood of nausea. It’s also essential to eat the right foods for breakfast and at the appropriate time. Protein and fat can take over twice as long to digest compared to easy-to-digest carbohydrates. Eating too close to the race start, doesn’t provide enough time for digestion, which can also lead to GI issues.

Before a race, we should eat a breakfast we have eaten before multiple training runs.


4. Have a Plan


We should know what we are going to use as energy and how much we will use. We should have a good fueling plan, that is part of ultra-running. We need to determine how many kcal/hr we plan to consume and where those calories are coming from. We need to create a backup plan to support issues like palate fatigue or GI issues.


5. Stick to Simple Carbs and Easy to Digest Sources of Fuel


Simple carbs are master in endurance sports, and ultramarathons are no exception. Things like carbohydrate drinks, gels, chews, and other simple sugars form the foundation of most of the energy ultra-runners take in. The simpler the food, the easier it is to digest. Multiple transportable carbohydrate solutions contain various forms of sugars and have shown superiority to isolated sugars.


6. Stay Hydrated, Maintain Electrolyte Balance, and Stay as Cool as Possible in the Heat


Not enough water, insufficient electrolyte and salt intake, and overheating can all cause our stomach to destroy us on race day.


  • Know how much liquid and electrolytes you need to take in based on the heat index and your individual sweat rate (have a plan).

  • Cool off at aid stations with cold towels, throw some ice in a buff or arm sleeves, and drink something cold.


7. Avoid NSAIDs


NSAIDs (like Ibuprofen) should never be taken during an ultramarathon. The science is clear, NSAIDs are dangerous during endurance activity. They don’t improve our performance, and they can affect our stomach. We should not consume NSAIDs medications during races.


8. Improve Gut Bacteria with Probiotics


A healthy gut microbiome decreases an ultra-runners tendency towards GI distress. Specific strains of probiotics have been shown to provide benefits including Lactobacillus and Bifidobacterium versions. A study showed that 4 weeks of supplementation with the previously mentioned strains lowered the incidence of GI symptoms in marathon runners. Limiting the consumption of saturated fat can also positively influence the gut microbiome.


Overcoming Stomach Issues During an Ultramarathon


If we get some stomach issues during an ultramarathon, we shouldn’t panic. All is not lost, and there are usually ways to overcome whatever symptoms we may be experiencing.


9. Slow Down


Nobody wants to slow down during a race. But more often than not, a modest drop in pace will help resolve common gastrointestinal distress symptoms.

Lowering our intensity allows more blood to redirect to the stomach, helping digestion. A small sacrifice in pace isn’t going to break us, but feeling super negative and lying down on the trail during a race will affect and shut down our brain and body. We should focus on the nice nature and kilometres.


If we find ourself with stomach problems in the last 10% of a race, we should activate our brain and body, push and press forward at a higher intensity to finish a good race.


10. Switch to Liquid Fuel


Switching to 100% liquid sources of fuel can be beneficial for ultra-runners experiencing GI distress. Liquids are easily digested and easier to get down when our stomach isn’t feeling well. The best liquid fuel sources are “multiple transportable carbohydrate solutions.” They contain multiple forms of carbohydrates (glucose, fructose, maltodextrin, etc.), increasing absorption and decreasing the odds of gut discomfort compared to single carbohydrate solutions.


11. Keep Drinking


We should remember that staying hydrated during ultramarathons is one of the keys to prevent stomach issues in the first place. When problems increase, it is critical to keep hydrating (water and electrolytes). Sometimes, when a runner’s stomach is uncomfortable, the instinct is to not take in anything. Consuming liquid doesn’t even sound good in extreme cases of GI distress. However, we must continue to hydrate, otherwise, we will cause some serious issues.

If we absolutely cannot keep anything down, it’s time to slow the pace significantly and even stop and rest if necessary until we can, so we can keep going later and finish the race.


12. Reduce Intake With GI Issues


When the symptoms of nausea and/or bloating come on during an ultramarathon, it’s probably time to slow down, and decrease our calorie intake. There is no exact number of calories we should reduce, as this depends on our body and the situation.


A good place to start might be to drop by 100 calories in the first hour and see if that provides relief. If not, an additional 50 might be efficient in the next hour and another in the next. So recommendation:


Planned kcal/hr – 350 kcal/hr


  • 1st hour after symptoms – 250 kcal

  • 2nd hour – 200 kcal

  • 3rd hour – 150 kcal

When symptoms diminish, increasing intake is recommended.


13. Be Persistent With Intake


Not only should an ultra-runner be persistent with hydration, but they should also be persistent in acquiring at least some energy. In longer ultramarathons, a consistent intake of less than 200 kcal/hour is not recommended. Not consuming enough fueling will likely make it worse.


14. Replace Some Carbohydrates With Fat


Converting fat to energy isn’t as efficient as converting carbohydrates to energy. However, replacing some carbs with fat may positively affect our stomach during times of GI distress. Taking in some fat in place of carbohydrates is far better than not taking in anything at all. Avocado or nut butter are good healthy fat. Remember to try these foods in training sessions before incorporating them into an ultramarathon.


15. Ginger


Ginger is a fantastic herb when it comes to helping alleviate nausea. If we are an ultra-runner, we have likely seen ginger at ultramarathon aid stations in the past. Keeping some form of ginger in drop-bags and with our support crew or our running pack is a good idea. Evidence suggests 1500 mg of ginger is effective for nausea relief.


Preventing and Overcoming Stomach Issues During an Ultramarathon


Nausea, bloating, indigestion, and other common gastrointestinal problems cause issues on endurance athletes and optimal performance. This is especially true in ultramarathons. However, we can significantly reduce the odds that stomach issues will ruin our big day with some planning and practice.



Support a Healthy Gut, Good Digestion, Focus On Pre-Race and Race Best Easy To Digest High Energy Foods and Feeling, And Enjoy A Super Ultramarathon!