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  • Writer's pictureAllison Koch, MS, RD, CSSD, LDN

Suffering From Stomach Issues Mid Run? Learn How To Train Your Gut

One of the most common conundrums runners face is stomach – or gastrointestinal (GI) – distress mid-run. It doesn’t happen to everyone – and is highly specific – but I have had way more complaints of inability to eat before, during, or after a run due to an upset tummy or fear of having to use the bathroom mid-run. Why does it happen? And is there anything you can do to combat it? The short answer: there is a multitude of reasons and yes. Let’s dive in a bit more.

First, why does it happen? Many different factors contribute to GI distress mid-run including the jostling of your internal organs as you run, the fact that blood is flowing to your muscles and shunted away from your gut during especially hard or long efforts, hormonal fluctuations, and the fact that running forces food through your digestive tract faster. Add to that race day nerves and you have the perfect storm of gut-wrenching issues that could impair your performance.

You probably know someone who seems like they can eat anything and never have any issues. Or you may know someone who is super sensitive. Stomach issues are very individualized but the majority of us at some time or another have suffered from them. And they can make or break your run whether it’s a workout, long run, or race.

If you are running less than an hour, you may be able to get away with minimal fuel pre or mid-run. But in order to optimize your workouts and long runs to achieve the much-desired training adaptations while avoiding the dreaded bonk, you need adequate fuel – preferably carbs – before, during, and after your workout. How then should you handle your sensitive gut? Just like you train your lungs, legs, and glutes, you need to also train your gut. Think about it—you would not wait until race day to practice race pace – why would you wait to execute your fueling strategy?

So how do you train your gut? The following tips and suggestions may help.

Experience Matters

One of the factors contributing to GI distress is the fact that blood is directed away from our intestines during exercise to provide oxygen to our muscles and digestion is deprioritized. The more you run, the more your body adapts. The same is true for pre and mid-run fueling. The more you practice it, the easier it becomes, and the more you can tolerate.

Identify Potential Food Sensitivities – Especially Pre-Run

Even if you do not have what is considered a full-blown food allergy or sensitivity, you probably know there are certain foods you just cannot tolerate before a long run or workout. For me, that’s most dairy foods, anything high in fat or fiber, and anything spicy or carbonated. Simple solution: avoid those before you run. For some that may mean just avoiding those foods in the pre-workout meal. For others, it may need to be a full 24 hours of abstaining from those foods. Figure out what works best for you and stick with it.

Unsure what may be causing you to run for the woods? Keep a journal and pay attention to what you are eating before, during, and after your workouts and how you feel. Trial and error and paying close attention to your diet can help you identify what does and does not work for you and you can then adjust accordingly.

Practice Your Fueling Strategy

This should not come as a surprise. If you have heard any of my presentations or Facebook chats, you know my motto: practice makes PRs. Regularly practicing your fueling strategy during training is the best way to minimize race day issues. Typically, I recommend 30-60 grams of carbohydrate per hour mid-long run (anything over 60 minutes). Seem like a lot? Elites can take up to 90-100 grams/hour. Why? They have trained their guts to be able to absorb this level of carbohydrate while performing at a very high level. 30-60 grams/hour is the equivalent of a minimum of 1-2 gels/hour plus a sports drink that contains both carbohydrates and electrolytes.

If you are not used to taking anything or that much, start with 30 grams/hour and slowly ramp it up until you are at a point where you are comfortable. I have also found that sipping a gel or slowly consuming gummies over a mile is easier on my stomach than taking it all at once. This makes sense, as when you gulp down your solid nutrition it is like putting a super-concentrated carbohydrate bomb into your stomach and it is hard to digest and absorb it all at once. For more on how to fuel pre, post, and during your long run, check out this article.

Experiment Now

There is a myriad of options available for fueling mid-run. Find one that works for you and stick with it. Unsure what works best? Experiment (not all at once though). Consider experimenting on a shorter, easier run versus a group long run in the event it does not agree with you. Be sure to take your mid-run fuel with water and not electrolyte or sports drink so as not to overload your gut with sugar and electrolytes all at once. Typically, I recommend alternating water and sports drink over the duration of a long run if possible. Finally, remember – you are not your running partner(s). What works for them may not work for you.

Don’t Forget About Hydration

Often GI distress can be related to over or under hydration and have nothing to do with what you ate pre or mid-run. Make sure you are staying on top of your hydration with tips found here.

Incorporate Other Gut-Promoting Habits

Running has numerous health benefits but it can also stress the gut in a major way. And it is not just what you eat before, during, or after that impacts how you feel mid-run. Make sure to include some gut health-promoting foods throughout your week to ensure your gut microbiome (basically the microorganisms found in our guts) is optimized. That means consuming probiotic (or good-for-your-gut bacteria) containing foods like yogurt, kefir, kombucha, kimchi, and sauerkraut as well as others. You can even find foods that have been fortified with probiotics like baking mixes, cereals, and snack bars.

You will also want to incorporate prebiotic containing foods to ensure the probiotics have adequate fuel. Prebiotics are a type of indigestible fiber found in many different fruits, veggies, and grains like garlic, onions, leeks, asparagus, bananas, artichokes, barley, oats, and apples. Making sure to include at least one pre and probiotic-containing food per day can be a great way to support your overall gut health.

What about a supplement? As with most nutrients, you are better off with a whole food source vs. taking it in a pill form. That being said, there are times when I will recommend a probiotic supplement. If you are considering one, feel free to reach out to discuss why and what to look for.

Tried all the above tips and still struggling with your gut health? As with anything nutrition related, it is very personal and if you are struggling with GI issues, be sure to reach out to me ( and we can discuss what may be contributing to or causing distress.

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