Runner’s Stomach: What Causes It and How to Get Rid of It

Have you ever hit the ground running, only to be sidelined by lower abdominal pain and nausea soon after? You're not alone. A runner's stomach, a common digestive issue experienced, can dampen your workout routine.

Imagine the frustration of training hard, only to have the pelvic floor muscles betray you mid-run. It can disrupt your training schedule, cause discomfort, and leave you feeling discouraged.

But you can prevent it. By understanding it and taking some simple steps, you can keep your digestive system happy and your runs on track. Let's explore the causes and discover how to avoid it.

» Prevent stomach pain after running with dietary recommendations

What is a runner's stomach?

Runner’s stomach refers to exercise-induced gastrointestinal (GI) distress symptoms such as cramping, nausea, diarrhea, and vomiting. It can happen during or after a workout and generally doesn't last linger than 24 hours

It likely earned its name because it was prevalent in people who ran long-distances during marathons—an estimated 30–90%. [1,2] Younger people are most affected by this unpleasant condition.

» Read our beginners guide on becoming a runner

What do experts say?

Holley Samuel MEd, RDN, CPT, owner of Holley Fueled Nutrition, says that many of her clients report “Stomach pain with an urgency to have a bowel movement. She also mentions that they "Feel they can’t take in any hydration or fuel, before, during, or after a run."

On the other hand, Stevie Lyn Smith, a board-certified sports dietitian, says, "There’s no discernable difference when it comes to biological sex and GI distress.” She also adds, “I, unintentionally, tend to work with more females than males in my practice, but I hear complaints of lower abdominal pain across the board.

» Explore meal options before a workout to fuel your performance

Running isn’t the only type of exercise that can lead to these digestive symptoms, but it is the most documented. Some research suggests that team-based sports, high-intensity anaerobic drills, and sprinting can all trigger runner's gut. But, only small experimental studies have attempted to investigate these relationships. [3]

5 reasons why you get stomach cramps when running

1. The way the gastrointestinal tract absorbs and regulates water and electrolytes changes. It can prioritize maintaining hydration throughout the body, which can impact digestion.
2. Exercise stimulates the release of various gut hormones like ghrelin and leptin that influence digestion and energy availability. [4,5] While these hormonal changes are crucial for performance, they can sometimes lead to GI distress.
3. The body strategically reroutes blood flow. Exercising muscles receive a bigger supply to meet their oxygen and nutrient demands, while the gastrointestinal tract gets less. This temporary reduction can contribute to delayed gastric emptying.
4. Gastric emptying, the process by which food moves from the stomach to the small intestine, slows down during exercise.
5. Exercise can weaken the lower esophageal sphincter, a valve that prevents reflux, potentially leading to heartburn if food intake during exercise isn't managed well. [1,2]

» Check out how to make the most out of your post-workout meal

Does high running impact make a difference?

Runner's stomach is more common during high-intensity exercise. But, the exact reasons some people experience gut issues while exercising and others aren't an area of active research. [1]

» Check out the best exercises for heart health

The high impact of running on the body physically jostles an already extended torso, which can lead to abdominal pain and stomach aches—specifically lower GI distress like bloating and diarrhea. [1,2]

On the other hand, activities like cycling are a lower-impact endurance-based workout, and the position of the body is more often associated with upper-GI distress such as acid reflux. [2,6]

» Find out everything you need to know about your running heart rate



There's no one-size-fits-all solution. While working with a dietitian or running coach can help personalize a plan, there are steps you can take to improve your gut health and optimize it for absorbing and processing pre-workout and recovery fuel. This can significantly reduce the risk of digestive issues.

InsideTracker’s gut health goal—compatible with the Ultimate+Subscription plan—offers a personalized approach to optimizing your gut microbiome. It uses data from blood tests and wearable sleep trackers to create recommendations for foods, supplements, and stress management techniques that are linked to improved gastrointestinal function.

» Discover the crucial effect of creatine kinase and cortisol on stress

Here's how it works

InsideTracker analyzes key biomarkers, like hsCRP, a blood marker for inflammation. Research shows a two-way relationship between hsCRP and gut health. Elevated hsCRP levels may indicate poor gut health.

» Find out how to measure inflammation

Based on your individual biomarker profile, InsideTracker prioritizes personalized recommendations in your action plan. For instance, you might be advised to incorporate fermented foods into your diet to improve specific gut health markers.

By getting a blood test every three to six months, you can track your progress and adjust your approach based on your body's current needs. This process lets you to continually optimize your gut health and minimize your risk of runner's stomach.

How nutrition impacts runner's stomach

Proper nutrition plays can prevent runner's stomach, the unpleasant gastrointestinal (GI) symptoms experienced by many runners. By strategically planning your meals and fueling the body appropriately, you can significantly reduce your risk of digestive distress and optimize running performance.

» FInd out how beetroot juice improves performance

Timing your meals

The timing of your meals plays a crucial role in preventing runner's stomach. Certain foods, particularly when eaten too close to the start of exercise, can increase the likelihood of experiencing digestive issues.

Another common mistake is poor timing of nutrition. Taking a concentrated carbohydrate gel with a sugary sports drink can be overwhelming for some runners' digestive systems. Similarly, taking them without water can also lead to discomfort, as most gels and chews are designed to be consumed with fluids while running.

» Dispel common myths about carb loading

While high-carbohydrate gels and drinks provide runners with a quick energy boost, it's important to be mindful of sugar content. Too much sugar too quickly can draw excess water into the gut and potentially lead to diarrhea. [1] This applies not just to sports beverages, but also to sugary snacks you might consider pre-run.

» Discover more about how to fuel to go the distance

What about underfueling?

Many runners, especially those new to pre-run fueling, struggle to eat before a run. Stevie highlights this point. Holly says "I hear from about 75% of my clients when we start working together that they can't tolerate or can only do so with small amounts of fuel before a run."

» Explore the best foods to slow aging

If you find it difficult to eat solid food before a run, consider a carbohydrate-rich sports drink as a readily absorbed source of energy. Other good pre-run options include:

• 1–2 graham cracker rectangles
• 1 applesauce packet
• 1 gel or 1 serving of sports nutrition chews
• 1 banana (or ½ the banana to start)
• 2–3 dates
• 1–2 servings of dry cereal
• 1 small cereal or granola bar (or ½ the bar to start)
• 1 serving gummy candy
• English muffin with jelly

Runners who don't meet their daily energy needs, often recommended to be higher than the average person due to their activity level, are more prone to runner's stomach. Those new to taking in fluids and food during exercise are twice as likely to develop GI symptoms compared with runners who regularly consume carbohydrates mid-run. [1]

Dehydration

While dehydration is not a direct cause of runner's stomach, it can significantly worsen existing symptoms. [1] Therefore, prioritizing adequate hydration throughout the day and during runs is essential for preventing gastrointestinal distress.

» Find out how protein helps with workout recovery

Sports drinks can be helpful for runners by providing electrolytes, carbohydrates, and fluids, but only for those who tolerate them well. The extra nutrients can aid digestion and performance. However, be cautious of sugar content – too much too fast can cause gut issues bloating and diarrhea.

Supplements

Some supplements may also trigger digestive distress for individuals. Caffeine, a commonly ingested stimulant and performance enhancer, is associated with nausea during exercise. In addition, cyclists in a small study cited gut discomfort and higher perceived pain after supplementing with exogenous ketones. [7]

Other supplements including iron or magnesium also have reported GI side effects. While they are beneficial in maintaining overall health and performance for some, it may take the digestive tract time to adjust.



How to relieve stomach pain after exercise

The best long term solution is to optimize your nutrition fueling.

In a similar way to building your running mileage, the digestive system needs to be trained to handle fuel and hydration while exercising. Practice strategic pre-run fueling, proper timing of in-run nutrition, and gradually training the gut to tolerate food and fluids during exercise.

Start small with easily digestible carbohydrates—low in fiber—20–40 minutes before a morning run. A serving size could be around 15–20 grams of carbohydrates, which is roughly half of a large banana. As your gut adjusts, you can gradually increase the amount you take pre-run.

For workouts that don't happen right after waking up, Holley suggests reducing fiber and fat content in the previous meal—lunch or dinner—and incorporating a small carbohydrate-rich snack 30–60 minutes before your run.

Silence your runner's belly rumbles

Runner's stomach can significantly impact your performance. While the exact causes vary, a combination of factors like reduced blood flow to the digestive system, hormonal changes, and food choices can contribute to these unpleasant symptoms.

The good news is that it's largely preventable. By strategically planning your meals, staying hydrated, and experimenting with different pre-run fueling options, you can train your gut to reduce your risk of digestive issues.

To address runner's stomach, InsideTracker offers a gut health goal specifically aimed at improving the microbiome. Based on the analysis of your blood biomarkers, you'll get personalized and science-backed recommendations to optimize your health and live healthier and longer.

» Silence your stomach aches by working on your diet with Insidetracker