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Cross Training For Runners

Runner’s Stomach: The Causes & How To Prevent It

11 Mins read

Would you like to learn how to manage and prevent GI distress during and after running?

You’ve come to the right place.

Call it “runner’s trots,” “the runs,” or “workout stomach.”

If you run hard and/or long, chances, at some point, you’ve had to high-tail to the nearest secluded tree or bathroom to relieve yourself ASAP.

Runners’ stomach symptoms can vary in frequency and intensity, including stomach cramps, diarrhea, nausea, vomiting, or bloody stools.

In this article, I’ll share the full guide to runners’ gut. More specifically, I’ll cover the following:

  • What is a runner’s stomach?
  • How running can cause an upset stomach
  • Mechanical causes of runners’ diarrhea
  • Measures for fewer stomach issues while running
  • And so much more.

Sounds great?

Let’s get started.

GI Distress When Running Is A Very Common Problem

If you are a runner suffering from GI issues, please know you are not alone.

Research has shown that this is quite a common problem for runners, with the majority of pavement pounders reporting experiencing varying degrees of GI distress either during or following a run.

According to a 2009 study conducted by the academic journal of Current Opinions in Clinical Nutrition and Metabolic Care, roughly 50 percent of runners experience GI distress problems—especially diarrhea and abdominal cramping—during hard runs, mainly long runs (we will see why in a moment).

Research has also found that athletes are twice as likely to experience GI distress issues during running than other endurance sports, like swimming or cycling.

What’s more?

The condition frequency is 1.5 to 3 times higher in elite athletes than the recreational runner, according to another study published in the September 2009 issue of the Lippincott William and Wilkins Journal.

What is GI Distress

Gastrointestinal distress, or gastric distress, is a general medical term used to refer to various symptoms. These include abdominal cramping, gas, burping, irritable bowel syndrome, indigestion or dyspepsia, vomiting, heartburn, constipation, nausea, diarrhea, and in some extreme cases, gastrointestinal bleeding.

According to research, these intestinal issues are one of the most reported reasons why so many runners drop out or don’t do as well as expected in a long race—especially during half-marathon and marathons.

In short, GI distress sucks.

Big time.

And can suck the fun out of your runs in no time.

And it’s quite prevalent.

Don’t take my word for it. Research has reported that runner’s stomach impacts around 30 to 90 percent of long-distance runners. It’s also more commonly reported in younger runners.

Why My Stomach Gets Upset From Running?

Here’s the truth. Running is a high-impact sport that not only takes a toll on your muscles and joints but on your digestive system as well.

This mechanical pressure forces the food and other waste to move through your GI tract faster when running. Also, blood flow is sent from your intestines to the working muscles, limiting their functionality.

This makes virtually all runners prone to stomach issues, but remember, it’s not a death sentence. You can do plenty of things to soothe or even prevent this condition by managing other factors such as your water intake, diet, running intensity, and even nerves.

Don’t get me wrong. No silver bullet will cure all of your stomach ills, but the following measures should help manage runners’ trots more efficiently.

And no one is immune—male or female—we all are prone. The longer we run, the more likely to experience runners stomach.

The main culprit behind the symptoms isn’t completely understood or found. But a few variables may increase the risk of discomfort—all of which you need to pay attention to if you’re prone to stomach issues.

Some of these variables include

  • Eating a meal within two to three hours before a run
  • Consuming sugary fruit juices before a run
  • Being dehydrated

Can you treat or prevent Runners Stomach while running?

Although it’s not the worst running-induced condition, dealing with gastrointestinal distress can turn your runs into a miserable experience.

Chronic runner’s stomachs may even force some runners to scale down on their training or quit the sport altogether.

Before I jump into what to do to prevent this condition, it’s key to under high GI issues can be problematic in runners.

How Does GI Distress Happen When Running

When you hit the pavement, your body’s primary focus becomes supplying (and delivering) the maximum amount of oxygenated blood to the working muscles. At the same time, blood is diverted from the stomach and intestines as your fatiguing body puts digestion on the back burner.

What’s more?

The mechanical bouncing linked with running is suspected of being a culprit in the relatively high occurrence of GI distress problems among runners—especially when compared to low-impact sports like swimming or cycling.

According to this theory, running nudges your digestive tract and forces the jostling of the lower intestines, which can irritate the GI tract, leading to gastric distress issues.

Causes of GI Distress During A Run

GI distress can be blamed on an array of different causes and conditions.

It can be due to several diverse factors, which can be divided into internal and external causes, and typically it is a mix of these factors that sets the stage for GI distress.

The most common external causes include nutrition (eating a heavy meal too soon to run or eating something that disagrees with you) and dehydration.

On the other hand, the most common internal causes include decreased blood flow to the digestive tract, mechanical stress, emotional problems, and existing gastrointestinal conditions, such as having a virus or stomach bug, ulcers, and other stomach ailments.

Additional resource –  Prevent Sunburn in runners

Physiological Changes From Running

Runner’s gut symptoms might be blamed on changes that happen during running. Running, in particular, can impact;

  • The levels of circulating gut hormones
  • Blood circulation to the digestive system
  • The rate of gut absorption
  • The movement of liquid and electrolytes between the digestive tract and tissues
  • Weakening of the lower esophageal sphincter tone or which can cause gastric reflux
  • Slowed movement of food from the stomach to the intestines
  • And so much more

The Impact of Food On Runners Stomach

Some foods, especially when consumed close to a run, can up the risk of expediting GI symptoms.

Consuming these foods can contribute to GI symptoms while running because they take a long to digest.


Poor timing

Overall, and often regardless of what you eat, having food too close to a run can lead to stomach issues.

What’s more?

Consuming gels without enough water may also trigger GI issues since most of these “fuel snacks” are designed to be taken with water. These concentrated forms of energy may provide you with the much-needed fuel, but too much sugar too fast can lure more water into your gut which can cause diarrhea.


Though dehydration doesn’t inherently correlated to GI issues, not drinking enough fluid during a run may exacerbate symptoms that you are already experiencing.


Some supplements may also contribute to stomach distress in runners. For example, caffeine, often used as a stimulant and performance booster, is linked with nausea during exercise.

Drugs & the Digestive Tract

Medication may also contribute to GI issues. For example, did you know that OTC anti-inflammatory drugs, such as ibuprofen, can increase your risk of GI issues five-fold?

Abuse them while you’re dehydrated—not unheard of while running—then you risk kidney failure. And you don’t want that.

How to Prevent Runner Trots When Running

The bad news is that there is no bulletproof way to avoid GI distress.

Why? It’s quite simple.

Because we are all so different and respond differently to different foods and meals.

No suit fits all.

Even so, there is no cause to worry.

The good news is there are several concrete things you can do to steer clear of GI distress.

Here is how I manage my GI problems, and some of this can help you as well—especially the first strategy.

Avoid Dehydration

Proper hydration is your first defense against stomach pain and pit stops.

We all know that dehydration can spell disaster for running performance and enjoyment. But it can also lead to, or increase the risks, of GI distress while running.

About 80 percent of runners who experienced 4 percent of body fluid losses or greater also reported experiencing GI distress problems, according to a study.

According to this study, slower gastric emptying, dehydration, and heat exposure (especially during the summer) can increase GI distress problems in runners.

Not only that, heat can make GI distress problems worse.

When it’s hot, your body demands more blood to be diverted to the skin to avert overheating. That’s one more reason to stay well-hydrated during running.

The old recommendation of downing plenty of water before a run is not enough. You need to stay well hydrated throughout the day.

And keep drinking the whole day so you won’t need to force yourself to drink before heading out the door.

Plus, make sure to drink plenty of water the moment you wake up in the morning.

After 7 or 8 hours of sleep, you will be dehydrated—even if you don’t feel thirsty—especially if you’re running in the morning.

Running for longer than 45 minutes? Take a water bottle and practice the “one gulp every mile” tactic, even if you don’t feel thirsty.

Additional resource – Prevent Acid Reflux In Runners

Go Easy With the Mileage

As I stated earlier, you will likely experience GI problems during long and hard training sessions.

This is probably due to dehydration, elevated body temperature, the great blood supply to the working muscles, and mechanical oscillation during hard runs.

In other words, runners are prone to GI distress simply because of the hard-impact nature of the sport. There’s no way around that.

The good news is that the gastrointestinal system, like the cardiovascular system, can adapt to training for most runners.

In other words, you can train your stomach like your muscles and cardio system to get good at running.

So what should you do?

Simple.  By experimenting with different foods and drinks, take your time “training” your stomach to properly handle the food.

What’s more?

For more accuracy, keep a food journal in which you keep track of the foods and drinks you ingest and their impact on your GI tract.

And be sure to experiment with different eating plans, and one day, BOOM, you’ll have the winning formula.

Give It Time

It takes time for your digestive system to do its job, so you shouldn’t rush it.  Instead, give your stomach enough time to break down and absorb a meal, especially after a heavy meal.

Aim for at least two to three hours between a meal and a run.

Can’t wait? Have a pre-run snack an hour before running.

Ensure it’s light and relatively easy to digest; it shouldn’t leave you feeling too filled or puffy.

What’s more?

Make sure to have an experimentative spirit. This will help you find what works the best over the long haul—and that’s what matters.

Keep your Diet Simple

This is as simple as it can get.

If you consume a meal (or drink) high in fiber, fat, protein, or concentrated sugars too soon before a run, expect GI distress.

There is no way around it.

Study after study has linked meals high in fiber, and fats with GI distress issues, not only in runners but in ordinary folks from all backgrounds and activity levels.

The trick here is to simplify your diet—especially during hard training days.

I urge you to do this if you have a bad history of GI problems or when running in the summer.

To stay on the right side, here are the key traits of a simple pre-run meal:

  • Reasonable in volume,
  • low-fiber,
  • low-fat,
  • has some protein,
  • and isn’t heavy in sugar.

For more ideas on proper pre-run meals, click here.

Running a marathon or a long endurance event? Then try sports drinks to meet your energy needs.

These are designed to provide your body with enough fuel to run strong.

But there’s a little caveat. Research has found that sports drinks with more than 10 percent of carbs concentration may trigger nausea, cramps, and diarrhea.

So to stay on the safe side, aim for products at or below 5 percent carbs concentration to clear up GI issues.

Pay attention to what you’re putting in your body the few hours before a run, or the day before a long run or big race. Overall, you should avoid acidic food or reduce your intake of milk, eggs, glutinous grains, nuts, and tomatoes.

Acidic drinks such as alcohol and strong coffee should also be avoided.

Some of the best low-acidic foods for runners include;

  • Bananas
  • Kale
  • Spinach
  • Soy such as soy beans, miso, tempeh, and tofu
  • Lentils and beans
  • Some whole grains, such as quinoa, millet, and amaranth
  • Fats like avocados, nuts, seeds, and olive oil
  • Milk
  • Yogurt
  • Herbal teas

Avoid Caffeine

According to a study, caffeine increases performance and can give you a quick energy boost.

But for some people, I included, caffeine sometimes leads to stomach problems.

Caffeine might provide you with the wrong type of boost.

Here is why.

Caffeine is a stimulant that can cause peristalsis—the automatic contraction of two muscles in the gut walls that gets the food moving through the digestive tract.

If your usual cup of joe triggers this peristalsis, then, by all means, avoid it before a run.

Drink water instead.

It’s good for you.

If you are still hung up on the coffee, have it before the run, giving your digestive system enough time to absorb the caffeine.

Additional resource – How to manage heart murmurs

Run Around Bathrooms

Planning routes that include bathrooms at various points for the GI issue-prone runner is an extremely helpful strategy.

Knowing that you have a place to go to for answering Mother’s Nature calls is comforting and can ease up the whole deal on you.

And also be prepared for emergencies.

Carry wet wipes or toilet paper in your pocket in case disaster hits during the most unexpected moment.

Also, try an over-the-counter (OTC) anti-diarrhea medication, such as Imodium—especially if you aver a bad history of “the runs.” But please, don’t use these drugs regularly. Only to be used in extreme cases and with your doctor’s approval.

What’s more?

You shouldn’t be embarrassed by this whole issue. Instead, seek the help of a professional when standard preventative measures prove futile.

A visit to the doctor is mandatory if you have any serious digestive problems, like ulcers and irritable bowel syndrome.

Manage Stress

According to a study, stress, anxiety, and other mental problems can take a toll on your stomach.

Research has linked these psychological problems with your GI tract’s ability to function optimally and adequately.

So it’s not just what you eat and drink before and during a run. What you think matters as well.

Meditate and do yoga and learn how to manage your energy channels—physical, emotional, and intellectual—right.

The psychological aspect is also vital for racers.

A race can be stressful—especially if you’re taking this whole endeavor too seriously.

Racing in a new city? Get there two to three days before the big day to get used to the unfamiliar race settings. For the race itself, stick with your successful nutrition formula.

Additional resource – Guide to runners toe

Listen to Your Body

In the end, your body knows what works the best—but there is one small caveat:

You need to be willing to listen.

Otherwise, your body’s cries for help will fall on deaf ears.

The foods and drinks you consume impact your performance and stomach—whether you want to admit it.

Therefore, practice body awareness at all times.

Learn how to gauge how your body feels before, during, and after a run and how that relates to a specific type of food or beverage.

To keep track of your experience, use a diary and keep tabs on training days in which you experienced GI issues.

Write down the symptoms and what you consumed or drank that day or night.

When to Consult A Doctor For Runners Stomach

If you regularly experience a runner’s stomach, your condition might not be directly linked with running. For example, celiac disease and irritable bowel syndrome have similar symptoms to a runner’s stomach but could also be caused by other variables.

Your doctor will assess your symptoms to figure out if what you’re experiencing is caused by running or a different diagnosis. They may also perform a colonoscopy to rule out any possible issues.

The following symptoms are signs of a serious ailment

  • Serious diarrhea that lasts for more than 24 hours
  • Acute headache that comes out of nowhere
  • Severe heart palpitations
  • Mucus or blood in the stool
  • Stubborn vomiting or nausea
  • Feeling full faster than normal
  • Unwanted weight loss
  • Loss of consciousness or fainting

GI Distress in Runners  – The Conclusion

To sum up what you should do to minimize the risk of runners’ stomach,  do the following:

  1. Think (twice or more) about the foods you are ingesting before running and the day before, and try to steer clear of high-fat and high-fiber foods at all times.
  2. Just like swimming, don’t run after a meal.
  3. Keep your body hydrated throughout the day, and take a water bottle with you for long runs, especially in hot weather conditions.
  4. Experiment with different foods and drinks and keep track using a training journal.
  5. Give your body ample time to adapt to higher training loads.
  6. In case of doubt, visit a physician and get professional help.

Here you have it.

I hope this helps.

Thank you for reading my post.

Please leave your questions and comments in the section below.

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