As someone with celiac disease and ulcerative colitis, I have a highly sensitive digestive tract and had my fair share of experience with gastrointestinal problems.
As a kid, I was quite self-conscious about my frequently upset stomach and all of the foods I had to avoid in order to maintain some semblance of a calm gastrointestinal system.
However, while I certainly felt alone in my digestive woes when I was young, once I started running, I suddenly had a whole flock of new friends who were not afraid to talk about their loose bowel movements and urgent need to go while running.
Indeed, while many people seem to have no gastroenterology issues on a day-to-day basis, once you throw in long-distance running, all sorts of stomach issues can occur, one of the most common being runner’s diarrhea.
The dreaded sudden urge to run to the toilet or find the nearest woods to dart into to relieve yourself is not a foreign phenomenon to many marathon runners and long-distance runners.
In this guide to runner’s diarrhea, we will discuss the causes and give you tips for how to prevent runner’s diarrhea to hopefully help you have blissful runs and stress-free race days that don’t require toilet paper!
What Is Runner’s Diarrhea?
Runner’s diarrhea, also called runner’s trots or runner’s colitis, refers to the urge to poop while running or diarrhea after running.
The bowel movements may be accompanied by cramping and gas, and stools may be loose or runny and frequent or sudden.
Runner’s diarrhea is one of several gastrointestinal issues common in long-distance runners that sometimes fall under the umbrella of “runner’s stomach.”
Symptoms of runner’s diarrhea may be accompanied by abdominal pain, stomach cramping, side stitches, gas, bloating, belching, and irritation of the butt after pooping.
What Are The Causes Of Runner’s Diarrhea?
Studies have found1Samborski, P., Chmielarz-Czarnocińska, A., & Grzymisławski, M. (2013). Exercise-induced vomiting. Przegla̜d Gastroenterologiczny, 8(6), 396–400. https://doi.org/10.5114/pg.2013.39924 that up to 83% of marathon runners complain of various gastrointestinal symptoms during or after running, including upset stomach, cramping, the urgent need to make a bowel movement mid-run, or loose bowel movements after running.
Clearly, there must be something about running that causes diarrhea or other gastrointestinal problems.
But, why does running make you poop more?
There are various causes of runner’s diarrhea, including the following:
- Experts suggest2ter Steege, R. W. F., & Kolkman, J. J. (2012). Review article: the pathophysiology and management of gastrointestinal symptoms during physical exercise, and the role of splanchnic blood flow. Alimentary Pharmacology & Therapeutics, 35(5), 516–528. https://doi.org/10.1111/j.1365-2036.2011.04980.x that runner’s stomach can be caused by the actual jostling and mechanics of the running motion and hormonal factors
- Not waiting long enough after eating before running
- Drinking sugary beverages and eating high-carbohydrate foods3Morton, D., & Callister, R. (2014). Exercise-Related Transient Abdominal Pain (ETAP). Sports Medicine, 45(1), 23–35. https://doi.org/10.1007/s40279-014-0245-z for pre-run or mid-run fueling
- Dehydration, especially if running in hot weather
- Drinking water too quickly while running or right after running
- Eating fatty foods, high-fiber foods, foods high in sorbitol and sugar alcohols, and high-protein pre-run snacks and meals, since these foods delay gastric emptying and can increase bloating when running
- Running too fast
- Taking non-steroidal anti-inflammatories (NSAIDs) such as ibuprofen before running increases the risk of ischemic colitis (decreased blood flow to the large intestines)
- Hyperventilating or breathing with an uneven pattern during intense exercise can cause stress on your diaphragm.
- The stress and anxiety experienced on race day morning
- Excessive caffeine intake, such as drinking coffee before running or taking caffeinated energy gels or a pre-workout supplement with caffeine
What Can I Do To Prevent Diarrhea While Running?
Here are some tips for preventing runner’s diarrhea and other gastrointestinal problems while running:
#1: Eliminate Foods That Cause Gastrointestinal Issues
An urgent need to poop mid-run is more likely if you’re eating foods that upset your stomach.
There isn’t a definitive list of foods that cause diarrhea while running or an upset stomach during a run for all long-distance runners.
Depending on the sensitivity of your digestive tract and any underlying gastrointestinal issues you may have (such as IBS, celiac disease, etc.), certain foods may cause runner’s diarrhea more than others, particularly if you eat them in your pre-run meal or snack.
For example, if you are lactose intolerant, any dairy products can cause a build-up of gas in your intestines and colon, causing gas, abdominal bloating, and loose bowel movements.
Aside from individual food sensitivities, there are certain foods that tend to increase gas production for most people.
These include foods high in fiber (beans, wheat bran, avocados, etc.), foods or drinks high in sugar alcohols like sorbitol or maltitol, and foods high in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs),4de Oliveira, E. P. (2017). Runnerʼs diarrhea. Current Opinion in Gastroenterology, 33(1), 41–46. https://doi.org/10.1097/mog.0000000000000322 such as onions, garlic, and cauliflower.
These foods can increase fermentation by the bacteria in your gut, which leads to excessive gas production that will get trapped in your stomach and intestines.
#2: Rethink Your Hydration
Many people get stomach cramps or diarrhea while running because they are either dehydrated or drink water too quickly.
Additionally, sports drinks can also cause runner’s diarrhea.
Sports drinks that are high in simple sugars and contain too much sodium, or “sugar-free“ sports drinks that contain artificial sweeteners or sugar alcohols, can throw off your electrolyte balance and cause an upset stomach, gas, and loose bowel movements.
All of these ingredients can cause excess fluid to flood the intestines, leading to loose, watery stools. In addition, artificial sweeteners are not digested well, so they can cause cramping, flatulence, and loose bowel movements.
According to research, the ideal concentration of carbohydrates in these electrolyte drinks is 6-8%, with an overall goal of ingesting 30–80 grams of carbohydrates per hour for workouts lasting over 90 minutes.
#3: Wait Long Enough After Eating to Run
It’s common to get diarrhea or stomach cramps while running if you run too soon after eating.
Plan to wait about 3-4 hours to run after eating a large meal, 2-3 hours for a small meal, and 1-2 hours after most snacks unless it’s a very small snack consisting of only simple carbohydrates and you’re doing a very low-intensity, slow recovery run.
Some runners prefer running first thing in the morning on an empty stomach because they are either more “fat adapted“ which means that their body is better able to use fat for fuel at higher intensities, or they are doing shorter workouts, running at a slower speed, or otherwise feel better running on an empty stomach.
#4: Stop Consuming Artificial Sweeteners
Another often overlooked reason for experiencing runner’s diarrhea is because of the artificial sweeteners and sugar alcohols found in many sugar-free protein bars, protein powders, chewing gum, and low-calorie sports drinks.
Sugar alcohols, in particular, have been shown to have a laxative effect,5Ruiz-Ojeda, F. J., Plaza-Díaz, J., Sáez-Lara, M. J., & Gil, A. (2019). Effects of Sweeteners on the Gut Microbiota: A Review of Experimental Studies and Clinical Trials. Advances in Nutrition, 10(suppl_1), S31–S48. https://doi.org/10.1093/advances/nmy037 and cause diarrhea, stomach upset, bloating, gas, nausea, and flatulence.
#5: Cut Down On Pre-Run Fat
It used to be that marathon runners would almost exclusively fuel with carbs in a pre-run or mid-run snack, but with the prevalence of the keto diet and low-carb diets, many long-distance runners are having high-fat pre-run meals or snacks.
Some people’s bodies do not absorb fat particularly well, and bile, which is released by the gallbladder when you consume a high-fat meal, is a natural laxative.
Together, these issues with a fatty pre-workout snack can cause loose, greasy stool, especially if you are new to the keto diet or have had your gallbladder removed.
Stick with low-fat pre-run foods.
You should use your longer training runs to practice your fueling and hydration strategy, including some of your tempo runs for longer runs that have goal pace miles in them to make sure that your stomach can handle digesting the carbs and electrolytes you are taking in as your chosen race fuel.
You can’t do much about the mechanical jostling of running, but easing into a high-intensity workout by doing a warm-up may help the blood flow shifts that occur once you start exercising (away from the digestive tract and to your working muscles) to be more gradual.
Similarly, a cool down after a high-intensity workout can help gradually (instead of suddenly) restore blood flow to the digestive tract to prevent diarrhea after running.
One final tip is that you can take Imodium or an anti-diarrheal on race day if you are really concerned about needing to poop during the race, but this is not medical advice, so you should consult your healthcare provider first.
If you are still having issues with runner’s diarrhea, you should speak with your doctor or gastroenterologist to figure out if you have any underlying gastrointestinal problems such as irritable bowel syndrome, celiac disease, or food sensitivities that might be contributing to digestive problems while running.
For some ideas on pre-run snacks, check out this next guide:
