"Managing and Preventing Runner's Diarrhea"

From runner’s trots to runner’s colitis, a right of passage to a good story, runner’s diarrhea is such a common occurrence amongst runners that it has many nicknames. In fact, estimates suggest that runner’s diarrhea regularly plagues up to 19 percent of mile-loggers, and that up 62 percent of runners have had their workout interrupted by the need to got-to-go at some point in time. 

Runner’s diarrhea may be common, but “it is not normal, it is not fun, and it should not be normalized or accepted as inevitable,” according to gastroenterologist Will Bulsiewicz, MD, MSCI, (AKA @theguthealthmd) and author of Fiber Fueled. Turns out, runner’s diarrhea is often spurred by totally preventable factors like inadequate hydration or an irritation pre-run meal.

Rerouting your planned run, soiling your fave run shorts, and leaking like a water balloon are all about as fun as, say, a colonoscopy. So, we called up a team of gastroenterologists and registered dietitians and asked them to give us the 411 on runner’s diarrhea. Ahead, everything there is to know about what causes runner’s trots, plus how to treat and prevent it.

No, runner’s diarrhea isn’t just regular diarrhea that’s undergone a rebrand—those who travel by foot aren’t that egotistical, after all. Rather, runner’s diarrhea is diarrhea that has been induced by exercise, according to Dr. Christopher Mohr, Ph.D., RD., co-owner of Mohr Results. While “it can happen during any type of exercise that physically jostles the digestive system, it is most common amongst runners,” he says. 

The event that inspires the diarrhea isn’t the only thing that sets it apart from regular ‘ole runs, however. Texturally, runner's diarrhea is often more watery than run-of-the-mill stuff, says Dr. Mohr. Plus, it often comes with a sense of urgency while a person is out running and does not have easy access to a bathroom, says Dr. Bulsiewicz. 

Notably, “if a runner attempts to control the urge or ignores nature’s call, it can result in additional symptoms, such as waves of painful cramps and incontinence of stool,” he says. (FTR: ‘Incontinence of stool’ is a fancy way to say ‘poop your pants’).

As far as runner’s diarrhea is concerned, you can’t point your finger at just one underlying cause. “It’s multifactorial,” says Dr. Bulsiewicz. 

One of the main causes is that running literally jostles your insides, says Dr. Mohr. Indeed, the researchers of one 2014 study published in the journal Sports Medicine reported that repetitive high-impact mechanics of running contribute to lower gastrointestinal symptoms such as diarrhea and excretion urgency.

Exercise, in general, activates the sympathetic nervous system—that’s the part of the nervous system that puppeteers when your GI muscle contracts—which further stimulates gut motility, says Dr. Bulsiewicz. These muscle contractions' main job is to move stool through your body, helping produce a poop, he explains. The result of these muscles starting to contract faster when you’re pounding the pavement is that you have to poop at a faster clip than usual. 

The blood flow changes that accompany exercise are also thought to play a role. When you run, the body has to direct blood to your extremities, explains Dr. Mohr. That’s because pumping your arms and legs as you do when you’re running requires energy (called ATP), which the body can manufacture with the help of the oxygen in blood. As a result, blood gets pulled away from your color, as well as the rest of your gastrointestinal system, and directed to your limbs, he explains. 

Notably, the aforementioned research published in Sports Medicine journal suggests that the amount of blood flow getting directed to the colon is especially pronounced when the individual is dehydrated. That’s because overall blood volume drops when an individual is dehydrated, which means there is less blood overall. 

In extreme cases, the lack of blood flow to and water in the colon can cause someone to have an ischemic colon—also known as ischemic colitis, says Dr. Bulsiewicz. Ischemic colitis is marked by colon inflammation and it can lead to disruptions in the gut microbiome, “both of which are known to cause diarrhea,” he says.

This won’t surprise you, but what you eat before and during a run can also lead to runner’s diarrhea. An individual's particular GI system and food (in)tolerances and allergies will impact which eats send them running to the bushes mid-run, says Mia Syn, MS, RDN. But common culprits, she says, include greasy foods, high-fat foods, high-fiber foods, spicy foods, and sweets with sugar alcohols. 

Greasy and other high-fat foods all take a while to digest, explains registered dietitian Addie Claire Jones, an expert with TeachMe.To. So even if you ate fast food or a big ‘ole salad the night before your run, the food could still be hanging inside the GI tract when you lace up, ultimately leading to GI distress. Meanwhile, high-fiber foods can rev your gut and speed up the passage through the stomach and intensities. So, eating a high-fiber pre-workout meal (like an apple, bran, or whole grain toast) can exacerbate the got-to-go feeling. And, the spices in spicy foods can irritate the lining of your digestive tract, especially if you are not accustomed to consuming them.

Finally, Dr. Mohr says the body lacks the digestive enzymes necessary to break down sugar alcohols (like erythritol, maltitol, and xylitol) and most artificial systems. Research published in the International Journal of Dentistry reported that they can cause a particular type of irritation-induced diarrhea, medically known as osmotic diarrhea.

The good news: Runner’s trots are an inevitable side-effect of feeling the wind on your face and trail (track or tread) under your feet. Ahead, 6 expert-backed tips for reducing your risk of runner’s diarrhea.

While eating the wrong thing before a run can lead to runner's diarrhea, running on empty (literally) can cause tummy distress, too. “Your gastrointestinal system might react poorly to the combination of insufficient fuel combined with physical stress,” explains Dr. Mohr. As such, he recommends finding which pre-run snacks and meals that work for your body.

“If you're eating an hour to 30 minutes before your run, choose a meal that's low in fiber, protein, and fats and is predominantly simple carbohydrates,” suggests Dr. Mohr. A simple slice of toast or banana will serve you well here.

“If you have more time, 2 to 3 hours, you can have a more substantial meal that includes some complex carbohydrates and protein,” he says, as there is sufficient time for digestion. A bagel with peanut butter, omelet with toast, oatmeal with add-ins, or a protein with potatoes are all decent pre-run meal options.

Being dehydrated doesn’t just exacerbate symptoms of runner’s diarrhea—it can also cause feelings of fatigue and lightheadedness, which at worst can make running downright dangerous.

“It’s super important to make sure you’re well-hydrated before you head on your run,” says Dr. Mohr. Mohr. The key is to regularly be ingesting fluids, even on your rest days, so that you’re consuming a minimum of 6 to 8 cups in addition to whatever you intake while on the run. Though, your baseline needs will increase if you are a heavy sweater, live in a warm climate, work a high-activity job, or have a bigger body. (The simplest way to tell if you are dehydrated is to peek in the Golden Throne and make sure you don’t see, well, gold or try the skin pinch test).

“While you run you’ll also want to make sure that you’re keeping up with your hydration needs —especially on longer runs,” says Dr. Mohr. One study published in the journal of Sports Medicine found that there isn’t a universal recommendation for long-distance runners, given that sweat volume varies. As such, the researchers recommended that every runner learn how much fluids they personally need to consume while running in order to prevent a >2% loss of body mass, which is the point where performance gets impacted. To do this simply weigh yourself (preferably naked) before and after exercise, then be sure to drink that weight in fluids in future runs.

Staying properly hydrated doesn’t start and stop with fluid intake—electrolyte balance matters, too. Electrolytes play a crucial role in fluid balance, Chris Ryan, CSCS, NSCA-CPT previously told Shape. When you get hot, you don’t just lose water when you sweat, you lose electrolytes (especially sodium), too.

As your runs get longer, replenishing electrolytes is essential for maintaining proper overall hydration. When you’re on the go, sports drinks (think: Gatorade and Powerade) and electrolyte-packed powders come in handy. However, if you discover that those options upset your tummy and your run pack has space, consider gnawing on natural options like banana or orange slices.

If you’re running longer than an hour, Dr. Mohr suggests trying out different mid-run sports drinks and snacks, to see what agrees with your GI system. The hour-mark is usually when an individual uses up their glycogen stores, which the body relies on for easy energy. When glycogen (basically, sugar) stores get used up, the body can turn to fat and protein as energy—however, it’s less taxing for the body to burn glycogen, so when glycogen stores get depleted an individual can start to feel fatigued. Not ideal!

Re-upping your glycogen stores through sports drinks and carbohydrates can help replenish those stores, says Dr. Mohr, thus reducing feelings of fatigue so you can log as many miles as are on top. Figuring out which mid-run snack works best will likely require some trial and error (runner trots), per Syn. “Energy gels, goos, bars, and chews can be great, but they can contribute to diarrhea in some people,” she says. Options without caffeine, sugar alcohols, and fructose are the least likely to cause GI-distress.

“Maintaining a lifestyle outside of running that supports a healthy gut will help to protect you from runner’s diarrhea,” says Dr. Bulsiewicz. “This is accomplished by eating plenty of plant based and fibrous foods and considering a daily probiotic and prebiotic supplement,” he says.

“The sensation of tight clothing around the midsection can potentially worsen runner’s diarrhea, in particular if they are right enough to constrict blood flow to the intestines,” says Syn. As such, she suggests people prone to runner’s trot wear looser clothing while logging miles. (In the event that you need to give your workout wardrobe a makeover keeping this in mind, consider these affordable options from Amazon).

If you start to experience the hallmark symptom (urgent diarrhea) of runner’s trots in the middle of your workout, find a porta-potty as soon as possible, suggests Dr. Bulsiewicz. Trying to hold it in can lead to cramping, he says. Not to mention the risk of shitting your pants (er, leggings) isn’t zero. Research is limited, but one 1992 study published in the Journal of Clinical Gastroenterology found that 12 percent of runners have had an accident while running.

After you go, Syn suggests either calling it for the day, or dropping the intensity for the remainder of your run. “Reducing intensity of your run will reduce the stress on your digestive system,” she explains.

You’ll likely also want to focus on your electrolyte and water intake following your flux. Diarrhea—especially that which comes on suddenly and violently, as is the case with runner’s diarrhea—can cause a tremendous loss of water in a short period of time, which can cause dehydration, says Dr. Bulsiewicz. In fact, dehydration is the most severe threat of diarrhea, per the World Health Organization.

How you choose to re-hydrate matters, too. “Do not try to 'fix' your dehydration by chugging two electrolyte packets,” says Jones. This can exacerbate pre-existing fluid imbalances and actually lead to more diarrhea, she says. Instead, stick with one electrolyte mix, or opt for one serving of a commercial rehydration solution, such as Gastrolyte or Pedialyte.

Runner’s diarrhea usually goes away on its own—in fact, most people experience relief immediately after a mid-run poop pit-stop. However, if the condition lasts more than 2 days you should consult with a healthcare provider, as the diarrhea could actually be a symptom of an underlying gastrointestinal virus (like norovirus), bacterial infection (like e.coli or salmonella), or a parasitic infection (like giardia), according to the National Institute of Diabetes and Digestive and Kidney Diseases.

You should also consult a healthcare provider if your stool is bloody. “Seeing blood in your stool is a sign that you may have pushed your body too far,” says Dr. Bulsiewicz. Bloody bowel movements are also a symptom of a range of conditions, including ischemic colitis, irritable bowel syndrome and ulcer disease. On a similar note, you should also seek out the counsel of a gastroenterologist if runner’s diarrhea is regularly ruining your runs. While it's possible for anyone to experience runner's diarrhea the morning after a spicy meal, regular issues nod to a chronic GI condition, like irritable bowel syndrome (IBS) or colitis.