How to Get Through an Ironman Without Sh*tting Yourself

Nothing can stop you from feeling like #1 on race day - except for #2. Sports certified Registered Dietitian Susan Kitchen explains how to prevent GI distress and stay out of the port-a-potty.

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Nothing can stop you from feeling like #1 on race day—except for #2. Cramping, diarrhea, and endless port-a-potty stops will ruin race day more than almost anything else Mother Nature can serve up. But it happens to the best of us, so let’s address the elephant in the room with this complete guide to preventing a crap catastrophe at your next race. 

RELATED: Triathlete’s Complete Guide to Nutrition and Fueling


Photo: Rick Madonik/Getty Images
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What causes gastrointestinal (GI) distress during a race?

GI distress originates from the upper and lower intestines. Common upper GI symptoms include belching, nausea and vomiting, heartburn and reflux, and bloating. Lower GI symptoms involve abdominal cramping, gas, side stitch, diarrhea or loose stools, urgency to defecate, and intestinal bleeding.  

Symptoms of GI distress happen in any part of a triathlon. In the swim, swallowing air from short, rapid breathing can result in belching. Likewise, bike posture can put pressure on the abdomen causing stomach pain, reflux, and belching. But the inherent jarring nature of running jostles the stomach and colon more than in any other sport – hence the term “runner’s trots.” This mechanical stress causes food and waste to move through the GI tract more rapidly, all the while blood is being shunted away from the intestines toward the working muscles, reducing functionality of the GI tract

Athletes with pre-existing GI issues such as reflux, lactose intolerance, inflammatory bowel disease, and irritable bowel syndrome are more likely to experience GI symptoms during competition. Taking extra precautions to avoid possible triggers before race day would be well-served. 

RELATED: A Physiological Look at What the Body Goes Through During an Ironman

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How to prevent cramping, bloating, and diarrhea during a race

Everybody poops, but when it comes to race day, we’ll do just about anything to avoid doing it after our final pre-race port-a-potty stop. Luckily, there has been mounting research into the prevention of gut complications in athletes over the past several years. Although every athlete is different and no one size fits all, hopefully one or two of the following strategies will help mitigate the chance of you spending more time in the toilet than in the actual race. 

How to preventing GI distress during a race: 1-3 days out

Avoid high-fiber foods

A few days leading up to a race or key workout, reduce or avoid high-fiber foods such as cruciferous vegetables (broccoli, Brussels sprouts, kale, and cauliflower), high-fiber cereals, and brown rice. Instead, choose low-fiber foods like white bread, rice, potatoes, and pasta. 

Skip the NSAIDs

Avoid aspirin and non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen. These drugs have been shown to increase intestinal permeability, mucosal bleeding, ulcers, and incidence of GI complaints.

Ditch dairy, fructose, and sweeteners

If lactose intolerant, avoid dairy products or substitute with lactose-free or dairy-free alternatives. Soy, rice, and almond milk are safe bets. 

You’ll also want to stay clear of high fructose foods and beverages such as soda, juice, candy, sweetened carbonated drinks, and dried fruit. Fructose is absorbed by the intestine slower than glucose and can contribute to cramping, loose stool, and diarrhea.

If you are a fan of low-calorie or sugar-free drinks, consider kicking them to the curb. Unlike other foods, sugar alcohols or artificial sweeteners such as sorbitol and aspartame are not absorbed by the body, so they pass through the intestines mostly intact, pulling water with them. Symptoms include gas, bloating, and urgent bowel movements.

Reduce fat intake

Reduce fat intake in the 12–24 hours before your race begins. Fat slows down digestion which means if you have a fried pre-race dinner or a heaping plate of bacon on race morning, the body will be digesting it long into your race—well, until it ends your race.

Skip gluten if you’re intolerant

Athletes diagnosed with Celiac disease or gluten intolerance should avoid all foods that contain gluten. However, if you don’t have one of these diagnoses, there is no scientific evidence that gluten is your problem.

Cut back on caffeine

Many athletes swear by their morning cup of coffee to wake up and maintain #2 regularity. Though it’s true that coffee can have a laxative effect, not everyone jives with caffeine. Excessive caffeine use, especially during intense exercise, can contribute to GI distress. Rule out caffeine – both in your morning coffee and in your sports nutrition – as the culprit of your GI distress in training, so you know what’s safe to use on race day.

RELATED: 10 Things the Latest Science Tells Us About Caffeine and Athletes

Keep a food log

The best way to detect the food(s) triggering your gut is to keep a food and bowel journal alongside your training log. Although emergency pit stops are hard to forget, what we ate before the training session can easily slip our minds. Keep in mind that the cause of your GI distress may not be what you ate immediately before training; it takes approximately 24–72 hours for food to move through the gut to the toilet. Keeping the log can help you identify patterns in your nutrition and gut function.

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Prevent and manage GI distress during a race

Develop and test your fueling and hydration plan

Just as we train the muscles and mind to perform while swimming, cycling, and running, the gut must also be trained. In the weeks and months leading up to race day, it’s important to practice processing your chosen sports fuel at race day intensity, temperature, and humidity.

The best strategy is to establish a fueling and hydration plan and test it out in training repeatedly for months leading up to your race. Use simulated race day training sessions, such as long rides, long runs, and brick workouts, to practice your fuel plan. Test-driving a fuel plan months before race day provides a chance to identify whether a product disagrees with your body and time to find a suitable replacement.

Eat your pre-race breakfast at least 2.5 hours before the race begins

Eating too close to training or race start is one of the biggest nutritional mistakes you can make. To avoid this mishap, establish a pre-race breakfast that has repeatedly proven successful in training and aim to have it at least 2.5 hours before race start. As any athlete knows, all bets are off on race day when it comes to eating. So on race morning, if your pre-race breakfast isn’t going down easily, then eat what you can comfortably; don’t force it. Either way, focus on hydration but don’t over-hydrate. More is not always better.

RELATED: The Expert-Curated, Triathlete-Approved Race Week Menu

Learn to manage pre-race nerves

Race day nerves aren’t all bad, said the constipated athlete, who appreciates the opportunity to empty the bowels. Plus, we know that our pre-race jitters are preparing the body for the work that lies ahead. But, for the athlete who struggles with frequent port-a-potty visits, the jitters only add fuel to the fire. To counter this disruption, create a race morning routine to manage and mitigate the nerves. Your bowels are a creature of habit, so get up early, have a small breakfast, and use the bathroom in peace and quiet. You might also consider a short shakeout run several hours before the race as a kickstart to get the intestinal system moving.

RELATED: New Research Shows Anxiety Contributes to GI Distress

Know your carbohydrate limits

Athletes who limit or avoid carbohydrates (carbs) in daily life and training have significantly reduced their ability to absorb carbs. So, come race day, when you start fueling with carbs, the body won’t be able to effectively absorb it, thus leading to GI issues. Don’t limit carbs; it’s the body’s choice fuel in daily life and training.

To fast track the body’s ability to absorb carbs in training, sports nutritionist Asker Jeukendrup recommends mixing sugar types and increasing your carb volume during training in order to train your stomach to tolerate higher volumes and empty more efficiently. Luckily for the 50% of triathletes who have had stomach problems, this can raise your carbohydrate absorption rate by over 30% in less than two weeks.

RELATED: Which Foods to Avoid at Aid Stations


Dehydration will not only wreck your performance but also increase the probability of GI distress by reducing blood flow to the intestinal system. Adhering to a well-established hydration strategy to offset sweat loss and prevent the body from exceeding 4% weight loss will help mitigate dehydration-related GI issues.

Sports drinks with >8% carbohydrate concentration, gels without adequate water for dilution, and solids containing protein, fat, and fiber via bars or other solid food contribute to dehydration, further exasperating GI upset. Create a fuel plan with an appropriate fluid and carb balance to avoid overloading the gut.

Live by the mantra, ‘sip early and often.’ Don’t wait 30–45 min on the bike to start sipping from your bottles. To optimize gut emptying, take frequent small sips and bites throughout the ride and run instead of drinking half the bottle an hour into the race making up for lost time.

Pace yourself and stay cool

No matter how good you feel coming out of T1, just because you can hit the gas doesn’t mean you should. Instead, aim for a smooth effort you can build on. Going too hard too early will shut down the gut, causing bloating and a sloshy stomach, sabotaging your race right out of the gate.

Although further research is needed, cooling the body with cold drinks, ice, sprinklers on course, and/or pre-race heat acclimation protocols seem promising at reducing gut complications in hot conditions.

Photo: Jiri Studnicky
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Should I take anti-diarrhea drugs during a race?

When all else fails, many turn to their medicine cabinet or pharmacy looking for the magic elixir to save them from another disappointing race experience.

Anti-diarrhea drugs such as Imodium or Kaopectate are mainstream choices. Medical experts support taking a single dose about an hour before a major race, so long as it doesn’t cause bloody diarrhea; however, these experts also warn it shouldn’t be a daily fix.

Other nutritional supplements that claim to reduce gut complications during activity are glutamine, arginine, L-citrulline, antioxidants, curcumin, nitrate, bovine colostrum, and ginger. However, based on current evidence, there is no scientific justification for the use of nutritional supplementation in the prevention or management of gut issues during activity.

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How to prevent GI distress during a race: The bottom line

Just as in training, there are no shortcuts to preparing and training the gut to process appropriate sports fuel into usable energy (glucose) for the body. Race day can be hard enough, so do everything in your power to make fueling easy for the body. That means dial-in a simple fuel-hydration plan made up of easy-to-digest carbs and well-formulated sports drinks at least 6–8 weeks before race day. Then, to set yourself up for success, test drive it every chance you get in training so that your body knows it intimately—so come race day, we spend less time in the port-a-potty and more time on the race course!