Become a Member

Get access to more than 30 brands, premium video, exclusive content, events, mapping, and more.

Already have an account? Sign In

Become a Member

Get access to more than 30 brands, premium video, exclusive content, events, mapping, and more.

Already have an account? Sign In


Race Fueling

How Food Intolerance Could Be Affecting Your Performance

GI complaints are among the most common and frequent complaints of endurance athletes, in particular runners.

Heading out the door? Read this article on the new Outside+ app available now on iOS devices for members! Download the app.

In her new book The Athlete’s Fix, a sports nutritionist and pro triathlete explains how food intolerance and your nutrition could be affecting your performance. Republished from The Athlete’s Fix by Pip Taylor with permission of VeloPress. Learn more at

Knowing that athletes can be more susceptible to food intolerance as a result of their lifestyle and the demands they place on their body, it’s helpful to think about how the symptoms of food intolerance could be playing out in your own performance or plateau, as the case may be. It’s quite possible that you’ve come to accept some of these problems as the plight of being an athlete. Or maybe you pin them on a lack of fitness, lackluster genetics, or the stress of everyday life. It’s entirely possible that your performance problems, including those tied to GI issues, could be fixed with some changes to your diet.

Gastrointestinal specialists, dietitians and nutritionists spend a lot of time talking about bowel movements. In my experience, the same thing can be said of athletes. Although there are those athletes who remain a little more shy, I can guarantee they are still thinking about it—and for good reason: GI complaints are among the most common and frequent complaints of endurance athletes, in particular runners. The feeling of urgency that hits during exercise is often called “runner’s guts,” a state that is widely accepted as part and parcel of being an athlete. It is estimated that the vast majority of runners, somewhere between 60 and 90 percent, have experienced some sort of gastrointestinal distress: nausea, diarrhea, stomach cramps and pains, bloating and burping. I would argue that every runner experiences GI issues over the course of his or her years of training and racing. Those who haven’t are either lying or are new enough to the sport to be unaware of the joys that lie ahead for them.

GI distress results from the reduction in blood flow to the gut, which occurs during exercise, and at the same time from the relaxation of the gut’s muscular tone, which comes as a result of the actions of the sympathetic nervous system. This combination of events can move the contents of the large intestine, rushing them through to your rectum and causing plenty of urgency as you desperately look around for the nearest restroom or bush. When we think of runner’s guts, we typically think of GI symptoms that happen in the middle of a workout or race, but they are also common after exercise.

Upper GI distress manifests as heartburn, vomiting, belching, bloating, nausea and/or stomach pain, and lower GI distress includes cramping, gas, urgency and diarrhea. Women report more GI distress than men, and lower GI complaints are more common than upper. Both the intensity of the physical effort as well as type of exercise will influence symptoms; naturally, higher intensities and weight-bearing activities, such as running, generally lead to more pronounced symptoms.

GI issues are not something that you have to put up with if you want to be active. If you suffer from frequent, ongoing issues, dig a little deeper to find the cause. Antidiarrheal or antinausea medications are not the solution. There is evidence that these medications can interfere with hydration, which will inevitably lead to more problems. For some athletes, GI issues have nothing to do with food intolerance—it’s simply a matter of timing. Foods that are high in protein, fat or fructose are generally not well tolerated by anyone during exercise and can lead to GI distress. Such food is too much for your stomach to deal with, and the anxiety and nerves that accompany a big effort only further reduce your body’s ability to digest. By simply adapting the foods that you eat in the lead-up to a big workout or race, or by more carefully timing those foods, you might be able to solve the problem.

To complicate things, there are foods or food components that are more difficult to address. For example, many sports foods contain fructose, a sugar that can cause GI problems when it becomes too highly concentrated in the stomach. Some athletes can manage their intake of fructose or avoid it during intense exercise. For others, it can be a true intolerance.

If your reaction to a food is caused by exercise, it’s possible that you can do something about it. Like any other muscle, the gut can be trained to better tolerate different foods during exercise—solids as well as liquids, and also fats and fiber. Gut training can also help you better tolerate a greater volume of a given food. In other words, gut training won’t solve an intolerance but can increase your tolerance for specific foods during exercise, which leads to more effective fueling.

GI issues can be devastating to your plans for race day. The physiological effects are generally short-term—once you stop exercising, rehydrate and eventually ingest some well-tolerated foods, you will find yourself in a much better place. Severe GI issues are not so easily reversed, and they can lead to blood loss in the stool as a result of extreme blood flow restriction, causing either mucosal erosions or shutdown of some sections of the gut. These scenarios can cause long-term problems and require medical attention. GI issues caused by hidden food intolerances, no matter their severity, not only affect your performance in a given race, they can ultimately lead to nutrient deficiencies. Any time you are dealing with ongoing diarrhea or nausea or other GI symptoms, it can interfere with healthy ingestion and absorption, and this is a problem that must be addressed.

RELATED: 7 Simple Food Swamps For Better Nutrition

Cause and Effect

Here are the foods and habits that often cause GI distress for endurance athletes that can help you troubleshoot the cause(s) of your
GI issues.

Food intolerance: Which can be exacerbated by exercise stress
FODMAPs: A kind of carbohydrate
Fructose: Commonly found in sports foods and drinks
Lactose: Found in varying levels in dairy products
Caffeine: Found in coffee, tea, soft drinks, chocolate, sports foods
Meal timing: Eating too close to exercise, increasing pressure on the gut
Fat and fiber: Too much of either can rush things through your GI tract
High-carb sports drinks: Dehydrate your gut before they rehydrate you
Dehydration: Can wreck your gut
Stress: Key workout or pre-race nerves can make you run for the Porta-Potty.
NSAIDs: Can cause leaky gut syndrome
Antibiotics: Can decimate your gut biome
Posture (especially in cycling): Puts physical pressure on your gut
– Vibration: Jarring motion of running and jumping, which is obviously unavoidable
– Antidiarrheal and antinausea meds: New research shows these meds interfere with hydration and make things worse for athletes, not better.

What are FODMAPs?

In some people, certain carbohydrates eaten in threshold amounts can lead to symptoms such as bloating, gas, distension, abdominal discomfort, and either diarrhea or constipation, or a mix of both. The bacteria residing in your gut will determine how you handle and respond to these particular carbohydrates.

The types of carbohydrates that are most commonly malabsorbed in the intestine are known as FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols). These are simply the technical names for the structure of the sugar molecules (saccharides is another name for sugar). All carbohydrates are broken down into glucose or sugar molecules through digestion.

FODMAPs are found in a wide variety of foods: fruits, vegetables, grains, legumes, dairy, nuts, and seeds. Apples, pears, onions, garlic, wheat, and rye are among the common culprits. Since FODMAPs describe only certain carbohydrates, proteins and fats are free of them.

Guidelines for a Healthier Gut

One of the first steps to resolving your GI issues is healing your gut by reducing inflammation and foods that commonly make GI issues worse. Time is part of the equation to allow your gut to recover and repair, but these other dietary and lifestyle habits are also key.

Stick to anti-inflammatory foods for the majority of your dietary intake. Inflammatory foods kill off good gut bacteria and encourage growth of bad bacteria.

Incorporate more fermented foods (e.g., kombucha, sauerkraut) and probiotics into your diet. Research shows that probiotics help maintain healthy gut bacteria populations and the overall integrity of gut barrier function, thus preventing leaks and reducing the risk of toxins entering the bloodstream and thereby inflammatory reactions and food intolerances.

Prebiotics, a fancy word for the fibers found in plant matter, are just as important to provide food for the probiotics. Stock your diet with vegetables, fruits and nuts to provide lots of fermentable fiber, which will serve as food for the probiotics.

Only use antibiotics as needed, and avoid animal products that have been exposed to antibiotics.

As an athlete you can encourage a healthy population of bacteria within your own gut by steadily building fitness and not overreaching. Appropriate workouts and timing will help facilitate positive acute stress that induces adaptation, allowing you to become fitter, faster and stronger and strengthen your immune system. But the chronic stress that can occur with overtraining, inadequate recovery or trying to achieve too much before you are ready for it can compromise body functions and structures, including that of the digestive tract and the resident bacteria.

Stay hydrated. Adequate hydration helps maintain the gut wall’s cellular structure (important as a barrier) as well as its function

Step One

The first step of The Athlete’s Fix is cleaning up your diet by adopting the Base Functional Diet. On the Base Functional Diet, you’ll avoid common problem foods, inflammatory foods, food ingredients, chemicals and habits that can trigger food sensitivity symptoms or make food intolerances worse. During your time using the Base Functional Diet, you will reduce your overall levels of inflammation, heal any damage to your gut, reduce your chronic load of food-related allergens, and return gradually to a base state. Don’t think of the Base Functional Diet as a cleanse, which it is not. Think of it instead as a grace period to allow your body a much-needed break from the irritants that are causing your reactions to food. Most people begin feeling better in just a few days. The Athlete’s Fix offers 50 recipes to support the Base Functional Diet. Here are two to try.

Banana Cinnamon Bread

Serves 5 (10 generous slices)
When I make banana bread, I use different flour combinations to allow for different intolerances or allergies. This variation uses coconut flour, which gives the bread nice flavor and a lot of fiber. I also use plenty of cinnamon; if you want a subtler flavor, use just 1 teaspoon. Change up the add-ins—use dried fruit for naturally sweeter bread or use nuts to add texture and a bit more fat and protein. For a real treat, try adding dark chocolate chips.

Scant ½ cup coconut flour
1 tsp gluten-free baking powder
1 T cinnamon
Pinch of sea salt
¼ cup unsweetened dried cranberries, raisins or chopped walnuts
2 large (or 3 medium) very ripe bananas
5 large eggs (or 6 small ones)
1 tsp vanilla extract
¼ cup coconut oil, melted

Preheat the oven to 350 degrees F. Line a 4×8-inch loaf tin with parchment paper.

Combine the coconut flour, baking powder, cinnamon, salt and dried fruit or nuts in a medium-sized bowl. In a separate bowl mash the bananas, then add the eggs and whisk to combine. Stir in the vanilla and coconut oil. Add the wet ingredients to the dry ingredients and mix well.

Pour the batter into the prepared loaf tin and bake for 30–40 minutes. Remove from the oven when the loaf is golden on top and a skewer or toothpick inserted into the middle of the loaf comes out clean. Let rest for 5–10 minutes before slicing and serving.

Slow-Braised Beef Ribs With Cauliflower Puree

Serves 6

When you don’t have much time to cook, slow-cooking can be the answer. Light on actual prep time, slow-cooked dishes are full of flavor and forgiving of imprecise cooking, and they take advantage of the cheaper cuts of meat. These dishes also store and freeze really well. Cooking meat on the bone means you not only add lots of extra flavor, but you also get some of the mineral goodness that comes from the bones.

Ingredients for beef ribs
1 T olive oil
3½ lb. beef ribs (about 6 ribs)
1 medium yellow onion, chopped
4 carrots, peeled and roughly chopped
4 celery stalks, roughly chopped
1 cup red wine
1 cup beef or vegetable stock or water
1 cup tomato purée
2 bay leaves
Sea salt and pepper
2 T fresh parsley, chopped
Zest of 1 lemon

Ingredients for Cauliflower
2 large potatoes, peeled and cubed
1 head cauliflower, roughly chopped
2 T olive oil
1 T fresh parsley, chopped
Sea salt and pepper

Preheat the oven to 325 degrees F. In a large, heavy, oven-safe pot, heat the olive oil over medium heat and add the beef ribs. Cook, turning often, until the ribs are brown all over, then remove them from the pot and set aside. Increase the heat to high and add the onion, carrot and celery. Cook, stirring, until the onion begins to soften. Add the red wine and scrape down the sides and bottom of the pot. Return the ribs to the pot, turn down the heat to low, and add the stock or water, tomato purée and bay leaves. Season with salt and pepper to taste.

Put the pot into the oven and cook for 3–4 hours. Alternatively, leave the pot on the stove, bring to a gentle simmer, cover and let cook gently for 3–4 hours. The meat will fall off the bone when it is cooked.

To make the cauliflower purée, about 30 minutes before the ribs are finished cooking, bring a large pot of water to boil. Add the chopped potato and cook until tender, about 10–15 minutes. Add the cauliflower and cook for another few minutes until both the potato and cauliflower are quite soft. Drain and return to the hot pan. Purée using an immersion blender or a potato masher. Add the olive oil and parsley, and season with salt and pepper to taste.

Divide the purée into bowls, then top with the beef ribs. Sprinkle with the chopped parsley and lemon zest to taste. Serve immediately.

Republished from The Athlete’s Fix by Pip Taylor with permission of VeloPress. In The Athlete’s Fix, Taylor, a certified sports nutritionist and professional triathlete, shares a sensible, effective program to find your food allergies and sensitivities, heal your gut and develop your own customized clean diet that will support better health and performance. Learn more at

Video: 4X World Champion Mirinda Carfrae Makes Her Picks for 70.3 Chattanooga

Carfrae and former pro Patrick Mckeon break down the iconic course in Chattanooga, who looks good for the pro women's race, and their predictions for how the day will play out.