Do Your Food Intolerances Interfere with Your Fuel Plan?

Don’t let stomach issues stand between you and your next PB. Here’s how to sidestep issues that can derail you.

The horror stories vary from runner to runner. Some sense something is amiss as they toe the starting line; others make it midrace before they’re inevitably overtaken. But each tale ends the same: with a sinking stomach, gurgling gut, and a frantic pitstop at the nearest porta loo (if you happen to be so lucky). With your PB slipping away, you rack your brain for everything you’ve eaten in the last 24 hours.

Was it the pasta last night? The oatmeal this morning? Did I try something new?

In hindsight, it can be hard to pinpoint exactly where your fuelling went wrong. And it only makes us feel worse when we just can’t figure out the root of the problem. Maybe you ate too close to your race, or your nerves are to blame. Or, you may actually have a food intolerance.

Food intolerances are different from food allergies. “An allergy is an immune response, is much more serious, and can be deadly,” says Leslie Bonci, R.D.N, a sports dietitian and owner of Active Eating Advice. “The body is essentially in an overreaction mode because it views a certain food as a toxin. Intolerances are not life-threatening, but can still be problematic. In some cases, the body does not produce enough of the enzyme to break down a certain food, or the villi lining the small intestine can become inflamed, which causes the distressing symptoms like gas, diarrhoea and bloating.” When that happens in the middle of a race, chances are you’re going to be stopping for the bathroom.

But recognising a food intolerance is half the battle. Once you identify it, you can start to fuel your body in ways that won’t give you trouble. Here are the most common food intolerances and some tried-and-true methods for beating them.


Photo: Timmary/Shutterstock


Gluten is the protein in grains that helps bind together runner staples like breads, bagels, pastas and oats. Gluten-free versions of all these foods are readily available, but that doesn’t necessarily mean you should just trade in all your favourite foods for their gluten-free versions. If you have a gluten intolerance, Bonci recommends finding swaps for certain foods – like trying zucchini noodles in place of pasta – and using gluten-free versions as needed because GF versions can be more expensive. Plus, a discriminating palate will usually be able to tell the difference. And when you remove the gluten from certain foods, you can also lose some of the protein. To sidestep this issue, Bonci suggests carb sources that are naturally gluten-free – like rice, potatoes, millet and quinoa – and reaching for corn, rice, and even bean-based pastas and cereals based on personal preference.

Whether you have an allergy, intolerance, or sensitivity to gluten will also play a role in what ends up in your shopping trolley. Individuals with coeliac disease, an autoimmune disorder, need to eliminate gluten from their diets entirely because it causes damage to the small intestines. Gluten is off the table, period. But if someone is intolerant, they may have some wiggle room. “If someone has a gluten intolerance, they can experience digestive problems, but there is no damage to the intestine,” Bonci says. They may choose to cut out it out entirely, or limit their consumption based on what they can tolerate. The third possibility is a non-coeliac wheat sensitivity. In this case, individuals can have any glutinous foods – like rye, barley, and oats – but not wheat. Depending on their symptoms, individuals may scale back on wheat or nix it all together.

2 Dairy

Photo: margouillat photo/Shutterstock


After gluten, dairy is the second most common culprit for digestive issues among runners. Lactose, the naturally occurring sugar in dairy products, falls under the “D” in the FODMAP acronym – Fermentable Oligo-,Di-, Mono-saccharides, and Polyols. FODMAPs are poorly absorbed short chain carbohydrates, which means that they pull extra water into the small intestines during digestion, which can then cause issues like bloating, gas, diarrhoea and constipation. A high-FODMAP food is more likely to cause these problems.

Sidestepping a lactose intolerance can be as easy as taking a lactase pill or drops, which contain the enzyme responsible for breaking down the sugar. Or, lactose-free versions of most dairy products are an easy and inexpensive swap. Plus, many people with a lactose-intolerance can still tolerate many yoghurts due to its live and active cultures and aged cheeses that are naturally low in lactose. However, Bonci does caution runners from switching over to plant-based products (like almond and coconut milks) entirely. “The majority of plant-based milks are pretty low in protein, with the exception of pea, peanut and soy,” she says. “Nutritionally, they just don’t compare to dairy milk, and they also come at a higher price point.”

3 Fructose

Photo: leonori/Shutterstock


Believe it or not, the simple sugar found in fruits and vegetables is also a FODMAP. Runners who opt for a pre-run apple or watermelon slice, which are especially high in fructose, may be surprised to find them as the cause of their digestive problems. Bananas, clementines, oranges, strawberries and even papaya are safer options before a morning run.

But even small things like swapping sugar for a drizzle of honey or agave in your morning oatmeal can derail digestion a few kilometres down the road. While these natural sugars provide a quick punch of energy, they are high in fructose. Bonci recommends maple syrup or stevia instead if you’re finicky to fruit sugars.

In situations like these, in which runners are blindsided by what’s causing an upset, many think they simply can’t tolerate food before a run and just skip their pre-run meal. This is almost always the wrong move. Bonci says this is why finding the right substitutes for problematic foods becomes especially important.

“The big thing that I aways talk to my runners about is it’s not just what you take off the plate, it’s what you put there instead,” she says. “Runners need to be fuelled, and we don’t want them running on empty.”

4 Yeast

Photo: Fascinadora/Shutterstock


These tiny fungi help bread rise, so they’ll crop up in the obvious places like bagels, rolls and muffins. But you’ll also find them in your post-race beer. This doesn’t mean you need to cut out your favourite pint but adjust based on your symptoms.

“A lot of food sensitivities are volume-related,” says Bonci. “So when people work on changing the amount of a problem food rather than cutting it out entirely, they have a much broader base of foods to choose from. It’s so much nicer to be able to include the foods that you like rather than live in the ‘Land of No’ all the time.”

Avoiding yeast can be as simple as checking ingredient labels, or opting for an unleavened alternative. Pitas, tortillas, crackers, and pasta are great carb sources without yeast (but you will have to double-check for gluten if that also bothers you). Rice-based crackers and cereals are also good options.

5 Eggs

Photo: siambizkit/Shutterstock


The protein found in the egg yolk and white is a common allergy and can be one of the reasons your runs aren’t turning sunny-side up. Eggs may be in foods you least expect.”It really requires being hyper-vigilant about label-reading,” says Bonci. When you’re looking for a post-long run treat, an easy way to skip the egg is to look for items labeled ‘vegan’.


Photo: StudioByTheSea/Shutterstock


That cup of coffee gets you moving on race morning in more ways than one. But when it comes to caffeine-related digestive distress, Bonci says there are a few things to consider. Be aware of how much you consume, and if you do get your caffeine kick from coffee, be wary of what you are mixing in. For example, if you’re adding milk or an alcohol-based sweetener (like erythritol), those could be the culprit rather than the caffeine. Waiting a few minutes to run after you drink your cup of joe can let your stomach settle and give you some time to fit in a bathroom break.

However, some individuals do have a hypersensitivity to caffeine, which can cause headaches, racing heartbeat and nervousness (above and beyond the usual pre-race jitters). If you count yourself among the caffeine-sensitive – or you just prefer decaf–sipping on any hot beverage can have a laxative effect to get your system moving in the morning without the added stress.

7 Sugar Alcohols

Photo: SpeedKingz/Shutterstock


Runners frequently turn to these artificial sweeteners when looking to shave kilojoules or sugar from their diets. Another type of FODMAP, sugar alcohols can show up in nearly any food product labelled ‘sugar-free’ or ‘no added sugar’, so you’ll need to check the ingredient list. Xylitol, mannitol, and erythritol are just a few aliases to look out for. Sugar-free gum and mints can be especially high in this category, so steer clear if you know you’re sensitive. And if you really need a low-kilojoule sweetener, try plant-based stevia.

While food intolerances can be irritating, they don’t have to sabotage your race. Some extra vigilance and a few tweaks to your diet can get you from start to finish line confidently, knowing there won’t be any unwelcome stops in-between.

“Everybody keeps a log of their mileage, so if you’re having digestive issues, keep a log of your foods and symptoms,” Bonci suggests. “That’s how you can be your own detective and determine what works and what doesn’t.”

Subscribe to Runner's World

Related Articles