From ‘runner’s trots’ and nausea to painful cramping, digestive problems can derail even the best-planned run. Sports nutritionist and endurance runner Stephanie Jaczniakowska-McGirr explains how to fuel effectively without upsetting your stomach.
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Words: Stephanie Jaczniakowska-McGirr
If you’ve ever planned a long run around the location of the nearest public toilet, you’re definitely not alone. Gastrointestinal issues are incredibly common among runners, with some estimates suggesting that up to 90 per cent of distance runners have experienced GI distress during a race.
Years after Swedish distance runner Mikael Ekvall famously had to relieve himself during a half-marathon, photographs of the unfortunate incident still appear as viral memes on social media. So, let’s talk about how you can reduce your chances of finding yourself in a similar situation.
What causes ‘runner’s trots’?
There isn’t one single cause of runner’s stomach. Several different factors can combine to create digestive discomfort.
When you run, your body prioritises sending blood to the working muscles in your legs, which reduces blood flow to the digestive system. Add the physical jostling of running, dehydration, heat, race-day nerves and whatever you’ve chosen to eat before or during your run, and you can create the perfect storm for stomach problems.
While you can’t necessarily control changes in blood flow or the mechanical stress placed on your gut, you do have some control over how you fuel.
Why runners need carbohydrates
During endurance exercise, your body needs carbohydrates to provide energy because its carbohydrate stores – known as glycogen – are limited.
Consuming between 60g and 90g of carbohydrate per hour is often recommended for prolonged endurance exercise. However, suddenly taking on large quantities of carbohydrate while your digestive system is already under stress can contribute to bloating, cramping, nausea or diarrhoea.
That doesn’t mean runners have to choose between fuelling properly and having a comfortable stomach. The type and quantity of carbohydrate you consume – as well as how accustomed your body is to taking in fuel while running – can make a significant difference.
Why the type of carbohydrate matters
I often hear runners say that energy gels make them feel sick or give them stomach cramps. If you’ve experienced this, the first things to consider are the type of carbohydrate in the gel and the total amount it contains.
Your intestine uses different transporters to absorb glucose and fructose. Combining the two in the same gel – often described as a dual-carbohydrate approach – can allow your body to absorb and use more carbohydrate than it would if you relied on glucose alone.
It may also reduce the amount of unabsorbed sugar sitting in the digestive system and contributing to discomfort.
A glucose-to-fructose ratio of around 1:0.8, as found in reeal gels, is increasingly used in endurance nutrition because it can support both carbohydrate availability and digestibility during prolonged exercise.
Could maltodextrin be upsetting your stomach?
Maltodextrin is a highly processed, plant-derived carbohydrate found in many conventional energy gels. It isn’t inherently bad and plenty of runners tolerate it well, but individual responses can vary.
Maltodextrin provides rapidly available energy, but some runners find that products containing it contribute to digestive discomfort. This may be because concentrated carbohydrates can draw water into the intestine, particularly when consumed without enough fluid.
If you regularly experience problems after using a particular gel, experiment with a different carbohydrate source during training. Some runners find gels made using real-food ingredients and natural sugar sources easier to tolerate.
Reeal gels, for example, use ingredients including brown rice syrup to provide the quick energy needed during endurance exercise while offering an alternative to more conventional gel formulas.
Check the sweeteners in your gel
It’s worth looking beyond the carbohydrate content and checking everything else in your chosen fuel.
Some gels contain artificial sweeteners to improve the flavour without adding more sugar. Certain sweeteners are poorly absorbed by the stomach and may cause cramping, bloating or excess gas in some people.
This doesn’t mean every runner needs to avoid sweeteners. However, if you repeatedly experience digestive problems during training, check the ingredients in your gels and experiment with an alternative that uses a different source of sweetness.
The important thing is to test any change during training rather than waiting until race day.
Be careful with caffeine
Caffeine can also be found in some energy gels. I enjoy a cup of coffee as much as the next person, and there is compelling evidence that caffeine can support endurance performance and reduce how difficult exercise feels.
However, consuming too much caffeine – or taking it at the wrong time – may cause digestive discomfort. Caffeine can stimulate bowel movements, which isn’t necessarily what you want midway through a race.
Consider consuming your usual caffeine around an hour before running and using non-caffeinated gels during the race. During a marathon, you might choose to introduce some caffeine later in the event if you know from training that you tolerate it well.
How people respond to caffeine varies considerably, so always practise your strategy before race day.
How to train your gut
Perhaps the most important step is training your digestive system to tolerate fuel while you run.
You’ve probably heard the age-old advice, ‘Nothing new on race day.’ This is especially important when it comes to nutrition. Rather than saving your energy gels for the event itself, practise your fuelling strategy throughout your training block.
If you’re new to endurance running, start with a manageable amount – perhaps around 30g of carbohydrate per hour during your longer runs. You can then increase this gradually from week to week as your body adapts and your training demands grow.
Depending on the length and intensity of the event, you may eventually aim for between 60g and 90g per hour. The number of gels required will depend on how much carbohydrate each one contains, so always check the label rather than assuming every gel provides the same amount.
Regularly consuming carbohydrates while running helps your digestive system become accustomed to handling fuel while your body is working hard.
You could choose a product that appears perfect on paper, but if the first time you use it is during your race, you may still experience digestive problems.
Why enjoying your fuel matters
One estimate suggests that a runner may consume around 57 gels during a marathon training block. If you dread every single one, it’s going to be a pretty unpleasant few months.
You may start avoiding fuel during training, which could leave you underprepared and at greater risk of hitting the wall – or making an emergency dash for the toilet – during your race.
This is why enjoying your fuel matters so much to me.
I created reeal because I couldn’t find a gel I liked while training for my first marathon. I found many of them too sweet, some textures made me gag and long lists of unfamiliar ingredients put me off.
I began making my own gels in my kitchen and carrying them on runs in reusable baby-food pouches. Those homemade gels eventually fuelled me through a marathon, a 50km race and a 100km race, and became the starting point for reeal.
Today, reeal gels are made with nine real-food ingredients, contain no artificial additives and have a smooth, purée-like texture. Some runners have even compared the tropical flavour to a Solero.
I’m obviously biased because reeal is everything I wanted from an energy gel. But the truth is that there isn’t one perfect product or fuelling strategy for every runner.
The goal is to find something you enjoy, can tolerate and are able to consume consistently when your body is working hard. You can do difficult things – but fuelling your run shouldn’t have to be one of them.
Stephanie Jaczniakowska-McGirr is an everyday endurance runner, qualified sport and performance nutritionist and founder of reeal, the real-food energy gel brand she created after struggling to find fuel she could enjoy and tolerate while training for her first marathon.
