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Runner’s tummy: what to do if you get the runs on a run

11th October, 2023

So why do runners get tummy troubles?

Ever had tummy troubles during or after a run? If you’re a runner, you may have experienced the dreaded “runnner’s stomach” – the uncomfortable and sometimes painful digestive issues that can pop up during or after a run.

Whether it’s cramps, bloating, diarrhoea, or nausea, a troublesome tummy can be frustrating and disrupt your exercise routine. If you’ve felt the effects, you’re not alone. It’s estimated to affect up to a whopping 90% of runners.

There are several reasons for these symptoms – as well as the physical jostling itself, it can often be down to your body diverting the blood flow away from your digestion to where your muscles need it most. This can lead to a more permeable or “leaky” gut.

If you’re not properly hydrated, this can also contribute to constipation and cramping, while fuelling with high-fibre or high-fat foods too close to a run can give you some digestive discomfort. Stress can also be a factor, and if you have any existing tummy troubles like IBS, running can be a trigger.

Is it IBS?

One study investigated tummy troubles among 430 endurance athletes (think marathons and triathlons) and found that over 56% of the athletes experienced at least one gut symptom during training or during a competition.

While only 2.8% of them had been diagnosed with irritable bowel syndrome (IBS), the researchers found that actually 9.8% of them met the criteria for IBS. This shows that most athletes who suffer from IBS haven’t been diagnosed, and even more experience troublesome tummy symptoms.

The take-home message: if you’re experiencing symptoms, it could be well worth looking into IBS and trying out our top tips.

How to reduce the runs while running

The good news is there are several things you can try to keep your tummy happy while you’re pounding the pavement:

1. Drink up

Drink plenty of fluids before, during, and after your run to avoid dehydration. When you’re dehydrated, your body tries to save its water by taking it away from your tummy. And this can lead to gut symptoms. For a long run, aim to drink enough water regularly (without downing it too quickly!) and take your time to figure out the right amount of fluid for you.

2. Mind your meals

High-fibre and high-fat foods can take longer to digest, so try avoiding these just before a run. Instead, go for easy-to-digest carbs like toast or a banana.

What about FODMAPs?

FODMAPs are types of carbs that are highly fermented in your tummy (you can read more about those here). Some initial studies suggest avoiding high-FODMAP foods in the short-term before a run can help you reduce the risk of runner’s tum. So it might be worth missing out on FODMAP foods like garlic, onion and beans temporarily. Just remember to reintroduce those tummy-loving foods afterwards!

3. Test the timing

Some runners find running in the morning on an empty stomach is easy on their tummies, but others find a small snack before running helps. Experiment to see what suits you. For most of us, giving your tummy time to digest your food by eating at least 2-3 hours before going for a run is a good idea.

4. Watch the caffeine

It might seem like a good idea to down a caffeinated energy drink right before the off, but caffeine stimulates your gut to move, which might cause a sudden need to go, after you go! Instead, opt for smaller, more regular hits of caffeine throughout the race or try getting your caffeine from matcha, which reduces some of the side effects of caffeine due to the presence of l-theanine.

5. Make time for mindfulness

Feeling the pre-race nerves? Stress can have a big impact on your tummy and can trigger trouble like bloating, nausea and diarrhoea. You might even notice that you need to use the toilet more frequently before a big race! Try practicing stress-busting techniques like deep breathing, meditation, or yoga to calm those nerves for peak performance and a happy gut.

Want to know what supplements can help runner’s tummy?

Leaky gut and long-distance running

Studies have shown that endurance exercise causes the gut lining to become more permeable or “leaky”. This means things can escape from the gut into the blood, such as food antigens and bacterial toxins.

A leaky gut is more common when running for over 1 hour and running in hotter temperatures. It appears to happen because blood is directed away from the gut during intense exercise to help muscles, so there is less oxygen supplied to the gut leading to ischemia. With less oxygen, the cells that normally keep the gut lining intact become damaged.

It’s also been shown that strenuous exercise affects the balance of microbes in the gut. This offset in the gut microbiota can also contribute to increased intestinal permeability and digestive symptoms like boating and diarrhoea.

Supplements for a runner’s tummy

We’ve already discussed some general tips to prevent digestive symptoms during your run like limiting fat and fibre beforehand, timing your meals effectively, and practicing mindfulness. But are there any supplements that can help too?

Probiotics

Probiotics are live microorganisms, usually bacteria or yeast, that when ingested give us some sort of health benefit. Probiotic supplements are often used to treat digestive symptoms, but they may also help to prevent them during exercise.

24 recreational runners training for a marathon were randomized into two groups. One group took a multi-strain probiotic (Lab4) and the other group took a placebo for 4 weeks before the race. The results: The group taking the Lab4 probiotic experienced less digestive symptoms during training and in the final third of the marathon.

STUDY SNAPSHOT

L-glutamine

L-glutamine is an amino acid that has been shown to help reduce intestinal permeability (leaky gut) in people with irritable bowel syndrome, but it may also help to prevent leaky gut caused by intense exercise.

10 recreational male runners completed four 60-minute runs at 30C. Prior to each run, they were given a placebo or glutamine. The results: L-glutamine helped to reduce leaky gut caused by running at high temperatures.

STUDY SNAPSHOT

Digestive enzymes

Carbohydrates are the preferred fuel source for exercise and running. However, fermentable carbohydrates known as FODMAPs can cause digestive issues in people with sensitive stomachs, especially bloating.

Fructose and fructans are a type of FODMAP found in foods like garlic, onions, apples, wholewheat and even energy gels. When running, these fermentable sugars move through our gut more quickly, escaping digestion, and arriving at our gut bacteria where they are fermented to produce gas.

Avoiding high FODMAP food before a race may be sensible, but digestive enzymes can also help to break down these carbohydrates making them easier to digest (and less likely to cause bloating). You can see our blog on digestive enzymes for more info.

Intestinal adsorbent

As we mentioned earlier, many runners who experience gut symptoms may have undiagnosed IBS. Bloating and diarrhoea are common digestive problems caused by endurance running, so people with IBS may be put off exercising due to the increased risk of experiencing these.

Intestinal adsorbents are supplements that move through your gut and help to mop up some of the excess gas and toxins produced by bacteria and food. One such intestinal adsorbent called Enterosgel has been shown to help treat diarrhoea in people with IBS-D.

Whilst there isn’t a study to show it helps to prevent diarrhoea during a run, it may be helpful for people with IBS-D who like to run recreationally but avoid it due to potentially needing the toilet during their run.

If you want to see which particular products may help, head to our reviews section.

Swot up on the science

Exercise and gut symptoms: running-induced changes. Karhu, et al. European Journal of Applied Physiology, 2017.
Dietary patterns in runners with gastrointestinal disorders. Erdman, et al. Nutrients, 2021.
Dietary restrictions in endurance runners to mitigate exercise-induced gut symptoms. Parnell, et al. Journal of the International Society of Sports Nutrition, 2020.
Four weeks of probiotic supplementation reduces GI symptoms during a marathon race. Pugh et al. Eur J App Nutrition. 2019.

Glutamine supplementation reduces markers of intestinal permeability during running in the heat in a dose-dependent manner. Pugh et al. Eur J App Nutrition. 2017
IBS is underdiagnosed among endurance athletes. Killian and Lee. Applied Physiology, Nutrition and Metabolism, 2019.
Is There an Exercise-Intensity Threshold Capable of Avoiding the Leaky Gut? Ribeiro et al. Frontiers Nutrition. 2021.
Short-term low FODMAP diet on exercise-related gut symptoms. Wiffin, et al. Journal of the International Society of Sports Nutrition, 2019.

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Runner’s tummy: what to do if you get the runs on a run

So why do runners get tummy troubles?

Is it IBS?

How to reduce the runs while running

Leaky gut and long-distance running

Supplements for a runner’s tummy

Probiotics

L-glutamine

Digestive enzymes

Intestinal adsorbent

Swot up on the science

RELATED ARTICLES

Want to be a part of the movement?

Let’s stay connected

So why do runners get tummy troubles?

Is it IBS?

How to reduce the runs while running

Leaky gut and long-distance running

Supplements for a runner’s tummy

Probiotics

L-glutamine

Digestive enzymes

Intestinal adsorbent

Got tummy pains and diarrhoea?

Let’s stay connected