Runner’s stomach: How to avoid stomach upset mid-run

Gut health has been having its moment, and for good reason. But if you’re someone who loves a good run, your gut might not always be loving you back. Enter: runner’s stomach. 

It’s that not-so-fun mix of tummy troubles that can hit mid-run. And while it’s usually nothing serious, it can mess with your stride. Here’s what you need to know, and how to keep your gut on your side.

What is a runner's stomach?

Runner’s stomach, also known as runner’s ‘trots’ or runner’s gut, is the name for gastrointestinal issues experienced during running. It can show up as anything from mild tummy grumbles and bloating, to stomach pain or that sudden, urgent need to find a bathroom.

The more scientific terminology for athletes in general who experience these sorts of issues is exercise-associated gastrointestinal symptoms (EIGS). Runner’s stomach is fairly common and can disrupt your run or even cause anxiety. While it’s usually nothing serious, it’s worth checking in with a doctor if symptoms are severe.

Why it happens during running

Why does running seem to trigger gut symptoms more than other sports, especially in endurance events like marathons?

It could be due to a few key factors: 

• The physical movement, or mechanical strain, of the gastrointestinal tract (GIT) when running
• The redistribution of blood flow from the GIT to the working muscles
• Changes in neurological and hormonal functions during running
• Feeling anxious and nervous, which are also common factors in gut disturbances

Longer duration events also require you to eat and drink during them and not everyone tolerates this well when exercising. Hot ambient conditions can also increase the chances of gastrointestinal upsets. The lower blood sugar levels and metabolic changes that occur during high intensity endurance exercise may also play a part, particularly with symptoms such as nausea.

Younger athletes are more likely to experience runner’s stomach than older athletes. This could be due to less ‘conditioning’ of the GIT compared to the older athlete, exercising at a higher intensity, or a greater risk of dehydration due to inexperience. 

How to avoid runner’s stomach

If we want to enjoy your run, then you’d want to avoid suffering from the symptoms of runner’s stomach. The strategies with the most consistent benefits include:

• Having some carbohydrate and protein or drinks before and during exercise, and lowering high fibre foods before your run
• Being mindful of caffeine. Caffeine can stimulate bowel actions in some people, so think about when you’re having coffee and how many ‘shots’.
• Aiming for normal hydration (known as euhydration), and not being not over hydrated or dehydrated.
• Lowering low FODMAP foods around running (FODMAP = fermentable oligo, di-, and mono-saccharides and polyols) in your diet and assess symptoms.
• Gut training to get used to having food and fluid in your stomach while exercising.

Let’s dive a little deeper into what these gut-friendly strategies actually look like in practice:

Choose lower fibre foods in the meal 2-4 hours pre-run if you are experiencing runner’s stomach symptoms. Also keep the fat content lower and protein moderate. Fat, fibre and protein can all slow the rate of digestion, leaving food in the stomach for longer which may ramp up those unpleasant gut symptoms. 

Practice and see what works for you before the run as some people won’t feel symptoms no matter what they eat, and others will be looking for the nearest toilet. It might be the time for white or wholemeal bread, rather than a heavy wholegrain, prior to the run. A low fat yoghurt or glass of milk or ripe banana might also work well.

Lowering the FODMAP containing foods in your diet is best done talking to an Accredited Sports Dietitian. You don’t want to unnecessarily restrict foods in your diet more than you need to. It might be about reducing these foods before runs and competitions and finding serving sizes that suit the gut. Some of these higher FODMAP foods are garlic, onions, wheat, honey, apples, pears, and mangos. Sports supplements such as gels and some sports drinks can be high in fructose and other FODMAP carbohydrates that might be poorly absorbed. 

Dehydration increases the risk of nausea and vomiting so start hydrated and practice sipping throughout your runs to avoid dehydration. Train your body to get used to having some fluid in your stomach. Drinks that are too high in sugar, 10% or more, (e.g. energy drinks, soft drink and fruit juice) wont be as quickly absorbed as sports drinks or water, so be cautious of having too much of these. As body temperature rises and dehydration kicks in, the blood flow to the gut reduces and this can increase the risk of nausea, vomiting and diarrhoea. So keep cool and well hydrated to reduce your risk.

Other strategies that may assist include avoiding over heating and using cooling strategies. Low carbohydrate and high-fat diets, probiotic supplementation, and some pharmaceuticals may have negative outcomes.  

When to speak to a doctor or sports dietitian

If your runner’s stomach symptoms are hindering your runs, then it is time to talk to your doctor and possibly a sports dietitian. People with irritable bowel syndrome, and those with lactose and fructose malabsorption are more likely to experience symptoms. People with Coeliac disease can also be more likely to experience GIT symptoms. If you have any of these, you may need some investigations by a doctor. An Accredited Sports Dietitian can also help you plan your food and fluid to minimise symptoms. 

The bottom line

Don’t let runner’s stomach stop you in your tracks. Try some of these strategies if you’re experiencing symptoms, and if they still persist then consult your doctor and an Accredited Sports Dietitian. It is important to keep you on the track, field or wherever you enjoy running!

Reviewed by the Healthylife Advisory Board September 2025