What is Runners Gut?

What is Runners Gut?

Runner’s gut and how to avoid it during exercise:


What is a runner's gut?


Picture this, it is the morning of your big race or walk and you are sipping away at your coffee, running through the plan of attack for the event. After eating a solid breakfast and much needed caffeine boost, it’s time to get ready and head off to the fun run. As you arrive, kitted out with all of your ‘Clothing The Gaps’ merch, strapping of knees, ankles, feet and the like perfected, it’s time to start warming up. Nerves might be kicking in at this point, often where you can begin to feel your stomach grumbling and gut discomfort. Especially, if there hasn’t been a post coffee bowel motion in the morning. As the race begins, setting your pace and moving through the distance of your run/walk, each step is bouncing your internal organs, making an undesirable milkshake of your previously consumed food and fluid. The race continues, as does your growing urgency to find a bathroom and it’s becoming a real pain in the…you get it. Your choices are now to either stop at the next toilet you lock eyes with, disturbing your pursuit or to push through, hoping your gut is well trained to retain its contents on demand.

This is an example of how ‘runner's gut’ can show up. A very unwelcome guest. 

When exercising, your blood flow is directed away from your gut and towards the working muscles, such as your arms and legs (1). As a result, this decreases the function of your gut, increases sensitivity and risks symptoms including;

  •  Diarrhea, 
  • Gas/Flatulence
  •  Cramps/Feeling of a ‘stitch’
  •  Nausea and vomiting 


What can you do to prevent this from occurring?

Keeping well hydrated:

Commencing exercise in a dehydrated state can have a significant impact on gut function and increases the risk of unpleasant symptoms listed above. Additionally, contributing to headaches, lack of concentration, dizziness and tiredness. Certainly, not a great time while trying to compete in your event (2).

As described in the previous blog see here there are general recommendations of your individual requirements of fluid and electrolytes. 

Depending on the length of your event and your sweat rate (how much you sweat in an hour), will determine your needs for hydration before, during and after your event. 

In addition to the fluid and salt requirements previously discussed, being aware of the volume of water in your stomach pre-exercise and during it essential in helping minimise gut upset.

Keeping up a consistent fluid intake in the days and hours leading up to your event is important for prevention of drinking large volumes close to the start time. If choosing to drink fluids in the last minutes prior to your event, a maximum of 300-400ml is recommended. This is a volume reported to be tolerated well, however, trialing this during your training in the weeks leading up will help you determine what works best for your body (2). Another trick is to consume smaller volumes throughout the race with a well-planned hydration goal (particularly for longer events over 60-90minutes) (1).  

If choosing a sports drink either pre-event or during, aiming for a carbohydrate concentration of between 4-8g/100ml can assist in less gut disturbances. Highly concentrated drinks like juices and cordials, full fat milk or caffeinated beverages consumed closely before or during exercise have been reported to cause runner’s gut symptoms (1).  



Avoid triggering foods on race day:  

Understanding your gastric emptying process (how fast your stomach releases food and fluid into the small intestines) is the key in mapping out your eating on race day to avoid gut discomfort (3). 

When planning the meals and timing of your nutrition, here are a few gut loving things to take into consideration; 

  • High fibre, high fat and high protein meals and snacks are slower to digest and create a sensation of heaviness if eaten too closely to the event. The last meal should be consumed 1-4 hours before to allow time for digestion (1,3).
  • If choosing to eat closer to the event, aim for low fibre options such as white bread, crumpets, low fat dairy and smoothies (1). 
  • If you have any pre-existing conditions avoid trigger foods in the days leading up and seek advice from a medical professional. 

Glucose gel for longer distance events: 

  • Keep in mind that the highly concentrated glucose/fructose gels can be problematic for some people. General recommendation is 60g/hour is better tolerated than 90g/hour (1). 
  • It is really important to practice including these gels in the weeks of training leading up to your event, this will help to “train” your gut and gain an understanding of your body's limitations. Working closely with a sports Dietitian or Nutritionist is a great support in working out individual needs. 

Managing stress/anxiety: 


Pre-event nerves can wreak havoc on the gut (and mindset). Practicing calming and mindful activities prior can assist in reducing unwanted bowel disturbances (4). 


Here are a few strategies; 

  • Breathing techniques - deep breaths increasing the inhale and exhale, as often our breathing becomes short and sharp when we are nervous. 
  • Meditation - using guided meditation apps to help you relax 
  • Having a plan if you do really need to find a toilet, ask organisers where the bathrooms will be along the course. 
  • Running/walking pal or team that is supportive and can talk with you about how you are feeling and what your plan for the event is. 


Seek professional medical and health support for pre-existing gut health conditions including: 

  • Irritable bowel syndrome (IBS)
  • Celiac disease 
  • Irritable bowel disease 
  • Other food allergies/Intolerance 




  1. Burke, L., Deakin, V., & Allanson, B. (2015). Clinical sports nutrition. Mcgraw-Hill Education (Australia) Pty Ltd.

  1. Silver, R et al (2010) Pre-exercise Urine Specific Gravity and Fluid Intake During One-Hour Running in a Thermoneutral Environment – A Randomized Cross-Over Study. Journal of Sports Science & Medicine. 

  1. De Oliveira, E.P et al (2014) Gastrointestinal Complaints During Exercise: Prevalence, Etiology and Nutritional Recommendations. Sports Medicine 44, 79-85


  1. Wilson, P (2017) Perceived life stress and anxiety correlate with chronic gastrointestinal symptoms in runners. Journal of Sports Sciences.



Emily Rault – Accredited Practising Dietitian

Website – https://www.freshstartforlife.com.au/

Instagram - https://www.instagram.com/emrault/





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