Episode 6 - 7 Tips to Manage Runners Gut

7 Tips to Manage Runners Gut

Are you the type of runner that knows exactly where every public toilet is along your route?

Don’t worry - you are not alone! 30-50% of athletes regularly suffer from gastrointestinal (GI) problems while exercising.

Far too common among endurance athletes, GI symptoms include nausea, cramps, bloating, wind, vomiting, diarrhoea and urgency. It seems that the frequency, intensity and severity of these symptoms increases as the event distance increases.

So why exactly does it happen? And what can you do to prevent runners gut?

In this episode you will learn:

  1. What causes runners gut?

  2. My top tips for preventing runners gut


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  1.   de Oliviera EP, Burini RC. Food-dependent, exercise-induced gastrointestinal distress. Journal of the International Society of Sports Nutrition. 2011; 8: p12.
  2.   de Oliviera EP, Burini RC. Carbohydrate-Dependent, Exercise-Induced Gastrointestinal Distress. Nutrients. 2014; 6: 4191-4199.
  3.   Pfeiffer B et al. Nutritional Intake and Gastrointestinal Problems during Competitive Endurance Events. Medicine & Science in Sports & Exercise. 2012; 44(2): p344-351.
  4.   Sessions J et al. Carbohydrate gel ingestion during running in the heat on markers of gastrointestinal distress. European Journal of Sport Science. 2016; 16(8): p1064-1072.
  5.   Hansen EA et al. Improved Marathon Performance by In-Race Nutritional Strategy Intervention. International Journal Sport Nutrition and Exercise Metabolism. 2014; 24: p645-655.
  6.   Cox GR, Clark SA, Amanda J. Cox AJ, Halson SL, Hargreaves M, Hawley JA, Jeacocke N, Snow RJ, Yeo WK, Burke LM. Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling. Journal of Applied Physiology. 2010 109(1); p126-134 DOI: 10.1152/japplphysiol.00950.2009
  7.   Lambert GP, Lang J, Bull A, et al. Fluid tolerance while running: effect of repeated trials. International Journal of Sports Medicine. 2008; 29: p878–82.
  8.   Cunningham KM, Horowitz M, Read NW. The effect of short-term dietary supplementation with glucose on gastric emptying in humans. British Journal of Nutrition. 1991; 65: (15–9).
  9.   de Oliveira, E. P., Burini, R. C., Jeukendrup, A. 2014. Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations. Sports Medicine 44 Suppl 1: S79-85.

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Episode Transcription

EP 6 – 7 Tips to Manage Runners Gut

Are you the type of runner that knows exactly where every public toilet is along your route? Or do you know that you've got maybe 7km’s before you know you’ll need to find the loo on every run? Don't worry, you are not alone. 30% to 50% of athletes regularly suffer from gut upset while exercising. It can be totally frustrating and a point of stress.  And sometimes that stress can make it worse. It's really common amongst endurance athletes. So gut symptoms like nausea, cramps, bloating, wind, worst-case scenario – vomiting and diarrhoea. And maybe even like Dire Straits is like that urgency where you've got to get to a toilet now and you're not sure you're going to make it.

So today I wanted to share with you some tips to prevent runners gut. So you can start to tackle some of the nutritional issues that might be playing a part in the symptoms that you're experiencing. I want to give you the confidence back that you can run wherever you want without having to try and plan your routes based on toilet availability. You want to be able to run with a friend and not be embarrassed about having to stop all the time. And finally piece together a run longer than maybe 7km’s without having to stop.

It seems that the frequency, the intensity and the severity of those symptoms increases as your event distance increases. It may be worse for Ironman athletes who are doing much longer training sessions compared to somebody that might be just doing Sprint and Olympic distance triathlon where your sessions are much shorter in comparison.

So why exactly does runners gut happen?

Well, it's multifaceted and highly individual. But some of the reasons could be that it's mechanical or physiological or it could also be nutritional. We also know that the symptoms are exacerbated or made worse by dehydration and hot weather conditions. If you're a female, you're younger and you run at high intensities, you may be at high risk of gut upset too, damn it!

Running causes an increase in intra-abdominal pressure. Which when combined with our organs bouncing up and down, that can cause gut symptoms. So when we exercise, blood flow is redirected away from our gastrointestinal tract to the exercising muscles. Our heart, our lungs, our diaphragm, so we can breathe our brain and our skin for cooling. Blood flow to our intestines, our digestive organs can be reduced by as much as like 80%, which is crazy. And that obviously compromises your gut function and can exacerbate symptoms.

Hydration also plays a really important role. Dehydrated athletes, they've reported higher rates of nausea, abdominal cramping and delayed gastric emptying. So that's the rate that food leaves your stomach. And I guess nausea associated with that when you've got food stuck in your gut and it's not going anywhere. Combine that with decreased blood flow to the gut with dehydration and it can cause increased permeability of the gut. So in plain English, things are moving across the gut walls in a way that they shouldn't be causing gut upset. From a nutritional point of view, things like fat, fibre, protein and high carbohydrate concentration, so osmolarity, they can all be associated with increased risk of gut symptoms. Fat, fibre and protein, they all slow down digestion. So it's definitely not ideal to be consuming those things when you're running at pace. And we know that large amounts of carbohydrate may not be fully absorbed across the gut wall. And that leaves residual carbohydrate in the stomach. That obviously causes symptoms during exercise like bloating and fullness and nausea. And worst-case scenario, if you're properly pushing the pace, the only way is out.

So what can you do to prevent runners gut?

Here are a few tips:

  1. Train your gut
    The gut is extremely adaptable. Research in human shows that you can train you gut in as little as about 30 days to increase your absorption capacity. That's pretty cool. So you want to train you gut just as you would train your muscles to absorb nutrition while you're exercising. Start small and slowly Increase the quantities of food or fluids or both that you consume while you're running. But do it over a few weeks to months to build your tolerance up.

    You also want to try different types of foods or liquids or gels in training to figure out what works best for you. The Golden Rule of sports nutrition – Never try anything new on race day. So many clients I've seen, before they've come to see me, they wing it with every race with a completely different strategy based on how they’re feeling on the day or what's available or what's on course. You should be practising what you plan to race with in training for months before the big dance.

    Keep in mind though, that gut symptoms are usually increased with distance, heat and humidity. So you'll likely need different strategies depending on the season, whether it's winter or summer and the distance that you're running.

  2. Play with different carbohydrate sources
    So we know our gut absorption rate of glucose alone, that maxes out at about 1g a minute or 60g of carbs an hour. For the longer endurance events though, say greater than two hours, like a half and a full marathon or any 50k runners or 100k runners and ultra runners out there. You probably need more carbohydrate than that anyway. So you can increase your carbohydrate absorption capacity by utilising different carbohydrates.

    So things like glucose and fructose. Because we know they're absorbed across the gut wall via different pathways. So glucose can occur simultaneously to fructose absorption. Again, like anything, you want to stick to smaller amounts and build your tolerance up over several weeks to months.

  3. Avoid high fibre foods right before competition
    Might be intuitive but the number of people I've seen that don't do this is insane. So in the day or two heading into hard training or competition, you might want to look at decreasing your fibre intake to minimise the amount of undigested fibre that's left in your gut. So not my usual advice to you as a dietitian, but from a gut perspective, you might want to look at choosing things like more white refined breads and cereals instead of wholemeal and whole-grain or the really dense ones. And keep high fibre veggies and fruits to a minimum as well.

    So it doesn't mean you have to cut them out altogether. Some low fibre options could be tomato, or zucchini, olives, grapes, grapefruit, all of them have less than a gram of fibre per serve. So obviously, this is not a long term approach. I'd only do it for a day maybe two ahead of a big competition. But generally, you should be consuming a really high fibre diet to regulate your bowel movements and keep you regular and keep your gut microbes happy.

  4. Go easy on the coffee
    If you have a sensitive gut, I’d probably look at avoiding drinking coffee on an empty stomach or right before hard runs. I know I know, coffee is the best and you know it does have performance-enhancing effects. But coffee is a really strong gut irritation and could be exacerbating your problems. So save your brew for post-exercise. There are plenty of other ways to get caffeine in so don't stress.

  5. Start exercise hydrated and make sure you stay hydrated
    It goes without saying right? But the number of athletes I see turn up to sweat testing already dehydrated is insane. Without the use of regular USG. So the Urine Specific Gravity that I test, you can just monitor the colour of your urine. And that can give you a good general idea of your hydration status. So you're aiming for pale straw coloured urine on a day to day basis as a good measure of hydration. If it's crystal clear, you're overdoing it. It's just pouring out through your kidneys and you're not doing a great job of retention. And if it's really dark, then you probably need to drink more.

    During exercise, you typically need to drink to replace your sweat losses enough, right? Because you don't want to put yourself into the red of dehydration where performance is affected. So I'd suggest doing some sweat testing to figure out what your sweat rate actually is and do it across different environmental conditions. So you want to have an understanding of how you sweat in the height of summer where it's crazy hot. And you also want to have an understanding of how you sweat through the winter months where it's much cooler. You don't want to have a strategy, like anything, that is just the same across the year. You need to have some structure and some purpose to what you're doing.

Now how much fluid you replace to minimise sweat losses is highly individual. It depends on how heavy a sweater you are. So somebody that sweats 3L an hour is obviously going to dehydrate much faster, if they're not keeping pace with that than somebody that only sweats 500mls an hour. So depending on who you are, you might want to replace maybe 50% of your sweat losses, some people need to replace up to 80% of their sweat losses, depending on the conditions and I guess the duration and the intensity are important for that as well.

Again, something to practice. If your sweat rate is you know, greater than 3L an hour, you will struggle to drink and absorb this volume of fluid without some serious gut training. And you know, you may never get there either, it may not physically be possible to keep pace with that loss over a long run.

Another good tip then, is to have a good hit of water with your pre-exercise meal. So somewhere in the realms of 300 to 400 mls maybe depends on who you are and what size you are, as that's going to prime the stomach to empty and then you're absorbing your nutrition so that you can use it during exercise too. So again, something to practice. Start with a small volume, say 100ml to 200mls with the pre-exercise meal, and then build that up to say 350-400 mls plus, depending on, again it depends on how big you are. A couple of hours before exercise. So a sports dietitian can help you with an individualised hydration plan to map that out for you.

Let me know if this sounds like you. Do you feel exhausted by the end of the training week? Do you crave sweets in the afternoon and feel like you need a nap? Training for 3 disciplines can be absolutely exhausting if you haven't dialled in your nutrition. It can be frustrating when you can't quite piece together the solid race performance you know you're capable of. And confusing when there's so much information out there. But you're not sure what's the right method for you.

My goal for you is to unlock your true potential and feel like a supercharged triathlete. Firing on all cylinders, full of energy and not only smashing quality training sessions, performing in every race too. If you're finally ready to start nailing your nutrition, join a powerful community of like-minded athletes in the Triathlon Nutrition Academy program. Head to www.dietitianapproved.com/academy to check it out now. For less than the cost of a coffee a day, you will finally have a plan for your nutrition instead of winging it and hoping for the best.


  1. Your day to day diet is going to impact your ability to absorb nutrients while you're running
    So we know based on research that increased gastric emptying of carbohydrate, so the food leaving your stomach and going further along the digestive tract, that’s increased by daily dietary carbohydrate. So if you eat more carbohydrate, you're better at absorbing it. But interestingly, having a really high fat intake results in faster gastric emptying of fat, but not carbohydrate. How cool is that?

    So if you generally have a high carbohydrate diet, that increases your ability to absorb carbohydrate across the intestinal wall which in turn, allows for greater absorption and then oxidation of carbohydrate during exercise. So that's going to lower the chance of gut distress. So for those people that follow a low carb, high-fat diet generally, your intestines respond by decreasing intestinal absorption of carbohydrate and increasing fat absorption. So if you then go try and ramp up your carbohydrate intake just before competition or do low carb, high fat and then have a whole heap of carbohydrate in your event, it makes no sense because chances are you're not going to absorb that very well and you have a higher chance of running into GI issues on race day – pun intended.

    It's also unlikely you'll be able to increase your carbohydrate intake beyond the 60g per hour, if that isn't something you've practised in training. Your gut is trainable. But unless you're throwing the stimulus at it, it's not going to then train itself just like you can't sit on the couch and expect to run a marathon, you have to go out and do the training, your gut is the same. So ideal scenario is you periodise your intake across the week. So you have some days of high carbohydrate availability. And some days maybe with low carbohydrate availability, depending on what your goals are and your events are.
  2. Take a look at the low fodmap test diet
    A lot of runners gut issues can be just what's going on in your day to day nutrition and that wreaking havoc. And it's not until you run that you get that increased jiggling of your stomach, plus the low gut perfusion of blood, that it stimulates peristalsis, which is that muscular movement of your gastrointestinal tract. It just moves things through quicker. So if your day to day diet is full of foods that you don't particularly digest well or break down well anyway, throw the stress of running at it and it's obviously going to exacerbate that further.

    So have a look at implementing that with a sports dietitian or a general dietitian can do this as well, if that's something that could be a problem for you. So I'm going to run through a couple of foods. And if you're the type of person that naturally avoids them because either you don't feel like you like them, maybe it's something you need to explore further, because they could just be foods that you don't digest and tolerate well.

So a couple of big ones are onion and garlic, apples and pears, mushrooms, cauliflower, normal breads or pastas, fruit juice, dried fruit, milk or yoghurt, or really high lactose type foods. If any of those foods are in the back of your mind going “Yep, I definitely avoid those because I'd know that they're giving me issues” then there may be some benefit to going through a FODMAP test diet with a dietitian.

Now, please don't pull this from the internet. This is exactly why I started this podcast that you stop doing that. The FODMAP diet is a test diet and it only should be followed for two, maximum four weeks. And the premise is that you remove all the foods that can be an issue for you. And then you systematically reintroduce each group back in and figure out what the problem is.

Now, it's not something to do on your own, you definitely need to do it with a dietitian that is qualified and experienced in this space because you can F it up. And we know that the longer you pull these foods out of your diet, the more you actually affect your gut microbiota. The bugs that are in your gastrointestinal tract. And they can have other long term health implications.

So please don't mess with it. Because I've seen so many people that get put on it by somebody that doesn't know what they're doing. Or their GP says go and do this here's a sheet and then they're on it forever. And they have no idea how to reintroduce foods back in. And the problem is that it just might be one, maybe two groups of foods that could be a problem for you. It's not all of them. But you've been avoiding all of them unnecessarily. So your diet is limited and restricted. And that's not fun. So you lose all that good variety in your diet too. So definitely make sure if you're in the back of your mind, you're thinking this resonates with me and this is potentially me, do it with somebody that's qualified to do it and be systematic in your approach so you can get on it and then get off it quickly.

So that's my seven tips for trying to deal with runners gut. If something in there has resonated with you then definitely try and get to the bottom of it. A lot of runners gut symptoms are preventable, but there's no point just trying to wing it on your own. It's a really generally easy, quick fix. But you just need somebody that knows what they're doing to help you with it and get to the bottom of it really quickly because it sucks trying to run and needing to know where every toilet is on your route. Or also knowing that you've only got to 6km's before you're going to need to go and stop and go to the toilet.

Try and imagine a world where maybe you could run with others. Or you could get 10km to 15km's through without needing to go to the toilet. How good would that be? You could run longer, you could run better, you could run faster, and you could not have to use those disgusting portaloos in races. Ah, It'd be amazing!

So definitely get to the bottom of it. If runners gut is a problem for you stop trying to wing it yourself and actually get some strategy to what you're doing.

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