If you’re a triathlete, chances are you’ve experienced it: the dreaded runner’s gut. Maybe you know exactly where every public toilet is along your route, or maybe you only have a few kilometers of freedom before needing a bathroom emergency. You are not alone. Studies show that 30–50% of endurance athletes regularly experience gut issues during training or racing.
Symptoms can range from bloating, nausea, and cramps to, in the worst cases, vomiting or urgent diarrhea. The stress of anticipating these symptoms can make matters worse — making each run less enjoyable and more stressful.
The good news? With the right strategies, most runner’s gut symptoms are preventable, and you can regain the confidence to run anywhere without worrying about your stomach.
Why Runner’s Gut Happens
Runner’s gut is multifactorial and highly individual, but the main contributors are:
- Mechanical stress – The bouncing motion of running increases intra-abdominal pressure and can jostle the digestive organs.
- Reduced blood flow – During exercise, blood is redirected to working muscles, your heart, lungs, and skin for cooling, reducing blood flow to the gut by up to 80%. This can impair digestion and exacerbate symptoms.
- Dehydration and heat – Fluid loss and high temperatures increase nausea, cramps, and delayed stomach emptying.
- Dietary factors – High-fat, high-protein, high-fiber foods, or concentrated carbohydrates can slow digestion or leave residual nutrients in your gut, causing bloating and discomfort.
- Individual risk factors – Women, younger runners, and those running at high intensities may be more prone to gut issues.
7 Tips to Prevent Runner’s Gut
1. Train Your Gut
Your gut is highly adaptable. You can increase nutrient absorption capacity in as little as 30 days. Treat your gut like a muscle: start small, gradually increasing the amount and type of food or drink you consume during runs. Test different gels, fluids, and foods in training, not on race day.
2. Use Multiple Carbohydrate Sources
Your gut can absorb about 60g of glucose per hour, but longer sessions may require more. Using a combination of glucose and fructose can increase absorption and reduce residual carbs in the stomach — but always build tolerance gradually.
3. Reduce High-Fiber Foods Before Hard Sessions or Races
In the day or two before long or intense runs, cut back on high-fiber foods to reduce undigested material in the gut. Opt for low-fiber fruits (grapes, tomatoes, zucchini) and refined grains instead of whole-grain alternatives.
4. Go Easy on Coffee Pre-Run
Coffee can irritate a sensitive gut, especially on an empty stomach. Save your caffeine fix for post-run, or experiment with alternative sources in training.
5. Prioritize Hydration
Start your runs hydrated, and replace fluids according to your sweat rate. Track your urine color for a quick hydration check (pale straw is ideal). Sweat testing under different conditions can help determine how much to drink for longer sessions.
6. Fuel Your Daily Diet
Your daily nutrition impacts your gut’s ability to absorb carbs during exercise. A diet higher in carbohydrates increases carbohydrate absorption and oxidation during runs. Periodise your intake: include high-carb days around long sessions and moderate/low-carb days for recovery or shorter sessions.
7. Consider a Low-FODMAP Test Diet (With a Dietitian)
Some gut issues stem from foods that are hard to digest. Common culprits include onion, garlic, mushrooms, apples, pears, and dairy. A short-term, structured elimination and reintroduction plan with a qualified dietitian can help identify triggers without compromising long-term gut health.
The Takeaway
Runner’s gut doesn’t have to control your training. Most symptoms can be prevented or minimised with the right nutrition, hydration, and gut-training strategies. Imagine running 10–15 km comfortably, training without stress, and racing without constantly scanning for the nearest toilet.
If this resonates with you, it’s time to stop winging it and get a strategy that actually works. The right approach can unlock your energy, confidence, and performance — making every run more enjoyable.
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