The Long Run Gut Guide
Trail Tips | Nutrition & Fuelling
Practical long-run fuelling for sensitive stomachs
How to Fuel
Long Runs Without Gut Issues
When your run stretches past 90 minutes, fuelling shifts from optional to essential. But this is also where gut discomfort can enter the picture.
Bloating. Cramps. Nausea. Sloshing. Urgent toilet stops. Or the feeling that nothing will go down once you are already deep into the run.
This guide is for the runner who wants to go long, stay steady and build a fuelling plan her body can trust.
Gut comfort is not luck. It is something you practise.
The aim is not to force food in. The aim is to train your body to recognise fuel, fluid and timing before race day asks for it.
Trail Tip · 01
Why gut issues happen
Gut discomfort during long runs is common, but it is not inevitable. During long or harder efforts, blood flow is prioritised toward working muscles and temperature regulation. Digestion can slow. Add running impact, heat, dehydration, nerves, unfamiliar products or taking in too much at once, and the gut can become overloaded.
For some women, gut comfort may also shift across the menstrual cycle, during perimenopause, or in high-stress life seasons. Some notice more bloating, constipation, nausea, appetite changes, fluid shifts or sensitivity to certain foods. Others notice little change. The key is to track your own pattern rather than assume one rule applies to everyone.
Trail Tip · 02
Train your gut like you train your legs
Gut issues are not a sign of weakness. They are often a sign that the fuelling system has not been practised enough.
Your digestive system can adapt to fuelling during movement, but it needs repetition. Start small, build gradually and use training to learn what your body accepts.
How to start
Try half a gel, a few chews, a small amount of sports drink, or a small piece of real food during shorter runs.
Build toward a carbohydrate amount that suits your distance, intensity and tolerance. Many runners start around 30 to 60 grams per hour for longer sessions.
Start fuelling around 30 to 45 minutes in, then continue regularly.
Practise with the effort, weather, terrain, gear and products you are likely to use on race day.
Trail Tip · 03
Start with a calm baseline
What you eat before the run matters too. In the 24 hours before a long run, notice whether certain foods tend to trigger symptoms for you.
For some runners, this may mean reducing very high-fibre foods, cruciferous vegetables, large amounts of dairy, artificial sweeteners, fried foods or unfamiliar meals close to the session. This is individual. Do not remove foods unnecessarily. Use training to learn what your body prefers before long efforts.
Trail Tip · 04
Eat early, not late
Give yourself enough time after a full meal before running. For many runners, 90 to 120 minutes works well, but your own tolerance matters.
Simple pre-run options
Toast with nut butter and banana.
Oats with banana and cinnamon.
Rice with egg or tofu.
A smoothie with carbohydrate and protein.
A simple bagel, wrap or sandwich.
Trail Tip · 05
Fuel before you feel flat
Once you are running, small amounts often work better than big hits. Start around 30 to 45 minutes in, then top up every 25 to 35 minutes. This reduces the load on the gut and helps prevent the energy drop that makes everything feel harder later.
If you often feel sick after gels, the issue may not be the gel alone. It may be timing, concentration, dehydration, heat, pace, or taking it without enough fluid.
Trail Tip · 06
What to eat on long runs
Whole-food options
Boiled potato with salt, dates, rice cakes, banana oat cookies, small sandwiches, salted wraps or simple savoury bites.
Commercial options
Energy chews, hydration mix, sports drink, gels, maple syrup packs, waffles or bars.
Aid Station can be a useful place to trial different options before race day, especially if you want to compare gels, chews, hydration mixes and real-food-style products. The important part is not the brand. It is finding what works for your system in training.
Trail Tip · 07
For plant-based or gut-sensitive runners
Use familiar staples first: rice, potato, oats, banana, maple syrup, peanut butter, tofu, simple wraps or low-fibre breads.
Be cautious with sugar alcohols such as sorbitol, xylitol and other sugar-free sweeteners, as these can trigger gut symptoms for some runners. If you have IBS, persistent gut symptoms or a known food intolerance, consider working with a sports dietitian.
Trail Tip · 08
Hydration matters too
Dehydration can make gut issues worse, but simply drinking more plain water is not always the answer. Sip regularly and include electrolytes or sodium when duration, heat, sweat rate and conditions call for it.
Fuel and fluid work together. Your stomach may struggle if you take in concentrated carbohydrate without enough fluid, or if you drink large amounts of plain water without enough sodium across a long effort.
Listen to your body, not the marketing.
You do not need the most popular product to run well. You need a plan your body recognises.
Reflection prompt
What does strong fuelling feel like in my body?
Where might I be fuelling from fear, pressure or comparison, instead of practising a plan that genuinely works for me?
Practise the fuel before the run demands it
Written by the Her Trails coaching team
Trail Tips are practical coaching notes for women who train, race and run on trails.
General education only, not medical or nutrition advice. If you experience persistent gut symptoms, vomiting, blood in stool, fainting, severe dehydration, or ongoing difficulty fuelling, seek support from a qualified health professional or sports dietitian.
