Digestive Comfort During Races Starts Before

The gel that felt fine at kilometre 12 can feel completely different at kilometre 32. That is the reality of digestive comfort during races: it is not decided by one product or one lucky training run. It is the result of a system your gut has practised under the same carbohydrate load, fluid intake, intensity and heat stress you will face on race day.

GI issues are not a minor inconvenience when you are chasing a result. Cramping, nausea, reflux, bloating and an urgent toilet stop disrupt pace, reduce carbohydrate intake and make it harder to think clearly. The answer is rarely to stop fuelling altogether. More often, the solution is to make fuelling more predictable.

"Race-day gut problems are almost never random. They're the result of a plan that hasn't been tested at the right intensity, in the right conditions, with the right timing. The gut is trainable — but only if you practise under load. An easy Sunday run with a gel at kilometre 10 doesn't prepare you for kilometre 35 of a marathon. Build the habit in training, and the race becomes execution."
— Alistair Brownlee, Two-time Olympic Triathlon Champion and founder of truefuels

Why your gut changes when the race starts

During hard exercise, blood flow is directed towards working muscles and the skin, particularly in warm conditions. Digestion becomes less of a priority. Add impact from running, nervous-system stress, dehydration, an aggressive early pace or a concentrated drink, and the gut has a much harder job to do.

This is why an athlete can eat a substantial breakfast at home, then struggle to take down a gel in a crowded start pen. It is also why cyclists may tolerate higher intake on the bike than runners can on the run. Posture, impact, intensity and the opportunity to drink all change the equation.

The practical lesson is simple: race nutrition must be designed for the conditions in which it will be used. Do not judge a plan only by how it feels on an easy Sunday session. Test it during long runs, race-pace blocks, brick sessions and hot-weather training.

Build digestive comfort during races with consistency

Your gut is trainable. Regularly consuming carbohydrate during endurance work helps the body absorb and use it more effectively. But gut training is not an excuse to force excessive intake overnight. Increase the challenge gradually, then repeat it until it is routine.

For many endurance athletes, a starting point of 30–60g of carbohydrate per hour is manageable. Longer events and athletes with well-practised protocols may work towards 60–90g per hour, and sometimes more where multiple transportable carbohydrates are used. The right target depends on race duration, body size, intensity, event format and what you can absorb without symptoms.

The most useful number is not the highest number you have seen online. It is the amount you can take consistently while holding your intended pace.

Keep the carbohydrate source familiar

Race day is not the place to test a new flavour, a different gel texture or a heavily caffeinated product. Familiarity reduces both physiological and mental friction. You should know how each serving tastes after two hours, how much water it needs and whether it still appeals when you are hot and working hard.

Flavour fatigue matters. A sweet product that is appealing for the first hour may become difficult to tolerate later. Some athletes do better with a neutral or lighter flavour profile; others prefer to alternate flavours. Test this in training rather than improvising at an aid station.

Match each feed with your fluid plan

Concentrated carbohydrate without enough fluid can sit heavily in the stomach. Equally, drinking excessive plain water can leave you sloshing and may dilute blood sodium. The aim is not to chase a universal litres-per-hour target. It is to use a fluid plan that reflects your sweat rate, the weather, access to drinks and the sodium content of what you are taking.

Start by observing body mass changes and thirst across representative training sessions. A large loss in body mass, increasing thirst, headache or a falling ability to tolerate gels can indicate that your hydration plan needs attention. A visibly overfull stomach, frequent urination and persistent sloshing can indicate the opposite.

In warmer conditions, sweat losses rise and electrolyte replacement becomes more consequential. Sodium helps maintain fluid balance and supports the drive to drink, but more is not automatically better. Match your strategy to your own sweat losses, the race environment and the duration of the event.

The pace-fuelling connection athletes miss

A gut plan cannot compensate for a poor pacing plan. Going above sustainable effort early in a race increases stress and makes nausea more likely, even if your nutrition is otherwise sound. The common pattern is familiar: an athlete starts too hard, misses the first planned feed because breathing is elevated, then tries to catch up with multiple gels later. That is a reliable route to discomfort.

Fuel early, before the deficit is obvious. For most races lasting beyond about 90 minutes, begin taking carbohydrate within the first 20–30 minutes, then use small, regular feeds. Smaller doses every 15–20 minutes are often easier to absorb than large, infrequent hits. The exact timing can vary, but the principle should not: avoid long gaps followed by panic fuelling.

Practise taking fuel at race effort. If you cannot swallow comfortably at your target threshold pace, slow briefly at an aid station, take fluid, and return to rhythm. Losing a few seconds is preferable to losing the next 10 kilometres to stomach distress.

truefuels Performance Gel

40g of carbohydrate at a 1:1 glucose-to-fructose ratio, with electrolytes built in. Fluid texture, no artificial flavours, sweeteners or preservatives — built to repeat 2–3 times an hour without the gut cost that comes from lower-quality formulas.

See the gel →

Start race day with less digestive risk

The final 24 hours are not the time for dietary heroics. A high-fibre meal, unfamiliar restaurant food, excess alcohol or a large fat-heavy dinner can create problems before the gun goes. For some athletes, reducing fibre for the day before a key race lowers stool bulk and the risk of urgent bowel movements. It depends on the individual, so trial it before an important event.

Your pre-race meal should be familiar, carbohydrate-led and eaten with enough time to digest. Many athletes perform well with a meal 2–4 hours before the start, followed by a small carbohydrate top-up closer to the gun if needed. The best timing depends on start time, appetite and travel logistics.

Caffeine deserves the same respect as any other performance tool. It can improve alertness and perceived effort, but it can also increase bowel urgency, reflux or jitters. If caffeine is part of your strategy, use the dose and timing you have already tested. Do not combine coffee, caffeinated gels and an energy drink simply because race morning feels important.

A practical protocol for training your gut

Use one long or race-specific session each week to rehearse the full system. Begin with the breakfast you intend to use, take in carbohydrate at your planned hourly rate and drink according to the conditions. Record what you took, when you took it, your perceived gut comfort and any symptoms.

If the session goes well, repeat it. If it does not, change one variable at a time. Reduce the serving size, take feeds more frequently, add water with gels, lower the caffeine dose or adjust sodium for the temperature. Changing everything at once teaches you very little.

A simple log is enough. Note the session duration, temperature, pace or power, carbohydrate per hour, fluid intake, sodium intake and symptoms. Patterns emerge quickly. You may find that 70g per hour works on the bike but 55g works better on the run, or that a particular flavour becomes difficult after three hours.

When symptoms need a different response

Not every GI problem is a fuelling problem. Recurrent pain, blood in the stool, unexplained weight loss, persistent vomiting or symptoms that also occur outside training warrant medical assessment. Athletes with diagnosed gastrointestinal conditions should work with a qualified clinician or sports dietitian rather than trying to solve the issue through increasingly restrictive race-day habits.

For occasional race-related discomfort, do not assume your gut is weak. Treat it as feedback from the system. Was the pace too high? Was the drink too concentrated? Did you miss early feeds? Was the day hotter than your testing conditions? Precision beats guesswork.

The strongest race nutrition plan is the one that still works when you are tired, warm and under pressure. Train the intake, control the variables you can, and arrive on the start line knowing exactly what your gut has been prepared to do.

40g of carbohydrate. Precisely dosed. Gut-friendly.

40g CHO per gel, 1:1 glucose-to-fructose ratio, electrolytes built in. Two salt variants, no artificial sweeteners or preservatives. The gel that works when the race gets hard.

See the Performance Gel →

★ 4.86 — 200+ reviews Built by Alistair Brownlee, Two-time Olympic Triathlon Champion