Ultramarathon Nutrition Guide for Race Day
October 3, 2026 Share LinkThe first missed feed rarely feels dramatic. You run past an aid station, take a few mouthfuls because you are still feeling strong, then discover an hour later that the climb has become a negotiation. A sound ultramarathon nutrition guide is not about finding one miracle gel. It is about creating a simple, practised system that keeps energy, fluids and decision-making moving when the miles get long.
Ultra nutrition is personal, but it should never be improvised on race day. Temperature, altitude, pace, duration, available aid-station food and your own gut all change the plan. The goal is not to eat perfectly. It is to take in enough, early enough, in a form you can tolerate while moving over rough ground.
Ultramarathon nutrition guide: start with carbohydrates
Carbohydrate is the main fuel to prioritise during an ultra. Your body can store only a limited amount as glycogen, and hard climbing, faster running and cold conditions can drain those stores quickly. Once they are low, the familiar signs appear: a sudden drop in power, foggy thinking, irritability, shaky legs and a growing urge to walk every rise.
For most runners, a useful starting point is 60 to 90 grams of carbohydrate per hour. Newer high-carbohydrate approaches can reach 90 grams or more, but only when the gut has been trained to handle it. Starting at 90 grams an hour because it looks good on a race-plan spreadsheet is a reliable way to turn a big day into a stomach-management exercise.
If you are new to fuelling, begin nearer 40 to 60 grams per hour on long training runs. Build gradually across several weeks by adding a small amount at a time. Keep notes on what you ate, when you ate it, how much fluid you drank and how your stomach felt. This is more useful than guessing after a rough run.
Gels are convenient, light and easy to track, but they are not the only answer. Chews, drink mix, soft bars, bananas, boiled potatoes, rice balls, flapjack, soup and small sandwiches can all earn a place in an ultra plan. Sweet foods often work well early, while savoury choices can become more appealing after several hours. Carry options with different textures and flavours so you can adapt without abandoning your carbohydrate target.
Eat before you feel empty
Set a timer or use a regular cue, such as every 20 minutes, and take a small feed. A gel every 30 minutes may suit one runner; another may prefer alternating drink mix and solid food. Frequent small doses are generally easier on the gut than waiting until you are hungry and then forcing down a large serving.
The same rule applies on descents. Fast downhill running can make eating awkward, but it is also a chance to fuel before the next climb asks more of you. Walk the steepest sections if necessary, take in food deliberately, and protect the energy you will need later.
Hydration and electrolytes without overdoing either
There is no single hydration number that fits every runner. A cool, wet mountain race demands something very different from a hot, exposed summer ultra. Start with your thirst, then adjust for conditions, sweat rate and the practical capacity of your running vest.
Many runners will drink somewhere around 400 to 800 ml per hour, but this is a broad range rather than a target to force. Drinking excessively can be as dangerous as drinking too little, particularly over long events. Pale urine alone is not a useful race-day metric, and a bloated stomach or frequent sloshing is often a sign to reassess rather than keep drinking.
Electrolytes, especially sodium, matter when you are sweating for hours. They can help replace losses and make fluids more appealing, but they do not cancel out poor pacing or solve every cramp. Sodium needs vary widely. If you finish training runs with salt crusted on your clothing, race in heat or know you sweat heavily, you may need more than a runner in cool conditions. Sports drink, electrolyte tablets, capsules and salty aid-station food can all contribute.
Avoid treating salt as an emergency cure-all. Cramp can come from fatigue, climbing load, heat, low carbohydrate intake and unfamiliar effort as much as electrolyte loss. Consistent fuelling, sensible pacing and enough fluid are usually the stronger foundations.
Match your carrying system to the course
Look at the longest stretch between reliable water points, then add a margin for heat, queues or a missed refill. A vest with two soft flasks is ideal for many races, while a bladder can make sense on remote routes where stopping to refill is inconvenient. Some runners prefer one flask with water and one with carbohydrate drink, which makes it easier to separate fuel from hydration.
Practise opening packets, refilling flasks and eating while wearing the exact kit you plan to race in. Small frustrations become much larger when your hands are cold, you are wearing gloves or you are trying to keep moving on a narrow trail.
Build a race plan around the route
Your nutrition plan should follow the course profile, not just the clock. A long climb may raise effort and sweat rate, while a runnable valley may be the easiest place to eat solid food. Aid stations should support your plan, not replace it. Know what will be available, but carry foods you trust in case the selection is limited or your appetite changes.
Before the race, write down three things: your hourly carbohydrate target, your likely fluid range and the food you will carry between each aid station. Keep the plan simple enough to follow when tired. For example, you might aim for 60 grams of carbohydrate per hour through a combination of drink mix and a gel, refill both flasks at every second aid station, and collect a savoury snack at the halfway point.
Caffeine can be useful late in a race, particularly if you already use it well. It may sharpen focus and make effort feel more manageable, but it can also worsen nausea, anxiety and urgent toilet stops. Treat it as a tested tool, not a rescue button. Save a caffeinated gel or drink for the hours when you know fatigue usually arrives.
Train your gut as deliberately as your legs
Long runs are rehearsals for nutrition, not just fitness. Use them to test the food, drink, flask arrangement and timing you expect to use in your event. Test in similar weather where possible, and include climbing if the race has it. A fuel plan that works on an easy three-hour run may feel very different after seven hours of climbing and descending.
Race week is not the time for drastic experiments. Eat familiar meals, prioritise carbohydrates in the days before a long event and keep fibre, spice and rich foods in line with what you know your stomach tolerates. The pre-race meal does not need to be complicated: choose a familiar carbohydrate-based meal with some protein, leave enough time to digest it, and arrive at the start calmly fuelled rather than overfull.
If nausea starts during the race, slow the intake rather than stopping it entirely. Sip fluid, switch flavour or texture, and try a small salty or bland option. Cooling down, easing the pace on a climb and taking a few minutes to settle the stomach can prevent a minor wobble becoming a long decline. Persistent vomiting, confusion, severe headache or worsening symptoms deserve medical support at the next available point.
The best plan is the one you can repeat when the weather turns, your legs hurt and the finish still feels far away. Build it on ordinary long runs, carry it in kit you trust, and give yourself permission to adjust without abandoning the basics. A steady bite, a measured drink and the next trail marker can be enough to bring the day back under control.
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