Ultramarathon Nutrition: A Simple, Correct Strategy

Hey! I’m Irene — PhD in Biomedicine, sports scientist, and certified running & ultrarunning coach.

My coaching is grounded in evidence-based science, not social media trends.. If you need help with your training and/or race nutrition, you can book a call with me here:👉 https://calendly.com/train4bodymind/

Disclaimer: This guide is for educational purposes only and is not intended as medical or individualised prescription. If you have a medical condition, gastrointestinal disorder, or are under clinical care, please consult a registered healthcare professional.

Note: Always practise your nutrition in training — nothing new on race day. If you have a history of severe gastrointestinal issues, allergies, or food intolerances, seek personalised guidance before applying these strategies

BEFORE the run / race

Goal:

Start fuelled with sufficient glycogen stores, as carbohydrates are the main energy source for working muscles during endurance exercise. You also want to be well hydrated — ideally hydration should start the day before — and begin with a calm, settled gut.

• 2–3 hours before

Eat a carbohydrate-rich, low-fibre, low-fat meal that is easy to digest and supports glycogen availability without overloading the gut.

Examples include white rice, white bread with jam or honey, oats, pancakes, or potatoes. Protein should be moderate, and fat kept low.

• 30–45 minutes before (optional)

This is especially useful for longer or more intense races.

A small carbohydrate top-up can help stabilise blood glucose and delay early fatigue. Examples include a banana, drink mix, a sports drink, or a small gel.

• Avoid

Fats and proteins slow gastric emptying, which can delay carbohydrate absorption and increase the risk of GI distress once exercise starts.

Examples:

• High-protein shakes

• Nuts, seeds, and high-fat foods

• Any foods or products you have not tested in training

⚠️ Common mistakes (BEFORE)

• Prioritising protein over carbohydrates

• Choosing foods that are “healthy” but high in fat or fibre

• Skipping food due to fear of GI symptoms

• Starting underfuelled in an attempt to “protect the gut”

DURING the run / race

Goal: Maintain energy availability, stabilise blood glucose, and minimise gastrointestinal distress so pace and decision-making are not compromised.

• Carbohydrates

For races over 4h, aim for ~60–90 g of carbohydrates per hour, depending on individual tolerance, intensity, and race duration. Some studies support intakes up to 120 g/h, but this requires high tolerance and deliberate gut training.

Using a mix of carbohydrate sources improves absorption and flexibility. This may include:

• Drink mixes

• Gels

• White-bread sandwiches

• Mashed potatoes or rice balls

As fatigue increases, liquid carbohydrates are often easier to tolerate than solids.

• Gut training

Fuel tolerance is trainable, just like fitness.

Practise fuelling during training sessions and gradually increase carbohydrate intake over time. As a general guide:

• Beginners may start around 20–25 g/h

• More experienced athletes may start closer to 40 g/h

Many athletes who describe themselves as having a “sensitive gut” improve significantly with consistent exposure and appropriate dosing.

• Electrolytes

Use drink mixes and/or salt capsules, and adjust intake based on:

• Heat

• Sweat rate

• Race duration

• Sodium/Potassium content of foods, gels, and drink mixes

Focus on adequate sodium intake, as sodium is the primary electrolyte lost in sweat.

Potassium intake is usually sufficient from foods and sports products, and during ultramarathons sodium intake is typically the priority

That’s why drinks like coconut water are not ideal as they are relatively high in potassium but low in sodium - the opposite of what most ultra/runners need.

• If GI issues appear

GI discomfort does not mean fuelling should stop.

Briefly slowing down, switching to liquid carbohydrates, and reducing concentration (not total intake) can help settle symptoms. The priority is to keep carbohydrates coming in.

If vomiting occurs, pause solid intake temporarily, focus on small sips of fluids with electrolytes, and reintroduce carbohydrates gradually once symptoms settle.

⚠️ Common mistakes (DURING)

• Fuelling only when hunger appears

• Relying mainly on protein bars or flapjacks

• Avoiding gels without having trained effective alternatives

• Using coconut water as the main electrolyte source

• Completely stopping carbohydrate intake when GI discomfort starts

• 
  

AFTER the run / race

Goal: Initiate recovery immediately to reduce cumulative fatigue, support glycogen resynthesis, and prepare the body for the next training stimulus.

• As soon as possible (within ~30 minutes)

Combine carbohydrates and protein to support recovery — you need both.

A ratio of approximately 1 part protein to 3 parts carbohydrates has been shown to support glycogen resynthesis and initiate muscle repair, particularly when glycogen stores are low.

Protein supports muscle repair, while carbohydrates remain the priority for restoring energy availability.

Simple, effective options include:

• Chocolate milk

• Banana and yoghurt smoothie

• A recovery shake that contains carbohydrates

  
  

• If the main meal is delayed

Do not wait. Take a snack first to start recovery processes.

• Later

Eat a balanced meal containing carbohydrates, protein, and micronutrients, and rehydrate progressively over the following hours.

⚠️ Common mistakes (AFTER)

• Waiting until the next meal instead of refuelling straight away

• Focusing only on protein and neglecting carbohydrates

• Underestimating recovery needs after long sessions

• Repeating long runs without adequate refuelling between them

  
  

Key take-home messages

A “careful” strategy is not always an effective one. Most gut issues are fuelling and training issues. The gut adapts — if you train it. Strong finishes come from consistent, adequate fuelling.

Need help applying this to your training or race?

I work 1:1 with committed and serious ultrarunners to build individualised fuelling and training strategies that actually work on race day.

📅 Book a call here:👉 https://calendly.com/train4bodymind/