Ultrarunning and Nutrition
The Basics of Ultrarunner Nutrition
Written by Sports Nutrition Expert and Registered Dietitian
Ultrarunning is a wonderful, challenging and rewarding experience, but it also places unique demands on the body and especially on nutrition. Those preparing for their first or second ultra run will quickly notice that good basic fitness alone is not enough: energy and fluid intake are more crucial than any single workout.
In this blog post, I will discuss the basic principles of ultrarunning nutrition.
1. Energy need during ultrarun?
According to international sports nutrition recommendations, 60–90 g of carbohydrates per hour improves performance in long-term performance1,2. Combining different carbohydrate sources (glucose + fructose) can improve absorption and allow for a higher total intake without stomach upset. The absorption capacity of glucose alone is 60 g/h1.
The ultrarun lasts for several hours, sometimes even a day or more. This requires high energy consumption, and the availability of carbohydrates is emphasized because they are the fuel that allows the body to maintain performance.
2. What should you do before the ultrarun?
A) Refueling carbohydrates 1–3 days before the race
For novice runners, it is often enough to emphasize carbohydrates and not necessarily extreme “loading”. The goal is to replenish muscle glycogen stores as efficiently as possible.
Recommendation: In practice, this can be done by eating carbohydrate-containing food at every meal during the 1-2 days before the race. Quantitatively, this can be thought of as about 1/2 of the plate is carbs, e.g., rice or pasta. In addition, the evening snack and breakfast should contain carbohydrates, such as oatmeal, honey or banana.
Easy refueling foods include:
- Rice and pasta
- bread and porridge (breads preferably with less than 6 g/100 g of fiber)
- bananas, smoothies, dry fruits (caution here, these may contain a lot of fiber)3
B) Hydration the day before the race
The most important goal of the day before is to ensure sufficient fluid intake.
Drink throughout the day, not in large quantities at once. The goal for the day is about 2–2.5 l. Monitoring the color of urine is an easy home remedy: light yellow or light is good.
C) Reducing fiber and fatty foods the day before the race
Reducing your fiber intake is important to reduce the risk of stomach upset while running. Fiber increases the amount of intestinal contents, which can be uncomfortable or cause stomach upset during long performances.
Fat, however, slows gastrointestinal absorption and adds to total energy intake without supporting glycogen restoration. It may also affect appetite control, subsequently impacting carbohydrate intake and perceived well-being.
3. Energy intake during ultra running
Carbohydrates – what and how much?
A suitable goal for most runners is:
- 30–60 g of carbohydrates per hour
The goal of more advanced and professional runners is:
- 60–90 g per hour (requires practice)
Good sources are for example:
- Energy Gels
- Sports drinks
- Energy bars (low fat)
- rice, banana, pasta, salted biscuits, low-fiber bread
- small quantities of dried fruit, loose candy
Important: Train your gut. Getting your gut used to carbohydrates in training reduces the risks in the race itself. If you use sports products offered in competitions, it is important to practice using these products beforehand.4
4. Hydration and electrolytes during ultrarun
A) The basic principle of drinking
The goal is to avoid both underhydration and overhydration, as each can negatively affect performance.
Recommended intake: In general 400–800 ml per hour is appropriate. This range should be adjusted based on environmental conditions, individual sweat rate, and exercise intensity. Drinking to thirst may be appropriate approach5, but having a planned drinking schedule as a backup may help to decrease the risk of under-/overhydration.
A sports drink that contains carbohydrates + electrolytes is often the best option for long-term performance.
B) Salt
Salt helps replace sodium lost through sweating and plays an important role in maintaining fluid balance6. It also supports efficient carbohydrate absorption. Most commercially available sports drinks already contain sodium.
Important Consideration:
Excessive salt intake is common, often due to the assumption that more is “safer”. This practice carries potential risks, including:
- Gastrointestinal discomfort
- Excessive fluid retention and an increased risk of electrolyte imbalance, including hyponatremia (which may appear counterintuitive, right?)5,6
Salt itself does not enhance performance. Its primary function is to support fluid balance and improve energy absorption.
There is also evidence indicating that salt (sodium) intake during exercise lasting up to 30 hours does not prevent exercise‑associated hyponatremia (EAH)5,7. Instead, excessive sodium intake may increase the risk of EAH by stimulating thirst and thereby promoting overhydration7.
To sum up, salt intake helps regulate fluid balance and improve energy absorption. Excessive salt intake may increase risk for GI issues and EAH risk.
Recommended intake:
An appropriate salt intake is typically 0.8–1.5 g per hour, corresponding to approximately 300–600 mg of sodium per hour8. Total intake should always account for the sodium already present in sports drinks, gels, and other nutritional products.
For most recreational ultrarunners, appropriate sodium intake may fall in the range of ~200–400 mg per hour, depending on intensity, conditions, and individual sweat rate.
5. What to take with you to the run?
Very important thing is to plan your own energy and fluid intake before the race – and stick to it! By drinking just to quench your thirst or by consuming energy when you feel tired, you will almost certainly have problems.
- Sports drinks and/or gels that you know your stomach can handle
- Enough water and empty soft bottles as a backup
- A small amount of salt (also tablet or electrolyte drink works)
- Backup gels, because you might need that extra energy
- Tested options – don’t try anything new in the competition
6. The most common nutrition mistakes during ultrarun
- Insufficient energy intake
- Gels or drinking started too late
- Insufficient glycogen stores at the start of the race
- A new gel or beverage that hasn’t been tested
- Inadequate fluid intake
These can easily be avoided with good preparation in advance and proper refueling.
Hopefully, these tips will help you prepare for your next longer running event.
References
1. Jeukendrup, A. A Step Towards Personalized Sports Nutrition: Carbohydrate Intake During Exercise. Sports Med. Auckl. Nz 44, 25–33 (2014).
2. Burke, L. M., Hawley, J. A., Wong, S. H. S. & Jeukendrup, A. E. Carbohydrates for training and competition. J. Sports Sci. 29 Suppl 1, S17-27 (2011).
3. Valenta, R., Valenta, R., Dorofeeva, Y. & Dorofeeva, Y. Sport nutrition: the role of macronutrients and minerals in endurance exercises. Foods Raw Mater. 6, 403–412 (2018).
4. Jeukendrup, A. E. Training the Gut for Athletes. Sports Med. Auckl. Nz 47, 101–110 (2017).
5. Hoffman, M. D. & Stuempfle, K. J. Sodium Supplementation and Exercise-Associated Hyponatremia during Prolonged Exercise. Med. Sci. Sports Exerc. 47, 1781–1787 (2015).
6. Klingert, M. et al. Exercise-Associated Hyponatremia in Marathon Runners. J. Clin. Med. 11, 6775 (2022).
7. Kerksick, C. M. et al. ISSN exercise & sports nutrition review update: research & recommendations. J. Int. Soc. Sports Nutr. 15, 38 (2018).
8. Hoffman, M. D. & Myers, T. M. Case Study: Symptomatic Exercise-Associated Hyponatremia in an Endurance Runner Despite Sodium Supplementation. Int. J. Sport Nutr. Exerc. Metab. 25, 603–606 (2015).
Article updated April 24, 2026 – Petri Luhio
