Introduction
Ultras aren't won by trained legs alone: they're also won in the stomach and the hydration pack. For hours on end, the body burns hundreds of calories, loses liters of sweat, and must keep functioning. Without regular intake of energy and water, reserves deplete, blood sugar drops, and performance collapses. Conversely, poor nutrition can lead to nausea, digestive issues, or even chills. This comprehensive guide explains why nutrition and hydration are trail running cornerstones, how much to consume, and how to organize your refueling strategy to cross the ultra finish line feeling strong.
1. Why Nutrition and Hydration Are Essential
In a long-distance trail run, eating and drinking serve several purposes:
Maintain energy: endurance effort consumes huge amounts of calories. Without intake, the body draws from glycogen then fat reserves and quickly tires.
Ensure hydration and electrolyte balance: heavy sweating leads to water and salt loss. Regular intake of fluids and minerals prevents dehydration and cramps.
Prevent injuries and aid recovery: good nutrition reduces muscle breakdown and helps repair fibers during the effort. Protein consumed during the race provides essential amino acids to maintain lean mass.
Maintain stable weight and mental performance: nutrition supports well-being, focus, and motivation. Regular intake prevents energy slumps and supports morale.
2. Determining Your Energy Needs
The body burns between 400 and 800 kcal per hour during an ultra. To avoid "hitting the wall", it’s recommended to consume 200 to 400 kcal per hour from carbs, fats, and proteins. Rations vary based on body size, intensity, and weather, but these are useful guidelines.
2.1 Carbohydrates
20 to 50 km trails: 30 to 60 g of carbs per hour.
Ultra: 40 to 80 g/h.
Split intake every 30 to 45 min to stabilize blood sugar.
Vary textures (gels, drinks, bars, fruit purees, dried fruits) to avoid nausea.
Limit fiber and fat during the effort.
2.2 Proteins and Fats
For efforts over 8 hours: 10 to 15 g of protein per hour (protein bars, cheese, nuts).
Fats: 10 to 20 g/h in very long races to provide lasting calories – test during training.
2.3 Electrolytes
Recommended sodium: 500 to 700 mg/h.
Hydration: 500 to 1000 ml/h depending on temperature and intensity.
Isotonic drinks or electrolyte tablets make up for these losses.
3. Hydration: How Much and How?
Drink 500 to 750 ml per hour (up to 1 L/h in hot weather).
Don’t wait until you're thirsty: drink every 10–15 minutes.
Use an isotonic drink (~30 g of carbs/500 ml).
Adjust sugar concentration: more concentrated in cold weather, more diluted in heat.
Test your drink during training to ensure tolerance.
4. Choosing the Right Foods
4.1 Sweet
Gels, energy drinks, cereal bars, dried fruits.
Fruit/vegetable purees or compotes that are easy to swallow.
Jam, honey, or almond paste on white bread.
4.2 Savory
Broths, soups rich in sodium and fluids.
Chips, salty biscuits, crackers to balance the sweetness.
White bread sandwiches with cheese or ham.
Mashed potatoes or sweet potatoes.
4.3 Anti-nausea Tips
Alternate sweet/savory every 30–45 min.
Chew slowly to aid digestion.
Test all foods beforehand.
5. Refueling Strategy
5.1 Planning
Study the race profile to estimate needs.
Plan for 500 ml of drink per hour, adjust based on weather.
Distribute food in accessible pockets.
Use aid stations to refill, diversify food, and relax.
5.2 Adjust to Conditions
Heat/altitude: more hydration, electrolytes, easy-to-swallow foods.
Cold: solid/warm foods, broths, purees, thermos.
Duration: for >100 km, add fats (10–20 g/h) and proteins (10–15 g/h); for 50 km, focus on carbs.
5.3 Listen to Your Body
Adjust based on digestive tolerance and sensations: use purees or drinks if the stomach feels full, solid food if hungry.
6. Before and After the Race
6.1 Before
Meals rich in simple/complex carbs, low in fiber/fat.
Regular hydration + salty drink the day before.
Prepare and test all nutrition gear.
6.2 After
Within 30 min: recovery drink (carbs + proteins).
Drink regularly to replace water and sodium losses.
Full meal with carbs + proteins within 2 hours, then regular snacks.
Enjoy food without overdoing alcohol.
Conclusion
Success in an ultra depends on fueling and hydrating the machine: plan your aid station strategy, consume 30–80 g of carbs per hour, add 10–15 g of protein and 10–20 g of fat in very long races, drink 500–1000 ml/h with 500–700 mg of sodium. Vary your foods, test during training, and stay flexible based on conditions and how you feel. With experience, nutrition and hydration become second nature, helping you go the distance without bonking or upsetting your stomach.