Ultimate guide to developing your nutrition strategy for the 90 km Mont Blanc race

The ultratrail season is gradually beginning to emerge. Although physical preparation began this winter, nutrition can sometimes change. Products we are used to consuming may no longer agree with us, digestion may differ from the previous year, and we may want to change flavors and textures, etc. We will help and guide you toward products that might suit you during an ultratrail, using the Mont-Blanc 90km as an example.

In the heart of the majestic French Alps, Mont Blanc stands as a benchmark for endurance sports. The Mont-Blanc 90km crosses steep trails, snow-covered passes, and breathtaking landscapes, testing not only runners’ physical strength but also their mental resilience. The Vertical KM, 10km, Starry Duo, 23km, Mont-Blanc Marathon (42km), and even the 90km for the most ambitious runners—this event brings together more than 10,000 runners in the Chamonix Valley at the end of June.

The Mont Blanc 90km is much more than just a race. It is an adventure that requires meticulous preparation on every level, including nutrition. Indeed, managing your diet plays a crucial role in performance and recovery during this event. In this article, we will explore the fundamental principles of a nutrition plan suited to the Mont Blanc 90km, to help you achieve your goals and push your limits in this challenge.

Here, we will not discuss the days before the race. In general, dietary advice is individual. However, we can recommend slightly increasing your intake of good-quality complex carbohydrates, without overeating, and avoiding fiber if you are sensitive to it. The body is already under considerable strain during an ultramarathon, so you should not place additional stress on it with last-minute changes. Hydration is essential, both on a daily basis and before a race, so make sure to drink at least 1.5L of water per day, as well as staying hydrated during your training sessions.

1) A reminder of a few basic principles: 

During the 90-kilometer effort through the Mont Blanc mountains, nutrition plays a crucial role in maintaining energy levels, preventing fatigue, and maximizing performance. Here are some key strategies for effective race nutrition:

1.1 Constant hydration:

Hydration is essential for maintaining performance and preventing dehydration, especially in mountainous conditions where sweating and water loss may be increased. You should make an effort to drink regularly throughout the race, adjusting your intake according to the weather conditions and your own thirst. Aid stations will be available along the course so that you can replenish your water and sports drinks. Ideally, you should carry one flask of sports drink and one flask containing water or electrolytes, depending on the temperature. Maintaining adequate hydration during exercise helps compensate for losses caused by sweating and promotes the absorption of consumed carbohydrates. Alternate between water and a sports drink in small, regular sips, consuming 500 to 600 ml per hour depending on the weather conditions and your personal needs.

1.2 Carbohydrate intake:

Carbohydrates are the main source of energy for the muscles during endurance exercise. You must make sure to consume them throughout the race to maintain your glycogen stores and avoid exhaustion. Practical options such as energy gels, energy bars, and dried fruit can be easily carried and consumed during the race. Drinks also provide carbohydrates that should be taken into account in your nutrition plan.

To optimize your athletic performance, it is recommended that you maintain a carbohydrate intake of between 30 and 90 grams per hour, combining sports drinks and appropriate food according to your individual needs, tolerance, and the intensity of the physical activity. A regular nutrition strategy, with an intake every 20 to 30 minutes, helps stabilize your blood sugar. Toward the end of the effort, you can prioritize higher-glycemic-index carbohydrates to maintain your concentration and minimize fatigue, while reducing the digestive burden on your body. Vary your energy sources by including savory foods and homemade preparations, which offer an interesting alternative to industrial products. However, be careful not to exceed the recommended range of 30 to 90 g of carbohydrates per hour, to avoid gastric complications or an excess of carbohydrates that your body cannot absorb.

1.3 Balancing macronutrients:

In addition to carbohydrates, you will also need protein and fat to maintain endurance and prevent muscle fatigue. Protein-rich foods, such as protein bars or protein powder in a shaker at an aid station, can be consumed in small amounts to help support muscle recovery. Fats, such as nuts, seeds, and avocados, provide a lasting source of energy and can be included in snacks during the race.

1.4 Managing gastrointestinal issues:

Gastrointestinal issues are common during endurance races and can compromise runners’ performance. To minimize this risk, it is important to choose foods and drinks that are well tolerated by the stomach, divide portions to avoid digestive overload, and avoid foods that are too high in fiber or fat, which could cause digestive problems. By following these simple race nutrition tips, you can maintain optimal energy levels, prevent dehydration, and maximize your performance throughout this demanding mountain event.

2) Test during training:

It is crucial to train the gut to receive food intake during exertion, allowing you to test your digestive tolerance and determine the amount of energy needed to optimize performance. During training, it is essential to get the gut accustomed to ingesting and digesting energy foods while testing different products to identify those that work best for you. It is recommended to stick to food choices that have already proven effective, to avoid surprises on race day.

It is advisable to consume small amounts of carbohydrates and fluids regularly throughout the race (approximately every 20–30 minutes), making this practice a habit. Ideally, aim for at least 60 grams of carbohydrates per hour, although some may need less depending on their digestive tolerance, while others have much higher needs of up to 90 or even 100 g per hour. However, maintaining control over carbohydrate intake can considerably improve performance.

For ultra-distance events such as the 90 km Mont Blanc race, it is recommended to plan a variety of flavors and foods to avoid flavor fatigue and maintain interest in food throughout the race.

3) Study the course:

The 90 km Mont-Blanc race is an iconic event in the Chamonix-Mont-Blanc valley, renowned for its difficulty. With a distance of 92 km and 6,330 m of elevation gain, it is considered one of the most technical races in France. Although the course consists exclusively