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Meet Evelien Mertens, CrossFitter, triathlete, dietitian & doctor in movement and sport sciences.

Sports and plant-based food, many have been written about it and many different points of view circulate. Can you do elite sports on plant-based food? Do you get enough resources from plant-based foods to do strength training? Can you be healthy and sustainable for yourself, the planet and animals and perform well? Expert Evelien Mertens passionately answers this questions.

You are a nutrition and dietetics researcher and Flemish Plant-based dietitian, where did that passion start for you?

My interest in nutrition arose primarily during my PhD. I had the opportunity to start a PhD after my studies Master in physical education and movement sciences (graduation variant fitness and health). The topic of my PhD was largely nutrition-related. Reading more literature regarding nutrition only further piqued my interest. I then decided to study the Bachelor of nutrition and dietetics in distance learning at Erasmus University College. After graduation, I started working as a researcher in the nutrition and dietetics program at Erasmus University College and as a dietician in a secondary occupation. Since I was already eating completely plant-based, I wanted to specialize in this field as a dietician. When Chris Kerfs of Kintu founded the working group of the Vlaamse Plantaardige Diëtisten, I did not hesitate to join them. It is a great team who all want to work for a more plant-based world.

Have you consistently eaten plant-based food since the beginning of your career?

I have been eating completely plant-based for almost 8 years now. At the exact same time I started CrossFit, so everything from muscle strength and muscle mass that was built is on a plant-based diet.

What is your main motivator to eat plant-based?

Animal welfare was the main reason for me to shift to a plant-based nutritional pattern. In my teenage years, I often said I would later eat veggie or vegan, but at that time I still experienced too much pressure to drop animal products. I do remember feeling gross about it many times and eating it reluctantly. The shift to a completely plant-based nutritional pattern must have been just about one of the best decisions of my life.

A healthy plant-based diet is not only a win for health, the planet and animals, but also for athletic performance.

What are the benefits of a plant-based diet in sports?

Many recent studies show that endurance athletes have benefits when consuming plant-based foods. This is because of the presence of antioxidants in plant-based foods, the lower saturated fat content, the greater amount of carbohydrates in plant-based foods and, consequently, the higher glycogen stores. Plant-based foods decrease blood viscosity, increase arterial flexibility and vessel diameter, leading to increased blood flow so that more oxygen and nutrients can get to working muscles and waste products are removed. Plant-based nutrition also has a beneficial effect on indicators of inflammation and provides immune system benefits. It also has low acidity and alkalizing properties, reducing body acidification. Strength athletes are more skeptical of plant-based foods, but again, both components are perfectly compatible. Thus, a healthy plant-based diet is not only a win for health, the planet and animals, but also for athletic performance.

What are the focal points in the diet of an avid athlete? Are there any specific differences compared to the diet of a hobby athlete?

Depending on the type of sport, there will be a higher need for carbohydrates (in endurance athletes) and/or protein (in strength athletes). Also, for example, iron requirements may be slightly higher in (semi-)professional athletes compared to hobby athletes. If the diet is healthy and varied, and supplementation of vitamin B12, vitamin D (only in the winter months) and omega-3 is carefully applied, there will be no problems.

What advice would you give to athletes who want to eat plant-based?

It is important that they eat healthy (= minimally processed food or as unprocessed as possible) and varied foods to get all the nutrients in good proportions. Also essential is that they eat enough to nourish their body and that each main meal consists of a carbohydrate source, a protein source, a fat source and vegetables and/or fruits. Supplementation of vitamin B12, vitamin D (in the winter months only) and omega-3 is necessary. Sports-specific supplements such as creatine or beta-aline depend on the athlete's objective, type of sport, preference, etc.

Do you have any advice on interesting reads?


Matt Frazier & Robert Cheeke - The plant-based athlete

TJ Watefall - The plant-based power plan

Review articles

Pohl, A., Schünemann, F., Bersiner, K., & Gehlert, S. (2021). The Impact of Vegan and Vegetarian Diets on Physical Performance and Molecular Signaling in Skeletal Muscle. Nutrients, 13(11), 3884.

Lynch, H., Johnston, C., & Wharton, C. (2018). Plant-Based Diets: Considerations for Environmental Impact, Protein Quality, and Exercise Performance. Nutrients, 10(12), 1841.

Shaw, K. A., Zello, G. A., Rodgers, C. D., Warkentin, T. D., Baerwald, A. R., & Chilibeck, P. D. (2022). Benefits of a plant-based diet and considerations for the athlete. European journal of applied physiology, 122(5), 1163–1178.

Barnard, N. D., Goldman, D. M., Loomis, J. F., Kahleova, H., Levin, S. M., Neabore, S., & Batts, T. C. (2019). Plant-Based Diets for Cardiovascular Safety and Performance in Endurance Sports. Nutrients, 11(1), 130.

What is your favourite meal?

I generally like to eat very much. :-) So naming a favorite dish is not so easy. I do love a vegetable lasagna with lentils, for example.

How is dietetics and plant-based eating connected for you?

I believe it is our duty as dietitians to be aware of the latest scientific literature. The literature increasingly indicates that healthy plant-based nutrition is essential in the prevention and curative aspect of chronic diseases and conditions such as type 2 diabetes, cardiovascular disease, certain cancers, chronic kidney disease, etc. Also, plant-based nutrition is much more sustainable than animal-based nutrition, so it should become a necessary shift to save the planet.

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