The number of vegans has been steadily increasing over the decades. While it’s hard to find exact numbers, an estimated 1-4% of people in Europe and North America follow a vegan diet.
One of the reasons many people go vegan is for its potential health benefits. Compared to a standard diet--which is often loaded with processed junk foods--the vegan diet does have some health benefits.
But what about endurance athletes–Is the vegan diet beneficial or harmful for performance? Let’s dive into this.
Note: Many athletes choose a vegan diet completely for moral reasons. Here, we are going to ignore the moral arguments and only focus on the vegan diet from the lens of endurance nutrition.
How Many Endurance Athletes Are Vegan?
It’s very difficult to get accurate information about how many endurance athletes are vegan. The data primarily comes from self-reported surveys, and many athletes change their diets. However, it is clear that veganism is becoming more popular amongst athletes.
For example, a survey of athletes competing in the 2024 Paris Olympics found that 5% identified as vegan or vegetarian. As for endurance athletes, one survey of marathoners found that 10% were vegan or vegetarian. The actual numbers are likely lower, but it still shows a growing trend of plant-based diets with athletes.
The Influence of Prominent Vegan Athletes
Many renowned endurance athletes follow a vegan, proving that it is possible to perform at an elite level while following plant-based nutrition.
Some of these athletes even attribute the vegan diet to their success. Because of their elite status, when they extol the benefits of the vegan diet for performance, it influences others to take up the vegan diet.
List of Notable Vegan Endurance Athletes
- Scott Jurek - Ultramarathon legend and holder of multiple records, including the fastest Appalachian Trail completion.
- Fiona Oakes - Marathon runner and world record holder with numerous championship victories.
- Harriett Kjaer - Ultra-trail runner whose list of accomplishments includes running for 59 hours with only one hour of sleep.
- Dotsie Bausch - Cyclists with an Olympic silver medal, eight U.S. national championships, two Pan American gold medals and a world record.
- Christine Vardaros - Professional cyclocross racer with many wins, including the Santa Cruz Classic.
- Molly Cameron - Professional cyclocross racer with multiple championships and strong performances in international races.
- Hillary Biscay - Ironman triathlete and US Olympic Trials Qualifier.
- John Joseph - Ironman triathlete who notably overcame many personal obstacles on his path towards athletic success.
- Brendan Brazier - Ironman triathlete and ultrarunner who has written several books on the benefits of veganism.
- Morgan Mitchell - Track and field athlete who competed in the 2016 and 2021 Olympics.
- Rich Roll: Ultra-endurance athlete and named one of the '25 Fittest Guys in the World' by Men's Fitness Magazine in 2009
- Novak Djokovic - Record-breaking tennis champion and 24-time Grand Slam winner.
Not All Athletes Have Success on the Vegan Diet
While many athletes are successful on the vegan diet, it’s worth noting that many athletes who switched to veganism experienced drops in performance. World champion freerunner Tim Shieff is one example. After switching to the vegan diet, he experienced fatigue and poor recovery, so went back to eating animal products.
Can the Vegan Diet Improve Athletic Performance?
While there are some studies which found vegan athletes had better endurance than omnivores, these studies were very limited. Overall, there is almost no data that shows the vegan diet can improve athletic performance.
Rather, the research mostly shows that it is possible to follow a vegan diet without impairing performance or adaptation–but much more careful planning will be needed than if following a less-restrictive omnivore diet.
Potential Problems for Endurance Athletes Following a Vegan Diet
1. Too Much Fiber
A lot of foods that make up a typical vegan diet are high in fiber. Think leafy green vegetables, whole-grains, and fresh fruits. These foods can help vegans meet their daily intake requirements for nutrients like iron, magnesium, and certain vitamins without having to consume animal products.
While many people in the general population could benefit from increasing fiber intake, too much fiber can be detrimental for endurance athletes.
It can remain in the gut, causing digestive issues during exercise. Fiber also reduces appetite. While this is a benefit for most people, it could cause an athlete to consume inadequate amounts of calories and create an energy deficit.
For more info about fiber, read our Guide to Carbohydrates.
Nduranz fueling drinks and gels are vegan-friendly and contain absolutely no fiber.
2. Essential Amino Acid Challenges
There are many plant-based sources of protein that vegan athletes can consume. However, generally speaking, plant proteins are inferior to animal proteins. Plant proteins typically have:
- Poorer digestibility: The presence of antinutrients, enzyme inhibitors, and fiber can inhibit digestion. As a result, plant proteins tend to have a lower digestibility score than animal proteins.
- Incomplete amino acid profile: Most plant proteins do not contain all essential amino acids. Leucine is considered especially of concern for vegan athletes.
- Fiber: Many unprocessed plant proteins are high in fiber, which can cause digestive issues for endurance athletes.
These problems can be solved by eating more proteins and combining different plant proteins to get a full amino acid spectrum. However, it takes much more planning than using animal based proteins such as whey.
3. Micronutrient Deficiencies
The good news is that plant food is rich in micronutrients. However, the vegan diet is lacking in certain important micronutrients. These include:
Vitamin B12
Vitamin B12 plays a crucial role in red blood cell production, nerve function, and DNA synthesis—functions essential for endurance athletes. Without adequate B12, athletes may experience fatigue, neurological issues, and anemia, all of which can hinder performance.
Since B12 is not naturally found in plant-based foods, vegan endurance athletes must rely on fortified foods or supplements to meet their daily requirements. Regular blood tests are recommended to monitor B12 levels, ensuring optimal performance. For better absorption, athletes should choose a supplement containing methylcobalamin, the more bioavailable form of B12, and take it consistently.
Iron
Many plant foods like kale, beans, and quinoa are rich in iron. However, it’s the non-heme form or iron, which is less readily absorbed by the body compared to the heme iron found in animal products.
Endurance athletes, especially females, have higher iron demands because of the physical stress of long-duration exercise. Because of this, vegan athletes should regularly monitor their blood iron levels and may need to take iron supplements.
Vitamin D
Vitamin D is vital for bone health, immune function, and muscle performance—key factors in endurance sports. Although the body can produce vitamin D through sunlight exposure, many vegan athletes may struggle to meet their needs, particularly during the winter months or in areas with limited sunlight.
Additionally, most plant-based foods provide very little vitamin D, and the form they contain (D2) is less effective at raising blood levels compared to the D3 found in animal sources. For optimal performance, vegan endurance athletes may need to supplement with vitamin D, especially during months of limited sun exposure.
The Verdict?
Whether or not the vegan diet hinders or helps endurance performance is still unclear. However, what is clear is that vegan athletes will need to pay careful attention to their nutrition–even more so than omnivore athletes–in order to maintain performance.
If you are considering a vegan diet, follow these guidelines:
- If possible, consult a sports nutritionist.
- Avoid any major diet changes during periods of intense activity.
- Go slowly and pay attention to your body’s response.
- Monitor for nutrient deficiencies.
For more on the vegan diet for endurance athletes, watch this episode of the Nduranz podcast. Dr. Tim Podlogar and Alex Rhodes talk to Tim Allen about his experience with the vegan diet.
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