A cross-sectional study published in 2019 in the Journal of the International Society of Sports Nutrition found no significant exercise capacity differences among 76 male and female German recreational runners consuming a vegan diet (n=24) compared to those consuming lacto-ovo vegetarian (n=26) and meat-containing diets (n=26) (1).
Exercise capacity was measured as maximum power related to body weight and did not differ significantly between the groups, even though researchers noted some differences in nutrient intakes.
Vegans consumed significantly higher amounts of carbohydrates, fiber, magnesium, iron, folate, and vitamin E, and significantly less dietary fat and vitamin B12, compared with lacto-ovo vegetarians and omnivores. Total calorie and protein intake did not differ significantly between the groups. Calcium intake was below the daily value (1,300 milligrams) for all groups and vegans had the lowest intake (903 ± 554 milligrams). The article did not say if or how much calcium came from fortified foods.
Nutrient intake was assessed via self-reported 24-hour recall, which should be taken with a grain of salt as this is a small snapshot of intake with questionable reliability. It also excluded supplement intake so is not a reliable representation of vitamin B12 intake among the vegans, assuming some were taking supplemental vitamin B12.
In summary, this small study found that eating vegan did not confer any significant advantage or disadvantage in a group of German recreational runners.