Plant-Based Diets and Endurance: There Is an Aerobic Benefit, but Don't Rush to Conclusions
A meta-analysis of 10 studies found a moderate advantage for plant-based diets in aerobic measures and no loss in strength. But the overall performance figure came out at zero — we look at why that happened.
The question "can you run marathons without meat" stopped being theoretical long ago: plant-based eating shows up both in the peloton and on ultramarathon podiums. But there is a big difference between individual examples and data. A meta-analysis pooling the available comparisons gives an unexpectedly intriguing picture: it boils down neither to "plant-based is better" nor to "plant-based is worse".
What was compared
The systematic review with meta-analysis included 10 studies and 293 participants. Plant-based diets — vegan and lacto-ovo-vegetarian — were compared with omnivorous ones.
One caveat right away, important for interpretation: these are mostly observational comparisons of groups, not randomization of people into diets for months at a time. People choose how they eat for themselves, and along with the diet they bring a whole train of other habits.
Three results that have to be read together
Aerobic measures: a moderate plus. Effect size 0.55 (95% CI 0.29–0.81, p < 0.05) in favour of plant-based diets. In the subgroup of strictly vegan diets it was similar, 0.66.
Strength and power: no difference. Effect size −0.30 (95% CI from −0.67 to 0.07, p > 0.05) — statistically non-significant. In the vegan subgroup it was practically zero (−0.07). The main fear that "strength will drop without meat" is not supported by the data.
Overall performance: zero. The pooled figure is 0.01 (95% CI from −0.21 to 0.22).
This combination is the most interesting part. How does an aerobic plus of 0.55 coexist with an overall zero? There is no sleight of hand here: different measures were pooled into different groupings, and when aerobic and strength outcomes are added together, the positive shift in one is cancelled out by the zero and slightly negative shift in the other. The conclusion is simple and honest: the advantage, if it exists, is narrow — it lies in the aerobic domain, not in "performance in general".
Separately: body mass index was lower among those following plant-based diets — an effect of −0.27 (95% CI from −0.40 to −0.15, p < 0.05), small but significant.
Why it is easy to go wrong here
BMI is exactly what points to the main interpretation problem. Lower body mass by itself improves relative aerobic measures — VO₂max is calculated per kilogram. That means part of the "plant-based diet advantage" may simply be the effect of a lighter athlete, not a property of the food itself.
Next comes classic confounding. People who choose plant-based eating tend to pay closer attention to their health overall: less alcohol, more vegetables and fibre, more deliberate sleep and routine. An observational design does not allow the contribution of the diet to be separated from the contribution of everything else in their lifestyle.
The authors honestly list their limitations too: there are few studies, which is why men and women could not be compared separately, and the analysis did not distinguish whether participants took supplements or not. And that last point matters fundamentally: some of the potential deficiencies of a plant-based diet are covered precisely by supplements, and if they were in play, we are not measuring the "pure" diet.
What to watch if you are making the switch
The practical part is not about performance but about not creating a problem for yourself.
- B12 is non-negotiable: on a vegan diet it comes only from supplements or fortified foods. A deficiency hits the blood and the nervous system.
- Iron. Non-heme iron from plants is absorbed worse than heme iron. For runners, and especially for women, this is a separate risk factor — we have a detailed piece on ferritin.
- Protein. Plant sources are usually lower in leucine and have a poorer amino acid profile, so it makes sense to keep the daily intake closer to the upper end of the endurance range and to spread it across meals.
- Creatine. There is practically none in plant food, and vegans have lower baseline muscle levels — which, incidentally, makes creatine supplementation more effective for them than for omnivores.
- Omega-3. Plant-derived ALA converts to EPA and DHA poorly; on a strict vegan diet it is worth considering an algae-based supplement.
- Calcium and vitamin D — if you are giving up dairy, it is worth counting your intake deliberately, especially given the risk of bone stress injuries in runners.
Key points
- Meta-analysis of 10 studies, 293 participants; vegan and vegetarian diets were compared with omnivorous ones.
- Aerobic measures: a moderate plus, ES 0.55 (CI 0.29–0.81).
- Strength and power: no difference (ES −0.30, non-significant) — the fear that "strength will drop" is not confirmed.
- Overall performance: 0.01, that is, zero. The advantage is narrow, not across the board.
- BMI was lower (ES −0.27) — part of the aerobic advantage may be explained by body mass rather than by diet.
- The design is observational, there are few studies, and supplement use was not accounted for — causality is not proven.
- Making the switch requires attention to B12, iron, protein, creatine, omega-3, calcium and vitamin D.
Sources: “Plant-based diets benefit aerobic performance and do not compromise strength/power performance: a systematic review and meta-analysis”, British Journal of Nutrition. https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/plantbased-diets-benefit-aerobic-performance-and-do-not-compromise-strengthpower-performance-a-systematic-review-and-metaanalysis/4941919C8BC86865A35E56189831D8DF. “Plant-based diets and sports performance: a clinical review”, Sport Sciences for Health, 2023. https://doi.org/10.1007/s11332-023-01074-8. “Plant-Based Nutrition and Supplements for Optimal Athletic Performance”. https://pmc.ncbi.nlm.nih.gov/articles/PMC12586379/