By Sam Carey, Founder of Run Love Sprint.
Plant-based eating has gone from niche to normal, and it's increasingly common among runners. Ask around at any London run club and you'll find vegetarians, vegans and plenty of people simply eating less meat. But there's still a lingering worry that cutting out animal foods might hold you back, particularly for women, who are more likely to go plant-based and who face specific risks if they don't eat enough. A new review has looked at the evidence, and its conclusion is encouraging, as long as you get a few things right.
The research
The review, Vegetarian diets in female athletes: performance, health outcomes, and the implementation gap (opens in a new tab), was published in Frontiers in Nutrition in August 2026 by Miguel López-Moreno and colleagues at Universidad Francisco de Vitoria in Madrid. It's a narrative review, meaning the authors summarised the available studies rather than pooling their results statistically, and they're upfront that the evidence is still limited, with many small, short or observational studies. It's also worth knowing that the lead author has previously been paid by Danone and a plant-based food company for advisory work, which he discloses and says is unrelated and no longer ongoing.
The main finding
The headline is reassuring. Across the studies they reviewed, the authors found that vegetarian and vegan diets don't in themselves harm women's exercise performance, muscle gains or hormonal health, or raise the risk of the under-fuelling condition known as RED-S, provided their nutritional needs are met.
Several of the studies involved runners. One study of recreational runners in Germany (opens in a new tab) compared vegans, vegetarians and meat eaters and found no difference in exercise capacity or body composition between the groups. Another study included in the review, of physically active women, found similar muscle mass and leg strength in vegans and meat eaters.
It's how you do it, not the label
The most useful idea in the review is what the authors call the implementation gap. Their argument is that many of the problems blamed on plant-based diets are really about how they're followed. A well-planned vegetarian diet and a poorly planned one can look very different on the plate, and the studies that found problems often involved people who simply weren't eating enough, or enough of the right things.
The biggest risk, by some distance, is not eating enough overall. Low energy availability, where you don't take in enough fuel to cover your training and everyday needs, is the root cause of RED-S, which can affect hormones, bone health and recovery, and raise the risk of stress fractures. Plant-based foods are often filling but lower in energy, so it can be easier to under-eat without realising, particularly during heavy training.
The nutrients to keep an eye on
The review highlights a handful of nutrients that need more attention on a plant-based diet:
- Vitamin B12, which isn't naturally found in plant foods in a form the body can use, so you'll need fortified foods or a supplement.
- Iron, because the iron in plants is less easily absorbed than iron from meat. This matters for women runners in particular, who lose iron through periods and training.
- Calcium and vitamin D, which are important for bone health and especially relevant if you're at any risk of under-fuelling.
- Omega-3 fats, as the long-chain forms are largely missing from vegan diets. Algae-based supplements are an option, although the authors note there's little evidence they improve performance.
Signs to look out for
The authors suggest keeping an eye on your menstrual cycle, because changes such as missed or irregular periods can be an early sign that you're not eating enough to support your training. Other warning signs worth taking seriously include persistent tiredness, frequent niggles or injuries that don't heal, and performance that's going backwards despite consistent training.
My take
If you're thinking about eating more plants, the research suggests there's no reason it should hold your running back. The key is to plan it properly. Make sure you're eating enough, especially around harder training, include good sources of protein at each meal, and pay attention to B12, iron, calcium, vitamin D and omega-3s. If you're unsure, or you're training hard on a fully vegan diet, it's worth speaking to your GP about a blood test or getting advice from a registered dietitian. Done well, plant-based running isn't a compromise. It's just another way of fuelling the miles.
This article is for general information and isn't a substitute for advice from your GP or a registered dietitian.
