Do Vegans Have Less Diverse Gut Bacteria? 2026 Study

A 2026 University of Copenhagen study compared the gut microbiomes of 75 vegans and 75 omnivores, expecting the plant eaters to come out ahead on every measure. They did not. On average, the vegans had lower gut bacterial diversity than the omnivores, and the researchers think the reason is protein. Vegans got 12% of their energy from protein, omnivores got 17%, and the vegans who ate the most protein had diversity on par with the meat eaters.

That is a surprising twist in the gut-health conversation, where plants usually get all the credit. Here is what the study found, why protein keeps coming up, and what it does and does not mean for how you eat.

What the study actually found

Researchers at the Novo Nordisk Foundation Center for Basic Metabolic Research analysed stool, blood and urine from 75 vegans and 75 omnivorous Danes. The vegans had a generally health-promoting microbiome, but one measure stood out in the wrong direction: the average diversity of their gut bacteria was lower than in the omnivores. Diversity is widely treated as a marker of a resilient gut.

Key Takeaway: A vegan diet was linked to a healthier gut profile overall, but lower average bacterial diversity, which researchers did not expect from a high-fiber way of eating.

Why protein may be the missing piece

The authors point to protein as the likely explanation. Vegans in the study got 12% of their daily energy from protein, compared with 17% for omnivores. That gap tracked with the diversity gap. Crucially, the vegans who ate the most protein had bacterial diversity comparable to the omnivores, which suggests protein, not plants, was the variable doing the work.

Stat: Vegans averaged 12% of energy from protein versus 17% for omnivores, and higher-protein vegans matched omnivores on gut diversity.

This fits a bigger theme in nutrition research: the protein question is more nuanced than "more is always better", and getting enough from the right sources matters as much as the headline number. If you eat plant-based, hitting a solid protein target may do more for your gut than adding yet another serving of greens.

Vegan guts still looked healthy in other ways

It would be a mistake to read this as "vegan diets are bad for your gut." The same vegans had more bacteria that break down dietary fiber, more of an organism called Blastocystis that has been linked to lower blood pressure, and lower blood glucose, lower cholesterol and fewer inflammatory markers than the omnivores. The fiber story that drives trends like fibermaxxing still holds up here.

Key Takeaway: The vegans had lower blood sugar, lower cholesterol and less inflammation, so lower diversity was one weak spot in an otherwise favorable profile.

What this might mean for your plate

If you eat mostly or entirely plant-based, the practical read is to treat protein as a priority rather than an afterthought. Lentils, beans, tofu, tempeh, edamame, soy and seitan all push your protein intake up while keeping fiber high. Variety matters too, since different plants feed different microbes. The goal is not to eat less plant food but to make sure protein is not quietly falling short.

Tracking helps here, because plant protein is easy to underestimate across a day. Knowing roughly how much you are getting, and from how many different sources, turns a vague intention into something you can actually adjust. The same logic applies whether you are vegan or omnivore: where your protein comes from and when you eat it is worth paying attention to.

The caveats worth keeping

This was a small, observational study of 150 people in Denmark. It compares existing diets rather than assigning them, so it can show associations but cannot prove that low protein directly shrinks gut diversity. The lead researcher, Oluf Borbye Pedersen, was clear that the findings do not support firm dietary recommendations yet. Treat it as a useful signal, not a verdict.

Key Takeaway: The study shows a link, not cause and effect, so see it as a reason to watch your protein, not proof that plant-based eating harms your gut.

Sources

FAQ

Do vegans have less diverse gut bacteria? In a 2026 Copenhagen study of 150 people, vegans had lower average gut bacterial diversity than omnivores. The researchers linked this to lower protein intake, since vegans eating the most protein matched omnivores on diversity. It was one weak spot in an otherwise healthy vegan gut profile.

Why would a high-fiber vegan diet lower gut diversity? The study suggests protein, not fiber, was the key difference. Vegans got 12% of energy from protein versus 17% for omnivores, and that gap tracked with the diversity gap. Fiber still fed beneficial fiber-degrading bacteria, so the issue appears specific to protein intake.

How much protein should a vegan eat for gut health? The study does not set a target, and it cannot prove protein causes higher diversity. It does suggest that vegans eating more protein had diversity similar to omnivores. Prioritising protein-rich plants like legumes, tofu, tempeh and soy is a reasonable, evidence-aligned approach.

Is a vegan diet bad for your gut? No. The same vegans had lower blood sugar, lower cholesterol, fewer inflammatory markers and more fiber-degrading bacteria. Lower diversity was a single weak spot in an otherwise favorable profile, and the study was observational, so it cannot establish harm.

-- Selena