A new study shows that a vegan diet can transform people’s gut microbiome in a more positive way than a vegetarian or a meat-eating diet.
The study, titled “Gut microbiome signatures of vegan, vegetarian and omnivore diets and associated health outcomes across 21,561 individuals,” analysed data from participants in the UK, US and Italy. It was published in Nature Microbiology in January 2025.
The gut microbiome is a complex ecosystem of bacteria critical for breaking down food, releasing nutrients, and regulating immune responses. The study found that different diets lead to different species of bacteria thriving.
Out of the three groups of people studied, vegans had the highest levels of bacteria linked to fibre digestion such as Roseburia hominis and Lachnospiraceae species, which produce short-chain fatty acids, molecules that play a key role in reducing inflammation, strengthening gut barriers and supporting metabolic health.
On the other hand, meat-eaters had bacteria associated with digesting meat such as Ruminococcus torques and Bilophila wadsworthia, which have been linked to higher inflammation and poorer cardiometabolic health outcomes. Vegetarians had microbiomes that fell between these two extremes, not as good as those from vegans.
Professor Tim Spector, study co-author and founder of gut health company ZOE, which was part of the research, said to the Independent, “This study underscores how important diet is in shaping the gut microbiome and our overall health…We found a plant-rich diet, particularly one high in a variety of fruits and vegetables, leads to a healthier microbiome composition, which is important for better health outcomes in the long run, including a reduced risk of chronic diseases.”
The study also found that vegans were more likely to harbour microbes found in soil such as Enterobacter hormaechei, suggesting that fresh fruits and vegetables could introduce beneficial bacteria into the gut.
Diets high in animal products and processed foods tend to favour microbes that produce harmful compounds, such as trimethylamine, which has been associated with heart disease.
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