Study finds unexpected benefit to plant-based diet

Even temporary shift to more plant-based foods can help boost gut health

Swapping out meat and dairy can do more than just help animals and the planet, according to a new study that shows a vegan diet can transform your gut and metabolism.

The study, which analyzed data from over 21,000 participants in the UK, US and Italy, found that a plant-based diet can reshape the gut microbiome, fostering bacteria that improve health and reducing the risk of chronic diseases such as diabetes and heart conditions.

The research, published in Nature Microbiology, explored the gut microbiomes of vegans, vegetarians, and omnivores, and found that even small dietary changes – such as eating more fruits, vegetables and fiber – can result in meaningful health improvements.

How plant-based diets impact the gut

The gut microbiome – a complex ecosystem of trillions of microorganisms – is critical for breaking down food, releasing nutrients, and regulating immune responses. But, according to the study, what we eat greatly influences which microbes thrive.

Out of the three groups of people studied, vegans, the study found, had the highest levels of bacteria linked to fiber digestion such as Roseburia hominis and Lachnospiraceae species.

These microbes produce short-chain fatty acids, which play a key role in reducing inflammation, strengthening gut barriers and supporting metabolic health.

Omnivores, on the other hand, harboured bacteria associated with digesting meat such as Ruminococcus torques and Bilophila wadsworthia. These microbes have been linked to higher inflammation and poorer cardiometabolic health outcomes, the study noted.

Vegetarians had microbiomes that fell between these two extremes, the research found, benefiting from their partial intake of plant-based foods.

Diet diversity matters more than we think it does and even a temporary shift can help boost gut health, the researchers said. Omnivores who increased their intake of fruits, vegetables, and whole grains showed significant improvements in gut health, showing that even modest dietary changes could yield benefits.

“This study underscores how important diet is in shaping the gut microbiome and our overall health,” professor Tim Spector, study co-author and founder of gut health company ZOE, which was part of the research, said.

“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.”

One intriguing finding of the study is that some gut bacteria may come directly from the food we eat.

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, the study found.

Omnivores and vegetarians had microbes linked to dairy products such as Streptococcus thermophilus, a yogurt and cheese starter culture.

Gut health and chronic disease

The study also highlights the importance of short-chain fatty acids, compounds produced by certain gut bacteria when they digest fiber. These fatty acids have been linked to reduced risk of conditions such as diabetes, cardiovascular disease and even colorectal cancer.

By contrast, 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.

The research comes amid a dietary trend of Veganuary, a campaign that encourages people to try a vegan diet through the month of January. Last year, around 3 per cent of the UK population participated in it, according to YouGov.

In addition to gut health, a shift to a vegan diet has broader environmental benefits. Animal agriculture is a leading driver of deforestation, greenhouse gas emissions, and water use, making plant-based diets a key tool for combating climate change.