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The team from the University of Trento (Italy) engaged 21,561 volunteers in their research. This robust sample size allowed scientists to explore the connection between diet and gut microbiome health.
They also found that, regardless of which diet someone follows, one factor stands out as crucial for a healthy microbiome. More on that later.
What Did the Researchers Learn?
During the study, the team analyzed biological samples from the volunteers, identified key differences in their dietary patterns, and mapped how those patterns affect gut bacterial diversity.
“Diets that include or exclude major food groups — such as meat, dairy, fruits, and vegetables — leave a clear mark on the gut microbiome,” the team wrote. “We found significant changes in the microbiomes of vegans, vegetarians, and omnivores, linked to several characteristic microbes.”
While vegans and vegetarians tended to follow healthier diets, omnivores had more diverse microbiomes. But different bacteria affect gut and overall health in different ways, and not all of them are beneficial.
Each dietary pattern showed a unique microbial signature. The gut microbiomes of omnivores contained higher levels of bacteria associated with meat digestion, particularly Alistipes putredinis. That greater diversity also included bacteria such as Ruminococcus torques and Bilophila wadsworthia, which have been linked to inflammatory bowel disease, heart disease, and certain cancers.
The microbiome of vegans was rich in bacteria that ferment fiber; some of these help produce short-chain fatty acids like butyrate. Those compounds reduce inflammation and support healthy metabolism and immune function.
Vegetarians showed higher levels of Streptococcus thermophilus, a bacterium associated with dairy products. Streptococcus thermophilus is used in yogurt production and may influence certain gut toxins, as reported by ILFScience.
One key finding held across omnivores, vegetarians, and vegans: without a diet rich in plant-based foods—especially high-fiber plants—no one achieved a healthy level of microbiome diversity.
Professor Nicola Segata, the study’s lead author, said, “We noticed that the quantity and variety of plant-based foods have a very positive impact on the microbiome. Abandoning meat or dairy products does not necessarily yield positive effects if it is not accompanied by the consumption of a diverse range of quality plant foods.”
The results of the study were published in the journal Nature Microbiology.
