Researchers from King’s College London conducted a broad study to explore how vegan, vegetarian, and omnivorous eating patterns influence the gut microbiome. The team enrolled 656 vegan participants and collected stool samples to measure the balance and diversity of gut bacteria. These findings were then weighed against data from approximately 20,000 meat eaters and 1,000 vegetarians, with the study published in Nature Microbiology.
The analysis showed that giving up animal products did not correspond to a clear improvement in gut bacterial balance. Across the groups, the total number and variety of beneficial bacteria were similar, suggesting that diet alone, in the absence of overall dietary quality, does not automatically enhance the gut microbiome.
Further, the study found that vegans who consumed a lot of ultra-processed snacks tended to have lower levels of advantageous gut bacteria. In contrast, incorporating a higher intake of vegetables into the diets of meat eaters was associated with a more balanced microbiota, underscoring the impact of whole-food plant components on gut health.
Researchers highlighted that beneficial gut bacteria produce short-chain fatty acids that help reduce inflammation in the intestine and throughout the body, potentially lowering the risk of heart disease and stroke. This mechanism links microbial balance with broader health outcomes, reinforcing the idea that gut health plays a role in chronic disease risk for diverse dietary patterns.
Earlier work pointed to a range of nutrients thought to protect against colon cancer. The current findings emphasize the ongoing importance of plant-based foods and overall dietary patterns in shaping the gut ecosystem and related health effects, rather than relying on any single diet category as a guaranteed path to better gut health.