People who eat more plant-based and less meat-based foods — whether on a vegan, vegetarian, or omnivorous diet — have more favourable microbiome compositions than those who did not follow a healthy dietary pattern, new research published in Nature Microbiology suggests.
For example, while red meat was found to be a strong driver of omnivore microbiomes, it has corresponding signature microbes that are negatively correlated with cardiometabolic health. In contrast, the signature microbes found in vegans’ gut microbiomes were correlated with favorable cardiometabolic markers and were enriched in omnivores who ate more plant-based foods.
“From the viewpoint of the impact of diet on the gut microbiome, what seems to be more important is the diversity of healthy plant-based foods that are consumed,” principal author Nicola Segata, PhD, University of Trento, Trento, Italy, told Medscape Medical News. “Whether this comes within a vegan or an omnivore diet is less crucial, as long as there is no specific overconsumption of unhealthy food categories, such as red meat.”
Excluding broad categories of foods also can have consequences: for example, the exclusion of dairy fermented foods is associated with decreased presence of potentially probiotic microbes, while avoiding meat or dairy products does not necessarily have a positive effect if it does not also come with a variety of quality plant-based products.
The researchers analysed biological samples from 21,561 individuals to map how differences in diet patterns (omnivore, vegetarian, and vegan) are reflected in gut microbiomes. They found that the three diet patterns are highly distinguishable by their microbial profiles and that each diet has corresponding unique signature microbes, including those tied to digestion of specific types of food and sometimes those derived from food itself.
The microbiomes of omnivores had an increased presence of bacteria associated with meat digestion and also had more bacteria associated with both inflammatory bowel disease and increased colon cancer risk. The microbiomes of vegans had an abundance of bacteria involved in fiber fermentation, which help produce short-chain fatty acids. These compounds have beneficial effects on gut health by reducing inflammation and helping to maintain a better homeostatic balance between an individual’s metabolism and immune system.
So, according to the authors, by eating more plant-based foods, people with an omnivorous diet can bring the proportion of beneficial signature microbes in their microbiomes more in line with the levels in people who are vegan or vegetarian. “Since our data showed that omnivores on average ingest significantly fewer healthy plant-based foods than vegetarians or vegans, optimizing the quality of omnivore diets by increasing dietary plant diversity could lead to better gut health,” they wrote.
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