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Vegans tend to have better gut health than omnivores, according to a new large-scale study by gut health experts including Tim Spector.
Researchers from personalized nutrition app ZOE, co-founded by Spector, and the University of Trento in Italy used stool samples to analyze the gut bacteria of 21,561 participants from multiple countries. There were 656 self-reported vegans, 1,088 vegetarians, and 19,817 omnivores. The researchers used the healthy plant-based diet index (hPDI) to quantify their intake of healthy plant foods. Vegans had a significantly higher hPDI than vegetarians, who had a higher hPDI than omnivores.
Omnivores were found to have the most diverse bacteria in their gut microbiomes. But they also tended to have the highest number of harmful bacteria found to contribute to inflammation, colorectal cancer, and worse cardiometabolic health outcomes.
The vegans, by contrast, had less species diversity but a higher level of beneficial bacteria. These bacteria have been associated with protecting against inflammation and cancer and improved cardiometabolic health.
Signature microbiomes
The study showed that each type of dietary pattern had its own signature. Diets rich in fruits and vegetables produced a higher level of anti-inflammatory bacteria that are specialized in fermenting dietary fibers and resistant starch. This process produces more short-chain fatty acids (SFCAs), which are thought to provide important support for the immune system and brain health.
Read more: Eating A Higher Ratio Of Plant Protein Supports Heart Health, Finds Study
Eating more meat, particularly red meat, and fewer plants produced more harmful bacteria species. These leads to more protein fermentation in the gut, which can cause local and systemic inflammation and the production of fewer SCFAs.
The microbiomes of vegetarians contained bacteria linked to dairy consumption that were absent in the guts of vegans. This was the biggest factor that differentiated vegan and vegetarian microbiomes.
The study also assessed the level of bacteria species from each dietary signature associate with cardiometabolic health. The microbiomes of meat-eaters contained species more commonly linked to poor cardiometabolic health outcomes. By contrast, vegan microbiomes contained species linked to positive markers for cardiometabolic health. Vegetarian microbiomes contained species linked to both good and bad markers.
Increasing consumption of plants
The researchers found that the amount of healthy plant foods consumed was a bigger influence on the health of the gut microbiome than the overall dietary pattern. The omnivorous participants on average ate “significantly fewer healthy plant-based foods” than the vegetarians or vegans.
But if omnivores ate more of these foods, they could increase the number of good bacteria in their guts, according to the study. Tim Spector recommends eating 30 different plant foods a week, including seeds, nuts, and spices, for optimal gut health.
Read more: The 9 Healthiest Fruits, According To Nutritionists
