Plant-based diets linked to healthier gut microbiomes and cardiometabolic benefits in large study

A new study of 21,561 people found that plant-based diets shape healthier microbiomes and have better cardiometabolic outcomes. Omnivore, vegetarian, and vegan diets are gaining popularity and are spotlighted for making a positive impact.

Published in Nature Microbiology, the research finds that red meat consumption drove omnivore microbiomes, negatively correlated with cardiometabolic health. Such microbes include Ruminococcus torques, Bilophila wadsworthia, and Alistipes putredinis.

Vegan signature microbes were linked to better cardiometabolic markers and were also found to flourish in omnivores eating a high amount of plant-based foods. Lachnospiraceae, Butyricicoccus sp., and R. hominis are examples linked to eating fruit and vegetables.

The authors note that diet-specific gut microbes sometimes overlapped with food microbiomes, especially daily microbes (e.g., Streptococcus thermophilus) and typical soil microbes in vegans.

Role of diet on health

The researchers hope their findings will contribute to nutritional interventions and epidemiology. 

“Our work reinforces how humans can shape their gut microbiomes, and by extension, their health, directly through simple dietary choices as well as more indirectly through agricultural and food production practices.” 

“These diet pattern signatures will be important to inform experiments on specific interactions between single microbes (or genes) and food components and are of potential use in a number of areas, including improving (clinical) intervention studies of different diet patterns and epidemiology studies where gut samples, but not detailed diet data, are available.”

Red meat consumption drove omnivore microbiomes, negatively correlated with cardiometabolic health.Recent diet research suggested that body-gut bacteria partnerships may present potential solutions to fatty liver disease and high cholesterol. The authors noted that high-fiber diets had a positive influence on the partnership.

Plant- versus animal-based

The study authors warn that poor diets with low plant-based foods and highly processed foods cause more deaths than any other risk factors. Cardiovascular disease, cancers, and type 2 diabetes are the leading causes of death. Other research backs this while suggesting the benefits of non-industrialized diets.

“The gut microbiome plays an integral role in human health that can be modified by diet. For example, fermentation of otherwise indigestible plant polysaccharides by gut microbes contributes to a healthy, non-inflamed gut barrier and maintenance of gut homeostasis through the production of short-chain fatty acids (SCFAs) and immune system crosstalk,” explain the authors. 

The researchers discovered that polyphenols, which are byproducts of plant secondary metabolism, are found in plants and are known to support good bacteria that improve the gut barrier, reduce inflammation, and block possible pathogens. 

Fermentation of indigestible plant polysaccharides by microbes contributes to a non-inflamed gut barrier and maintenance of gut homeostasis.They add: “A diet rich in animal foods leads to increased protein fermentation, which may result in a leaky mucosa, local and systemic inflammation, and reduced production of SCFAs. For example, the breakdown of certain animal proteins is linked to the synthesis of gut microbial trimethylamine (TMA), which is oxidized in the liver to trimethylamine N-oxide (TMAO). TMAO has been implicated in various (cardio)vascular diseases and is a potential contributing factor in colorectal cancer.”

Diet and environment link 

The researchers also worry about the impact of unhealthy diets on the environment since animal-based foods cause more significant changes than plant-based foods — specifically, on climate, land and freshwater use, and biodiversity.

Scientists recently suggested that replacing meat with plant protein reduces the risk of heart disease. An Oxford study found diets high in this food type lower mortality and disease risks, environmental resource use, and pollution.

Other researchers are warning that eating processed red meat causes an increased risk of dementia and cognitive decline compared with people who eat very little meat. 

For the omnivore gut microbiome, the new study found species generally linked to meat (especially red versus white meat) consumption. 

“These species have been previously implicated in inflammatory diseases such as inflammatory bowel disease, colorectal cancer, and an overall decrease in SCFAs and were more likely to be associated with negative cardiometabolic health outcomes,” they note.

“Diets with high dairy components showed strong signatures of corresponding food microbes, in particular S. thermophilus and several lactic acid bacteria (for example, L. acidophilus, L. paracasei, and L. lactis), which are generally seen as health-associated gut microbial members.”

Strains specific to vegan gut microbiomes specialize in fiber degradation and are called SCFA producers. 

“Vegan gut microbiomes had the highest prevalence of microbes shared with fruits and vegetables. In particular, we observed gut microbes that are shared with plant and soil microbiomes and have agricultural use in promoting plant growth through nitrogen fixation, such as E. hormaechei and some strains of K. pneumoniae,” detail the authors.