Are you eating the right plant-based diet?

Not all plant-based diets are good for the body, and adherence to an unhealthful type may negatively affect gut microbiome diversity, composition, and metabolites, suggests a study.

Researchers analysed 705 adults in the Baltimore Longitudinal Study of Aging with available data for diet, faecal microbiome (shotgun metagenomic sequencing), and key covariates. They used data from food frequency questionnaires to obtain healthful plant-based diet index (hPDI) and unhealthful plant-based diet index (uPDI).

PDIs with microbiome α-diversity (richness and evenness measures), β-diversity (Bray–Curtis and UniFrac measures), composition (species level), and plasma trimethylamine N-oxide (TMAO) were examined. Regression models were used to explore the associations before and after adjustment for age, sex, body mass index, education, physical activity, smoking status, and total energy intake.

Of the participants (mean age 71.0 years), 55.6 percent were female, and 67.5 percent were non-Hispanic White. Microbiome α-diversity showed a positive association with hPDI and a negative one with uPDI, driven by microbial evenness (Pielou p<0.05).

In addition, hPDI positively correlated with relative abundance of three polysaccharide-degrading bacterial species (Faecalibacterium prausnitzii, Eubacterium eligens, and Bacteroides thetaiotaomicron) and inversely correlated with six species (Blautia hydrogenotrophica, Dorea sp CAG 317, Eisenbergiella massiliensis, Sellimonas intestinalis, Blautia wexlerae, and Alistipes shahii).

An inverse association also existed between hPDI and TMAO. These associations persisted across age, sex, or race.

“Greater adherence to a healthful plant-based diet is associated with microbiome features that have been linked to positive health, [while] adherence to an unhealthful plant-based diet has opposing or null associations with these features,” the researchers said.