A plant-based diet has been linked to a decreased risk of cardiovascular disease. However, its relationship with gut microbiota had not been thoroughly researched in heart failure (HF) populations, and the mechanisms connecting food to improved outcomes in HF patients remained unknown. A cross-sectional study of 152 individuals with NYHA class I-IV HF with a decreased ejection fraction was performed. A food frequency questionnaire was used to examine the diet. The A Priori Diet Quality Score (APDQS) was used to measure plant-centered diet quality. The APDQS was categorized into quintiles; high scores were characterized by increased intake of nutritionally-rich plant foods and reduced consumption of high-fat meats and unhealthy plant foods. Stool samples were sequenced for the 16S rRNA gene. Linear regression and permutational multivariate analysis of variance (PERMANOVA) were used to assess the APDQS’s associations with alpha (Shannon Index and Inverse Simpson) and beta diversity (measured by the Bray-Curtis dissimilarity index). In addition, the APDQS and the relative abundance of certain taxa at the phylum and genus levels were studied using negative-binomial regressions in DESeq2. The false discovery rate was used to make adjustments for multiple comparisons.

The mean Shannon Index and Inverse Simpson values were 6.28±0.5 and 407.7±183.37, respectively. The APDQS (per 12 units) was linked with a greater Shannon Index (0.13±0.05; P for slope=0.007) and Inverse Simpson (46.87±15.5; P for slope=0.004) among patients aged ≥ 61y after multivariable correction; no relationships were detected among those aged ≥ 61y (P for interaction <0.05 for each). Beta-diversity was not linked with APDQS quintiles (PERMANOVA, P=0.54). The highest quintile of the ADPQS was related to an increased abundance of Enterobacter and a lower abundance of Catenibacterium at the genus level (vs. the lowest quintile). In younger HF patients, eating nutrient-dense plant-based diets was linked to greater gut microbiota diversity, as well as a significantly higher or lower abundance of certain bacterial taxa at the genus level.