Cross-sectional comparisons of subgingival microbiome and gingival fluid inflammatory cytokines in periodontally healthy vegetarians versus non-vegetarians

Abstract

Background: Vegetarian diets are known to reduce inflammation. The objective of this study was to test the hypothesis that reduced inflammation associated with a vegetarian diet would promote a more commensal subgingival bacterial profile. Methods: A total of 39 periodontally healthy subjects (PD ≤3 mm, bleeding on probing <10%) were enrolled. Dietary intake was assessed by a food frequency questionnaire. A comprehensive periodontal examination was performed. Gingival crevicular fluid (GCF) and subgingival plaque samples were collected. GCF samples were assessed for interleukin-1β, interleukin-6, interleukin-8, tumor necrosis factor-alpha, and interleukin-10. Plaque samples were analyzed for bacteria using 16S rDNA sequencing on an Illumina platform. GenBank database was used for taxonomy classification. Results: Twenty-three subjects were categorized as vegetarian and 16 non-vegetarians. Clinical periodontal measures and GCF cytokine levels were statistically comparable between the two groups. Measures of microbial richness and alpha diversity were also comparable between the two dietary groups. Vegetarians harbored higher levels of phyla associated with gingival health (Actinobacteria, and Proteobacteria). Two species known to be associated with periodontitis (Mogibacterium timidum and Veillonella rogosae) were prominent in non-vegetarians. Pearson's correlations between GCF inflammatory cytokines and microbial taxa differed between vegetarians and non-vegetarians. In vegetarians, the anti-inflammatory cytokine IL-10 positively correlated with two species known to be associated with periodontal health (Peptidiphaga sp. HMT183 and Rothia aeria). Conclusions: Diet is directly and indirectly associated with the microbial composition of subgingival plaque. A vegetarian diet may promote a subgingival microbiota associated with periodontal health.