Associations Between Diet Quality, Sulfidogenic Colonic Bacteria and Systemic Inflammation

Low quality diets and consuming a Western diet pattern (high saturated fat and animal protein) is associated with increased systemic inflammation and the development of many chronic diseases including cancers. The objective of the present study was to understand the associations between diet quality, levels of sulfidogenic bacteria in healthy colonic mucosa and plasma levels of two proinflammatory cytokines. Ninety-two older adults were analyzed and we hypothesized that diet quality would be inversely related to sulfidogenic bacteria, sulfidogenic bacteria would be positively related to systemic levels of proinflammatory cytokines and sulfidogenic bacteria would mediate the relationship between diet quality and systemic inflammatory markers. The Healthy Eating Index 2015 (HEI-2015) was used to determine diet quality from two 24-hour diet recalls and the cohort was dichotomized into low and high diet quality. Healthy colonic mucosal biopsies were collected during screening and surveillance colonoscopy and analyzed for sulfidogenic specific functional gene targets (pan-dsrA and dsrA-bw) using qPCR. A multiplex cytokine panel was used to assess plasma cytokine levels (Tumor Necrosis Factor-𝝰 (TNF-𝝰) and Interferon-gamma). Contrary to the hypothesis, the present study found moderate inverse associations between diet quality and levels of sulfidogenic bacteria in both right and left colon as well as moderate inverse associations between sulfidogenic bacteria and TNF-𝝰 levels. Additionally, mediation analysis reviewed that the sulfidogenic bacteria indirectly mediated the relationship between diet quality and TNF-𝝰 although the effect was very small. Larger and more controlled studies are needed to understand how diet quality can impact the gut microbiota composition and metabolic behavior and further explore how these changes impact metabolites at the local and systemic level that influence host health and disease.