Objective: Meat intake is suggested to affect gut microbiome composition and the risk of chronic diseases. We aimed to identify meat-associated gut microbiome features and their association with host factors.

Design: Gut microbiota species were profiled by deep shotgun metagenomics sequencing in 9669 individuals. Intake of white meat, unprocessed red meat, and processed red meat was assessed using a food frequency questionnaire. The associations of meat intake with alpha-diversity and relative abundance of gut microbiota species were tested using linear regression models with adjustment for dietary fiber intake, body mass index, and other potential confounders. Meat-associated species were further assessed for association with enrichment of microbial gene function, meat-associated plasma metabolites, and clinical biomarkers.

Results: Higher intake of processed red meat was associated with reduced alpha microbial diversity. White meat, unprocessed, and processed red meat intakes were associated with 36, 14, and 322 microbiota species, respectively. Species associated with processed red meat were enriched for bacterial pathways like amino acid degradation, while those negatively linked were enriched for pathways like homoacetogenesis. Furthermore, species positively associated with processed red meat were to a large extent associated with reduced trimethylamine N-oxide and glutamine levels but increased creatine and carnitine metabolites, fasting insulin and glucose, C-reactive protein, apolipoprotein A1, and triglyceride levels and higher blood pressure.

Conclusion: This largest to date population-based study on meat and gut microbiota suggests that meat intake, particularly processed red meat, may modify the gut microbiota composition, functional capacity, and health-related biomarkers.