Inverse associations between Mediterranean diet constituents and the gut microbiota in metabolic-associated steatotic liver disease (MASLD): a case-control study

Background Dietary therapy, specifically for weight loss, is currently considered first-line therapy for metabolic-associated steatotic liver disease (MASLD). However, increasing recognition of the role of the gut-liver axis in MASLD highlights potential for microbiota-modulating dietary therapy to improve outcomes. This study aimed to explore dietary variables relevant to gut microbiota in MASLD. Methods Twenty-five adults with MASLD and 25 healthy controls were recruited using a retrospective case-control design and characterised using 3-day dietary intake records, clinical markers, and shotgun metagenomic sequencing. Results MASLD participants consumed less dietary fibre (p = < 0.01), very long chain omega-3 fatty acids (p = 0.02), nuts and seeds (p = 0.03), whole grains (p < 0.01) and vegetables (p = 0.04). Participants with MASLD had lower abundance of Alistipes senegalensis (r=-0.01, p = 0.04), Coprococcus eutactus (r=-0.07, p = 0.006), Faecalibacterium (r=-0.02, p < 0.001), and higher abundance of Ruminococcus torques (r = 0.04, p = 0.02), and less expression of functional pathways associated with ethanol production, methionine, folate and branched-chain amino acid metabolism. Bacterial species and functional pathways more abundant in MASLD were positively associated with intake of added sugars and saturated fat, and negatively associated with unsaturated fatty acid and dietary fibre intake. Conclusions Microbiota characteristics differ between individuals with and without MASLD, and this is influenced by dietary intake. Future translation-focused research investigating dietary interventions and the gut-liver-axis in MASLD are warranted.