Plant-Forward Diets Lower Circulating TMAO in Adults: A Systematic Review and Meta-Analysis

Diet modulates circulating trimethylamine N-oxide (TMAO), a gut microbiota-derived metabolite linked to cardiovascular risk; whether plant-forward versus animal-based dietary patterns consistently influence TMAO concentrations in adults remains unclear. A PRISMA-2020-compliant systematic review and meta-analysis (PROSPERO: CRD420261326106) was conducted through February 2026 across multiple databases; eligible studies assessed dietary patterns, food groups, or diet-related interventions in relation to circulating TMAO in adults. Random-effects meta-analyses were performed where data were combinable. Thirty-four studies were included; 11 contributed to quantitative synthesis. Eight RCTs showed significantly lower TMAO with plant-forward versus animal-based exposures (pooled MD −1.08 µM, 95% CI −1.52 to −0.65; I² [a measure of between-study heterogeneity] = 0%), consistent across dietary-pattern (−0.85 µM) and food-group subgroups (−1.24 µM). Three cross-sectional studies linking higher meat intake to higher TMAO showed substantial heterogeneity (I² = 75%). Plant-forward diets are associated with lower circulating TMAO in adults, with the strongest evidence from RCTs.