Studies have shown that Trimethylamine-N-oxide (TMAO)—a gut-microbiota-dependent cardiovascular risk factor—increases with beef- and fish-, but not poultry-ingestion, while its connection with pork remains unclear. Also, the effect of pork-ingestion on the human microbiome, in general, is poorly understood. Knowledge of relative TMAO-effects of different animal-proteins may assist guidelines for habitually high-meat-consuming populations.


We investigated the impact of pork consumption on microbiota-mediated circulating TMAO response (primary endpoint) in otherwise healthy omnivores at-risk for cardiovascular disease due to middle and older age and overweight. Secondary outcomes included microbiota features, trimethylamine and its dietary precursors, 346 other biogenic amines, and pre-disease cardiovascular risk indicators such as blood lipids, proinflammatory and oxidative stress markers. Also, we exploratively examined the microbiota signatures of different TMAO-producing phenotypes.


In this randomized, controlled, all-food-provided, 2-arm crossover, non-inferiority, trial, adults aged ≥50 years (n=38/arm) consumed 156 g/day of lean pork or chicken as primary proteins as part of the recommended American diet. Since poultry is recommended as a heart-healthy animal-protein, a food- and nutrient-matched chicken-diet was the active control for the pork-diet.


Unlike extrapolating negative results, we show for the first time that dietary pork is non-inferior to chicken for TMAO response and microbiota-generated essential TMAO-precursor—trimethylamine (both, 97.5% CI). Blood pressure, atherosclerotic cardiovascular risk score, markers of lipid metabolism (triglycerides, LDL-C, HDL-c, cholesterol), inflammation (c-reactive protein) and oxidative stress (myeloperoxidase), serum levels of betaine, choline, L-carnitine, composition and functional-capability of the microbiota, and association of baseline TMAO-levels with TMAO-response (both, r>0.6, p=0.0001, biogenic amine profiles by partial least squares-discriminant analysis, were non-distinguishable between the protein groups. TMAO reduction and similar shifts in microbiota and biogenic-amine signatures post-diet in both groups indicate a background DGA-effect. Exploratory analyses (not originally proposed) showed, differential baseline circulating TMAO concentrations associated with altered microbiota features (all, FDR corrected p<0.05), hypercholesterolemia risk (p<0.05), and TMAO response (p=0.0001), independent of the dietary proteins.


Validating our original hypothesis that lean pork minimally impacts the gut microbiota and microbiota-dependent TMAO response in omnivores, the study provides the first one-on-one comparison of pork and chicken interventions—two popular animal-proteins—for microbiome-induced proatherogenic TMAO responses. The results indicate that lean pork may be incorporated as a predominant protein within a healthy omnivorous diet without an adverse impact on TMAO-related cardiovascular risks. Follow-up considerations of TMAO-phenotypes may assist cardiovascular risk assessment. The trial was registered at as NCT03539666.