A Mediterranean-style eating pattern (MED-EP) may include moderate red meat intake. However, it is unknown if the pro-atherogenic metabolite trimethylamine N-oxide (TMAO) is affected by the amount of red meat consumed with a MED-EP. The results presented are from a secondary, retrospective objective of an investigator-blinded, randomised, crossover, controlled feeding trial (two 5-week interventions separated by a 4-week washout) to determine if a MED-EP with 200 g unprocessed lean red meat/week (MED-CONTROL) reduces circulating TMAO concentrations compared to a MED-EP with 500 g unprocessed lean red meat/week (MED-RED). Participants were seventy-seven women and twelve men (n 39 total) who were either overweight or obese (BMI: mean (30·5) (sem 0·3) kg/m2). Serum samples were obtained following an overnight fast both before (pre) and after (post) each intervention. Fasting serum TMAO, choline, carnitine and betaine concentrations were measured using a targeted liquid chromatography-MS. Data were analysed to assess if (a) TMAO and related metabolites differed by intervention and (b) if changes in TMAO were associated with changes in Framingham 10-year risk score. Serum TMAO was lower post-intervention following MED-CONTROL compared with MED-RED intervention (post-MED-CONTROL 3·1 (sem 0·2) µmv. post-MED-RED 5·0 (sem 0·5) µm, P < 0·001), and decreased following MED-CONTROL (pre- v. post-MED-CONTROL, P = 0·025). Exploratory analysis using mixed model ANCOVA identified a positive association between changes in TMAO and changes in homoeostatic model assessment of insulin resistance (P = 0·036). These results suggest that lower amounts of red meat intake lead to lower TMAO concentrations in the context of a MED-EP.
