Fish diet tied to circulating trimethylamine-N-oxide concentration

Plasma trimethylamine-N-oxide (TMAO) concentration is linked with fish intake but not with red meat consumption, while an unhealthy plant-based diet index (uPDI) is inversely associated with TMAO concentration, reveals a study.

Elevated concentrations of TMAO, a compound found in seafood and produced through human gut microbial metabolism of its precursors, have been previously suggested to increase the risk of cardiovascular events, according to the investigators.

Dietary predictors were identified by examining TMAO concentrations in two fasting plasma samples collected 6 months apart among 620 healthy men. Short- and long-term dietary intakes were evaluated during the same period of blood collections via repeated 7-day dietary records (7DDRs) and a semiquantitative food-frequency questionnaire (SFFQ), respectively.

Then, the investigators classified individual food items into 21 groups and regressed against averaged TMAO concentrations. They also examined the relationship between dietary scores and TMAO concentrations.

In adjusted models, SFFQ assessments of fish and egg intakes significantly correlated with higher TMAO concentration (β, 0.082, 95 percent confidence interval [CI], 0.021–0.14; p=0.009 for fish; β, 0.065, 95 percent CI, 0.004–0.13; p=0.039 for egg). Such association was also found in the 7DDR assessments (β, 0.12, 95 percent CI, 0.060–0.18; p<0.001).

No association was found between red meat intake and TMAO concentrations. Moreover, TMAO concentrations were inversely associated with uPDI (β, –0.013, 95 percent CI, –0.021 to –0.005; p=0.001) and positively correlated with healthy dietary scores.

“As such, this study suggests that in free-living populations, higher circulating concentrations of TMAO cannot simply be interpreted as a marker of unhealthy food intake or an unhealthy dietary pattern,” the investigators said.