Diets rich in whole grains, long-chain n–3 fatty acids boost plasma TMAO concentration

A dietary pattern rich in long-chain n–3 fatty acids (LCn3) from marine foods or whole-grain cereals (WGCs) may substantially increase concentrations of plasma trimethylamine N-oxide (TMAO), results of a study have shown.

“These changes mirrored the direct associations between TMAO concentrations and intakes of fish and WGCs, suggesting that TMAO reflects intakes of these healthy foods and, therefore, it is not a universally valid biomarker of cardiometabolic risk independent of the background diet,” the authors said.

This study sought to assess the medium-term effects of diets naturally rich in polyphenols and/or LCn3 or WGCs on cardiometabolic risk factors through an ancillary study performed within two randomized controlled trials (Etherpaths Project and HealthGrain Project).

In the Etherpaths study (n=78), changes in TMAO (8-week minus baseline) were statistically significant for diets rich in LCn3 (1.15±11.58 μmol/L; p=0.007), but not for those rich in polyphenols (–0.14±9.66 μmol/L; p=0.905) or their interaction (p=0.655; 2-factor ANOVA).

In the HealthGrain Study (n=48), changes in TMAO (12-week minus baseline) in the WGC group (0.94±3.58 μmol/L) markedly differed from that in the Refined Cereal group (–1.29±3.09 μmol/L; p=0.037).

Pooled data of participants in the two studies showed direct associations of TMAO concentrations with LCn3, eicosapentaenoic acid (20:5n–3), and protein intake, but not saturated fatty acids, fibre, monounsaturated fatty acids, and polyphenol intake.

Additionally, TMAO was directly associated with the intake of fish, vegetables, and whole-grain products, but not meat, processed meat, and dairy products.

“TMAO has drawn much attention as a marker of several chronic diseases,” the authors said. “Data on the relation between diet and TMAO are discordant and few human intervention studies have assessed causality for this association.”