Scope: Trimethylamine-N-oxide (TMAO), a metabolite linked to the gut microbiota, is associated with excess risk of heart disease. We hypothesized that (i) TMAO response to animal source foods would vary among healthy men and (ii) this response would be modified by their gut microbiome.
Methods and results: A crossover feeding trial in healthy young men (n = 40) was conducted with meals containing TMAO (fish), its dietary precursors, choline (eggs) and carnitine (beef), and a fruit control. Fish yielded higher circulating and urinary concentrations of TMAO (46-62 times; p < 0.0001), trimethylamine (8-14 times; p < 0.0001), and dimethylamine (4-6-times; P<0.0001) than eggs, beef, or the fruit control. Circulating TMAO concentrations were increased within 15 min of fish consumption, suggesting that dietary TMAO can be absorbed without processing by gut microbes. Analysis of 16S rRNA genes indicated that high-TMAO producers (≥20% increase in urinary TMAO in response to eggs and beef) had more Firmicutes than Bacteroidetes (p = 0.04) and less gut microbiota diversity (p = 0.03).
Conclusion: Consumption of fish yielded substantially greater increases in circulating TMAO than eggs or beef. The higher Firmicutes to Bacteroidetes enrichment among men exhibiting a greater response to dietary TMAO precursor intake indicates that TMAO production is a function of individual differences in the gut microbiome.
Keywords: Dietary precursor intake; Gut microbiota; Human; Metabolism; Trimethylamine-N-oxide.
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