# TMAO (Trimethylamine-N-oxide)

TMAO (trimethylamine-N-oxide) is a small compound your gut bacteria help make. They convert dietary choline, phosphatidylcholine, and L-carnitine (abundant in red meat, eggs, and fish) into trimethylamine (TMA). Your liver then oxidizes TMA into TMAO, using enzymes called flavin-containing monooxygenases (mainly FMO3). High blood TMAO has been linked to more heart attacks and strokes, atrial fibrillation, and death from all causes, across several large studies. And mouse work suggests it blocks reverse cholesterol transport and helps form artery-clogging foam cells. But it is complicated. Eating fish, which is generally heart-healthy, also raises TMAO. And your TMAO depends heavily on your gut microbes, your genes (FMO3 variants), and how well your kidneys clear it. So TMAO is best seen as a marker of exposure and microbial activity, not a clean causal risk factor.

## Sources

- Koeth RA, Wang Z, Levison BS, Buffa JA, Org E, Sheehy BT, et al.. (2013). Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis. Nature Medicine. https://doi.org/10.1038/nm.3145
- Wang Z, Klipfell E, Bennett BJ, Koeth R, Levison BS, Dugar B, et al.. (2011). Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease. Nature. https://doi.org/10.1038/nature09922

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_Canonical: https://longevity-switzerland.com/en/glossary/tmao · Part of Longevity Cities · Updated 2026-06-22_