[1][2] In animals, TMAO is a product of the oxidation of trimethylamine, a common metabolite of trimethyl quaternary ammonium compounds, like choline, trimethylglycine, and L-carnitine.

In general, the bodies of animals living at great depths are adapted to high pressure environments by having pressure-resistant biomolecules and small organic molecules present in their cells, known as piezolytes, of which TMAO is the most abundant.

[11][12] TMAO can be synthesized from TMA by treatment with hydrogen peroxide:[13] The dihydrate is dehydrated by azeotropic distillation from dimethylformamide.

This suggests competing mechanisms of TMAO on proteins, which accounts for hydrophobic swelling, backbone collapse, and stabilization of charge-charge interactions.

Trimethylamine then accumulates and is released in the person's sweat, urine, and breath, giving off a strong fishy odor.

[citation needed] High circulating TMAO concentrations are associated with an increased risk of all-cause mortality.