As a trimethylamine and part of the head group of phosphatidylcholine, metabolized by gut microbiota, choline converts to trimethylamine (TMA). Catalyzed by hepatic flavinmonooxygenases, TMA is rapidly oxidized to generate trimethylamine-N-oxide (TMAO), which is proatherogenic and associated with cardiovascular risks. It is confirmed in a large cohort that TMAO is a predictor of cardiovascular risk. It is also supposed that other dietary nutrients with a trimethylamine structure may also generate TMAO from gut microbiota and accelerate atherosclerosis.