Trimethylaminuria (Fish Odor Syndrome or TMAU) Did You Know? Some people report a fishy smell after supplementing with L carnitine. This happens because certain gut bacteria convert carnitine to trimethylamine, a malodorous compound found in rotting fish. Emerging role of trimethylamine N oxide (TMAO) in colorectal cancer Applied Microbiology and Biotechnology Springer Nature Link Full article: Trimethylamine N oxide formation, the bacterial taxa involved and intervention strategies to reduce its concentration in the human body Trimethylamine N Oxide: The Good, the Bad and the Unknown Role of L carnitine in Cardiovascular Health: Literature Review Cureus