Full article: Trimethylamine N oxide formation, the bacterial taxa involved and intervention strategies to reduce its concentration in the human body Carnitine Deficiency: What Is It, Causes, Symptoms, and More Osmosis L carnitine supplements can cause a fishy odor in the breath, sweat, and urine. This is likely due to the formation of trimethylamine (TMA). TMA is also responsible for the pungent smell of Trimethylaminuria (Fish Odor Syndrome or TMAU) Frontiers Trimethylamine N Oxide Pathway: A Potential Target for the Treatment of MAFLD