Carnitine Deficiency: What Is It, Causes, Symptoms, and More Osmosis Trimethylaminuria (Fish Odor Syndrome or TMAU) 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 Full article: Trimethylamine N oxide formation, the bacterial taxa involved and intervention strategies to reduce its concentration in the human body Scientists make breakthrough in studying the enzyme involved in fish odor syndrome