Frontiers Trimethylamine N Oxide Pathway: A Potential Target for the Treatment of MAFLD Does L carnitine cause fishy body odor? Surprising Truth and Solutions Tonum 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: Understanding and Treating Fish Odor Syndrome Full article: Trimethylamine N oxide formation, the bacterial taxa involved and intervention strategies to reduce its concentration in the human body