Emerging role of trimethylamine N oxide (TMAO) in colorectal cancer Applied Microbiology and Biotechnology Springer Nature Link 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 Does Carnitine Cause Body Odor? Lume Deodorant 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. 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. Frontiers The role of trimethylamine N oxide in disease pathogenesis and the therapeutic potential of traditional Chinese medicine