The Role of l Carnitine in Mitochondria, Prevention of Metabolic Inflexibility and Disease Initiation 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. Does Carnitine Cause Body Odor? Lume Deodorant L carnitine: Science Backed Benefits, Risks, and More 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.