Potential Adverse Effects of L Carnitine Marnys 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. Stabilizing the enzyme in fish odor syndrome 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. Fish odour syndrome CMAJ