Carnitina Metabolon Does L carnitine cause fishy body odor? Surprising Truth and Solutions Tonum La L carnitina es el suplemento estrella para perder peso: esto es lo que nos dice la ciencia sobre sus efectos Trimethylaminuria: FMO3 mutations that cause malodorous body odor 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.