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. Trimethylamine N Oxide in Aquatic Foods Journal of Agricultural and Food Chemistry Trimethylamine and Trimethylamine N Oxide, a Flavin Containing Monooxygenase 3 (FMO3) Mediated Host Microbiome Metabolic Axis Implicated in Health and Disease Drug Metabolism and Disposition Potential Adverse Effects of L Carnitine Marnys Carnitine Deficiency: What Is It, Causes, Symptoms, and More Osmosis