Revisiting the Role of Carnitine in Heart Disease Through the Lens of the Gut Microbiota 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. L Carnitine: Everything You Need to Know Trimethylaminuria: Definition, symptoms, and more Ever heard of Fish Odor Syndrome? Its a rare condition where the body cant break down trimethylamine a compound found in foods like fish, eggs, and beans. This leads to a strong, fish like smell Trimethylamine N Oxide: The Good, the Bad and the Unknown