Scientists make breakthrough in studying the enzyme involved in fish odor syndrome 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 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. A recurring fishy odor could indicate a larger medical problem.