Scientists make breakthrough in studying the enzyme involved in fish odor syndrome Trimethylaminuria, or fish odour syndrome is an uncommon condition that causes an unpleasant, fishy smell. The body is unable to turn a strong smelling chemical called trimethylamine produced in the gut when Breakthrough in studying the enzyme that ultimately produces fish odour 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. Frontiers The role of trimethylamine N oxide in disease pathogenesis and the therapeutic potential of traditional Chinese medicine Frontiers Gut Metabolite Trimethylamine N Oxide in Atherosclerosis: From Mechanism to Therapy