Trimethylaminuria: FMO3 mutations that cause malodorous body odor Dietary supplementation of l carnitine ameliorates metabolic syndrome independent of trimethylamine N oxide produced by gut microbes in high fat diet induced obese mice Food & Function (RSC Publishing) Acetyl L Carnitine: Benefits, Forms, Dosing, and Side Effects Dr Brad Stanfield Scientists make breakthrough in studying the enzyme involved in fish odor 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.