L Theanine Vs L Carnitine: Can We Combine Them? Vinatura Supplements 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. 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. Stabilizing the enzyme in fish odor syndrome 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)