Potential Adverse Effects of L Carnitine Marnys L Carnitine: Benefits, Uses, Side Effects, and More Vaginal epithelial dysfunction is mediated by the microbiome, metabolome, and mTOR signaling: Cell Reports 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) 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.