Healthy According to a randomized, double blind, placebo controlled clinical trial published in Elsevier journal Research in Autism Spectrum Disorders (2013), l carnitine supplementation demonstrated a significant therapeutic benefit in children L Carnitine The Right Way to Take L Carnitine to Boost Your Training 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.