Ronnie Coleman L Carnitine Liquid Nutriride Does L carnitine cause fishy body odor? Surprising Truth and Solutions Tonum L Carnitine: Everything You Need to Know If you are like a lot of people, you may have never heard of carnitine but this important nutrient is critical for our body's ability to optimally burn fat required for energy. 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.