Stabilizing the enzyme in fish odor syndrome Does L carnitine cause fishy body odor? Surprising Truth and Solutions Tonum 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. Customer reviews for Nutricost L Carnitine Tartrate Supplement Powder (100 Grams) 1 Gram per Serving; 100 Servings Walmart.com