L Carnitine: Benefits, Side Effects, And Dosage, Per Dietitians L carnitine is a naturally occurring amino acid structure that is made in the human brain, liver, and kidneys. L carnitine plays a critical role in energy production, as it converts fat into energy. Supplements don't replace the workbut they can support it L Carnitine helps your body turn fat into usable energy, so you can push harder and recover better. Consistency first. Supplements second. Results Does L Carnitine Work to Help with Erectile Dysfunction?