L Carnitine plays an important role in the larger metabolism equation: helping your body use fat efficiently as fuel. Learn more about the science on this week's post on The Wellness Edit. L Carnitine: Benefits, Uses, and Side Effects Lifespan Research Institute L Carnitine Nadara Clinic L Carnitine Erectile Dysfunction: What the Evidence Actually Shows Carnitine Deficiency: What Is It, Causes, Symptoms, and More Osmosis 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.