LCarnitine pure LCarnitine supplement supports fat metabolism MuscleTrail Fat Burner L Carnitine Linus Pauling Institute Oregon State University The Role of l Carnitine in Mitochondria, Prevention of Metabolic Inflexibility and Disease Initiation What is L carnitine? Reducing fatigue Life Extension Europe 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.