Carnitine: Genetic Variants Affecting Mitochondrial Energy and Health 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. L carnitine tartrate supplementation in the fight against infectious disease A Guide to L Carnitine on Keto Keto Nutrition Carnitine supplementation improves metabolic flexibility and skeletal muscle acetylcarnitine formation in volunteers with impaired glucose tolerance: A randomised controlled trial eBioMedicine The Role of l Carnitine in Mitochondria, Prevention of Metabolic Inflexibility and Disease Initiation