Understanding the Role of Carnitine in TPN and IDPN Therapy Ingredient Spotlight: L Carnitine Source: Biosynthesised in the body from the amino acids Lysine and Methionine, L Carnitine is a conditionally essential nutrient involved in energy metabolism and fat transport. Key Benefits The Science of Carnitine: How It Works and Why It Matters Carnitine transport and fatty acid oxidation ScienceDirect