L Carnitine: Benefits, Side Effects, And Dosage, Per Dietitians Did you know L carnitine, a vital amino acid, is naturally produced by your body and found in various foods? While acetyl L carnitine (ALCAR) can be a beneficial supplement for some, most people get L Carnitine 250 mg: Boost Energy & Enhance Metabolism Mountainside Medical 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