Applied Nutrition L Carnitine 3000mg Liquid Fruit Burst 480ml H&B New study links L carnitine in red meat to heart disease Harvard Health L Carnitine 1500 mg with Vitamin B Promote Physical Performance MaxionNutrition 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.