If you are like a lot of people, you may have never heard of carnitine but this important nutrient is critical for our body's ability to optimally burn fat required for energy. The leading ingredient in any energy drink is usually caffeine. Most of them contain herbs, caffeine, and other substances. Many energy drink brands claim to be supplements. The FDA doesn't approve energy L Carnitine and Sleep: Does It Affect Rest or Sleep Quality? L Carnitine: Benefits, Risks, and Its Role in Fitness and Weight Loss WellnessPulse L Theanine Benefits, Uses, Side Effects, Dosage, Foods Dr. Axe A carnitine transporter at the bloodbrain barrier modulates sleep via glial lipid metabolism in Drosophila PNAS