Nature's Truth Acetyl L Carnitine HCL 1000mg, 30 Capsules, Non GMO, Gluten Free ALCAR Supplement Walmart.com L Carnitine plays an important role in the larger metabolism equation: helping your body use fat efficiently as fuel. Learn more about the science on this week's post on The Wellness Edit. 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. Early research into L carnitine was often cited as underwhelming, showing negligible changes in muscle carnitine content and fat loss outcomes. However, these findings may have been limited by a short study window