Unlike L-carnitine, acetyl-L-carnitine can pass the blood brain barrier. L-carnitine is an amino acid naturally produced by the human body, and plays a role in healthy energy production, brain and nervous system function, and healthy fat metabolism. Under conditions of stress, aging and illness, the body's ability to make L-carnitine and acetyl-L-carnitine may be reduced, making dietary sources more important.
L-carnitine is essential for the processes that allow for fatty acids to serve as one of the primary energy sources for the body. Skeletal and heart muscles obtain most of their energy from fat breakdown. For these tissues to produce energy from fat, fatty acids must be transported to specific locations (mitochondria) within cells. L-carnitine is involved in multiple steps in the transfer of individual fatty acids for energy production into the cells, allowing for a healthy breakdown of fat.