What is Doctor's Best Acetyl L-Carnitine? Doctor's Best Acetyl-L-Carnitine is a naturally occurring form of L-Carnitine which is a vitamin-like nutrient synthesized in the body from the amino acids lysine and methionine. It supports cognitive function and supports healthy brain neuron function. Acetyl-L-Carnitine plays a key role in the production of acetylcholine, an important neurotransmitter for brain and nerve cell function. Acetyl-L-Carnitine helps supply the brain with energy by increasing mitochondrial efficiency, supports nerve growth factor production and helps to uphold the integrity of intracellular membranes. Doctor's Best Acetyl-L-Carnitine contains Biosint Acetyl-L-Carnitine, which is manufactured in Italy by the reputable company Sigma-Tau with a patented, FDA-approved process that fully complies with the USP 25, FCC 4 and EU monographs. How does it work? Acetyl-L-Carnitine serves as a transport molecule for "active acetate," which is a source of fuel for metabolic processes that take place in cells. Acetyl-L-Carnitine carries active acetate (the "Acetyl" portion) directly into the mitochondrion, the cell's energy-generating structure. Active acetate is used to produce cellular energy in the form of ATP. Unlike L-carnitine, Acetyl-L-Carnitine readily crosses the blood-brain barrier, where it has specific benefits for brain neurons.