A major cause of aging is a reduction in the energy-producing components of the cell, resulting in reduced cellular metabolic activity, and the accumulation of cellular debris.  L-carnitine helps maintain cellular energy metabolism by assisting in the transport of fat through the cell membrane and into the mitochondria within the cell, where fats are oxidized to produce the cellular energy ATP.

Acetyl-L-carnitine is the acetylated ester of the amino acid L-carnitine. Acetyl-L-carnitine is an endogenous mitochondrial membrane compound that helps maintain mitochondrial bioenergetics and lowers the increased oxidative stress associated with aging. Acetyl-L-carnitine and L-carnitine are absorbed into the bloodstream efficiently. Both are effective at carrying long-chain fatty acids across the membrane into the mitochondria where they are burned for energy production and utilized efficiently by the  cells. Acetyl-L-carnitine also guards against oxidative damage. Amyloid-beta peptide is a principal component of plaques and is thought to be a contributor to the aging process. Acetyl-L-carnitine exerts protective effects against such neurotoxicity and oxidative stress.

For some people, L-carnitine, especially acetyl-Lcarnitine, may have a stimulating effect. Therefore, it may be unwise to take it in the evening.