Acetyl-L-carnitine is a form of carnitine, a substance used in production of energy in cells. It is manufactured by the body, and also found in meat, fish, poultry and milk. Studies of carnitine for memory loss have had mixed results. University of California researchers conducting a clinical trial of carnitine for Alzheimer’s found the supplement did not slow the progression of the disease in people over 65 or in people 65 and under. However, a review of multiple studies of carnitine for Mild Cognitive Impairment and mild Alzheimer’s disease did show a beneficial effect.