Does acetyl-l-carnitine prevents alzheimer's disease and dementia?

No: There is no definitie evidence that anything can prevent alzheimers disease. There is suggestive evidence that exercise and treating high blood pressure and diabetes can decrease the risk of it.

Alternatives: Although much is hyped in the alternative supplement market, most of the products are worthless. Theoretically, medical foods, such as cerefolin-nac might offer some potential, research has failed to show substantial benefit so far. Talk with your doctor prior to purchasing supplements.