In one study, 78 people with vascular dementia, a type of impairment from reduced blood supply to the brain, took 100 mcg of huperzine A or a placebo containing 100 mg of vitamin C twice per day. After 12 weeks, while the placebo group had not improved, the huperzine A group performed better in mental tests, had improved ratings for clinical dementia, and had better quality of daily living activities.
Huperzine A is a naturally occurring compound from the Chinese club moss, used in China as a traditional medicine.