Called ba wei di huang wan (BDW), the herbal has been used throughout China, Japan and Korea.
After taking the supplement for eight weeks, the 16 trial subjects showed a boost in mental functioning, and in their ability to complete day-to-day activities. The placebo group saw no such benefit.
"These results argue the benefits of BDW in the treatment of dementia," write the researchers from Tohoku University School of Medicine in Miyagi, Japan, in the September issue of the Journal of the American Geriatrics Society (volume 52, issue 9, pp 1518).
The participants had mild to severe forms of dementia for an average of five years.
The reasons for this benefit are unclear, according to the researchers.