A six-year clinical study showed that the eighth most popular herb and a hot-selling herbal supplement ginkgo biloba do no wonder to mental decline.

The herb has been believed to be an aid to improving memory, cognitive impairment, dementia and Alzheimer's disease since 1970s. It is an extract derived from the ginkgo tree. American Botanical Council states that the extract has been used in traditional Chinese medicine for more than 500 years.

Study leader Steven T. DeKosky, MD, and colleagues tried to find out for some sign that ginkgo might slow mental decline in healthy, aging individuals but no such sign was found.

Extract from Schwabe Pharmaceuticals that is sold as a medication in Germany was used for the study.

The tests showed that gingko doesn't help slow cognitive decline in the 72- to 96-year-old study participants.

The Council for Responsible Nutrition, a group representing the supplement industry, however stated that the DeKosky study should not be referred to as a final study.

U. S. sales for ginkgo biloba were $99 million in 2008, down 8% from 2007.