The popular herbal supplement ginkgo biloba does not prevent or slow the progression of Alzheimer’s in any way, researchers said.

Lead author Dr. Steven DeKosky, vice president and dean at the University of Virginia School of Medicine, examined about 3,000 people age 75 and more. None of the participants had Alzheimer's disease when the study began. Approximately 50 percent of them were administered 240 milligrams a day of the Ginkgo biloba special extract EGb 761, an anti-dementia drug that enhances cognitive functioning and stabilizes mood in cognitively impaired seniors. The other half was given placebos.

During the 6-year follow-up, researchers found that 18 percent of people who took ginkgo biloba were diagnosed with dementia, in contrast with 16 percent of those who took placebo. While those assigned to the first group also included 257 cases of Alzheimer’s, in the second one there were reported 220 cases of the severe disease. Therefore, the team of researchers concluded that the herb ginkgo isn’t able to prevent or delay the progression of dementia.

"I'm disappointed," said DeKosky, who was chair of the department of neurology at the University of Pittsburgh, PA, at the time of the study. "It would've been wonderful to find something relatively well known and inexpensive that might have been helpful and protective."

The findings, which appeared in the Nov. 19 issue of The Journal of the American Medical Association, will definitely let down millions of seniors who take ginkgo biloba, hoping that it will prevent or slow the progress of dementia, the gradual decline in cognitive function.