Long touted as an elixir of eternal mental acuity, the herbal extract ginkgo biloba in fact does not prevent or delay the progression of dementia or Alzheimer's disease, according to a clinical trial reported today involving thousands of volunteers between the ages of 75 and 96.
The subjects swallowed round, reddish tablets twice a day for an average of more than six years, but at the end of the study, those who got ginkgo biloba were slightly more likely to be diagnosed with dementia and Alzheimer's than their counterparts who received dummy pills.
The results, published in the Journal of the American Medical Assn., are sure to disappoint the millions of people who take ginkgo in the hopes of boosting their brainpower and staving off the ravages of dementia and Alzheimer's, which affect more than 5.2 million Americans. Alzheimer's passed diabetes two years ago as the sixth-leading cause of death in the U.S., according to the Centers for Disease Control and Prevention.
"No one is more disappointed that we didn't have any traction in slowing down the disease than the group that did the study," said Dr. Steven T. DeKosky, the neurologist who led the clinical trial.
Mark Blumenthal, executive director of the American Botanical Council, a nonprofit group backed by herbal supplement makers, said the study used the right dose of the right ginkgo extract and gave the pills a reasonable amount of time to show an effect. The fact that it did not help puts ginkgo in good company, he said.
"Let's keep in mind that to date, no conventional pharmaceutical drug has shown any benefit for either preventing the onset of Alzheimer's or dementia, or even slowing it down," he said.
The National Center for Complementary and Alternative Medicine, a branch of the National Institutes of Health, began researching ginkgo in 1999 as part of a broad effort to subject unregulated herbal remedies to the same type of scrutiny that is required of medicines seeking approval from the Food and Drug Administration.
The ginkgo tree is native to China, and its extract was used in ancient times to promote general wellness, said Dr. Wallace Sampson, editor of the Scientific Review of Alternative Medicine. About 30 years ago, Europeans began testing its effects on the mental decline that often comes with aging.
Ginkgo is prescribed by physicians to preserve memory in some European countries, including Germany. In the U.S., supplement makers tout ginkgo biloba's ability to "improve mental sharpness, concentration, memory and cognitive ability," according to one purveyor.
