Neither group suffered serious side effects.
"We did show it was fairly safe -- that is of some reassurance," said DeKosky, dean of the University of Virginia Medical School. The only harm that could come from taking ginkgo, he said, is "spending money on something that may not be useful."
Ginkgo might still be effective if people start taking it in their 40s or 50s, when Alzheimer's begins to take root in the brain. But tracking thousands of people over several decades isn't realistic for a clinical study, said DeKosky, who has received financial support from pharmaceutical companies.
French researchers are currently testing the same ginkgo extract in 2,854 people older than 70 who are already suffering from memory problems. The results of that clinical trial will be available in 2010.
"That may show an effect that was missed in this study," said Maria C. Carrillo, a neuroscientist and director of medical and scientific relations for the Alzheimer Assn. in Chicago.
But Dr. Lon S. Schneider, a geriatric psychiatrist who studies Alzheimer's at USC who wrote an editorial accompanying the study, said it's time to give up on the herb.
"The basic science is still good, that antioxidants protect neurons," said Schneider, who has received financial support from Schwabe Pharmaceuticals as well as companies developing Alzheimer's drugs. "We can make it work in animals, but we can't seem to make this work in humans."
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karen.kaplan@latimes.com
