The widely used herbal supplement Ginkgo biloba does not appear to slow the rate of cognitive decline in healthy older people or those with mild cognitive impairment, U.S. researchers said on Tuesday.
Their study involved 3,069 people age 72 or older from four U.S. communities who were tracked for an average of six years. Half of them took twice-daily doses of 120 milligrams of extract from the leaves of the ginkgo tree and half received a placebo.
Compared with study participants who received a placebo, the use of Ginkgo biloba did not slow cognitive decline in those with normal conditions or those with mild cognitive impairment, the researchers wrote in the Journal of the American Medical Association.
The findings suggest that Ginkgo biloba - one of the top-selling herbal supplements used with the aim of improving memory and preventing age-related cognitive decline - had no effect on subtle changes associated with early symptoms of dementia or normal aging, the researchers said.
"The primary finding was no effect of the ginkgo extract over a relatively long period of time in older people in slowing down what we see as the normal changes of thinking function in aging," Dr. Steven DeKosky, dean of the University of Virginia School of Medicine and the study's leader, said in a telephone interview.
"If one thought that ginkgo might maintain cognition and prevent or delay decline in some thinking associated with aging, it did not do that," he said.
Dr. DeKosky and colleagues previously found that Ginkgo biloba was not effective in reducing the incidence of Alzheimer's dementia or dementia overall.
A supplements industry group, Council for Responsible Nutrition, said other studies suggest the herbal supplement can be effective in improving cognitive function.
"In an area where there are few other safe, affordable options, I would hate to see this study send the wrong message to consumers," Douglas MacKay, CRN vice president said in an e-mail. "I would continue to recommend Ginkgo biloba to older adults as a safe, effective option for supporting cognitive health."
The ginkgo product used in the research was made by German-based Schwabe Pharmaceuticals.