Taking Ginkgo biloba every day doesn't slow cognitive decline for elderly patients, researchers found.
Older patients who took the supplement had no less a decline in memory, attention, language, or other cognitive measures than those on placebo, Dr. Steven DeKosky of the University of Virginia and colleagues reported in the Dec. 23/30 issue of the Journal of the American Medical Association.
"It's pretty safe and it's cheap, and it's not like some of the things that are either really expensive or dangerous or interfere with some other meds you might be taking," DeKosky said. "But I've got no good reason to suggest you continue to take it beyond your own blind faith."
This analysis of data from the Ginkgo Evaluation of Memory (GEM) study follows their previous analysis that found that daily use of the supplement didn't reduce the incidence of Alzheimer's disease or dementia.
"The vast majority of research shows that ginkgo is just not effective," said Dr. Lon Schneider of the University of Southern California, who wrote an editorial on the first analysis of GEMS data.
Still, ginkgo has long been marketed as a memory-enhancing supplement, with annual sales of about $250 million in the United States. It contains substances called flavonoids, which act as antioxidants and appear neuroprotective, and terpene lactones, which may reduce damage from beta-amyloid protein accumulations characteristic of Alzheimer's.
The researchers wanted to investigate whether the supplement has more subtle effects on the rate of cognitive change.
So between 2000 and 2008, they assessed 3,096 patients in the GEM study, ages 72 to 96, with a mean follow-up of about six years.
Patients took either 120 mg of Ginkgo biloba twice a day or a placebo.
The researchers found that the groups did not differ in terms of improvement of memory, attention, visuo-spatial ability, language or other brain functions. Nor did it appear that the supplement would protect from Alzheimer's disease based on the evidence from the research.
Overall, the findings suggest that Ginkgo biloba affects neither subtle preclinical cognitive changes associated with dementia nor cognitive changes associated with normal aging -- results that are consistent with smaller trials.
But the findings don't necessarily apply to acute use of the extract -- or to younger patients who are attempting to prevent disease many years in the future.
Yet DeKosky noted that "there's nothing about antioxidants that would make you think they'd help in the short-term."
"It's surely a possibility that Ginkgo biloba can be preventative, but there's an absence of evidence, no 20-year studies," Schneider said.
He cautioned that patients who choose to take Ginkgo in their 50s or later "shouldn't expect this to delay the onset of Alzheimer's."