Ginkgo biloba—a staple in traditional Chinese medicine for 500 years—has been subjected to a range of clinical trials over the last 30 years, regarding its ability to improve peripheral circulation and cognitive function in patients with early stages of mild cognitive impairment, senile dementia, Alzheimer’s disease and memory loss. A recently published study in the Journal of the American Medical Association, however, has seemingly upended the annals of research on the extract, refuting its ability to slow cognitive decline.

In the “Ginkgo biloba for Preventing Cognitive Decline in Older Adults A Randomized Trial” (JAMA, 2009; 302(24):2663-2670), researchers reexamined data from an earlier trial published in JAMA in November 2008. The earlier Ginkgo Evaluation of Memory (GEM) study dosed 3069 participants aged 72 to 96 years with 120 mg extract of G. biloba (or a placebo) twice a day to determine whether the extract slowed the rates of global or domain-specific cognitive decline in older adults. The research was conducted across six U.S. academic medical centers in the U.S. between 2000 and 2008, and had a median follow-up of 6.1 years.

At the conclusion of the GEM study, researchers found that the annual rates of decline did not differ between patients taking ginkgo and the placebo in any of the monitored domains, which included memory, attention, visuospatial abilities and executive functions.

“The new publication by Snitz et al. is not a new trial, despite the way it has been misreported by mainstream electronic media in newspapers and other reports,” said the American Botanical Council (ABC) in a press release. “In that earlier trial, a leading ginkgo extract did not prevent the onset of cognitive decline or Alzheimer’s disease. That earlier presentation was not designed to determine cognitive decline, the subject of the new publication.”

“The results of this new trial must be viewed in proper perspective,” noted Mark Blumenthal, founder and executive director of the American Botanical Council (ABC). “There is a vast body of pharmacological and clinical research supporting numerous health benefits for ginkgo extracts, particularly for improving various symptoms and conditions associated with declining cognitive performance and poor circulation.”

In addition to skewed perspective, Mr. Blumenthal pointed out that in the original study, about 40% of the subjects dropped out over the six-year duration of the trial and that the subjects in the study were not monitored for certain cognitive parameters until several years after the trial began, creating difficulty in determining accurately whether they experienced a decline in cognition or not.

What’s also worth noting, he said, was the advanced age of the study participants (an average of 79 years at the beginning of the trial). “This age group is not typical of the age of both healthy people and those with mild cognitive impairment who use ginkgo for improving mental performance,” he said.

Further, ABC noted that another weakness of this trial is the lack of an active control (i.e., a potential third arm of the trial, besides the patients on ginkgo or placebo) in which patients would have used a pharmaceutical medication with presumed efficacy, to determine to what extent the particular population being tested would respond. “This was not possible for this trial since no conventional pharmaceutical drug has ever demonstrated the ability to prevent the onset of dementia or diminish its progression,” said ABC.

“This trial is not conclusive nor should it in any way detract from ginkgo’s reputation as a useful dietary supplement to help support and improve cognitive function and enhance peripheral circulation—conditions for which it has been reported to be effective in numerous clinical trials,” reminded Mr. Blumenthal.

He went on to add that at least 16 controlled clinical trials have evaluated various ginkgo extracts for healthy, non-cognitively impaired adults. A systematic review demonstrated that in 11 of these trials, ginkgo increased short-term memory, concentration and time to process mental tasks.

The Council for Responsible Nutrition (CRN) issued a similar statement. “It is important to put this study into context and to remember that there is a large body of previously published evidence, which suggests that Ginkgo biloba may help improve cognitive impairment in older adults,” remarked Douglas MacKay, ND, vice president, scientific and regulatory affairs, CRN.

There are also additional ongoing clinical trials, he added, the results of which may address some of the limitations of the current study. The results of this single study add to the overall data on Ginkgo biloba, including valuable evidence in support of Ginkgo’s safety profile, but should not be viewed as the final word. In addition, several studies have demonstrated that Ginkgo biloba can be used to improve blood circulation and reduce oxidative stress, two risk factors associated with the progression of cognitive decline, dementia and Alzheimer’s disease.

Dr. MacKay added that it’s important to remember that cognitive decline, dementia and Alzheimer’s disease are multi-factorial chronic conditions that might require a multi-component, integrative approach.

“As a former practicing licensed naturopathic doctor, I have had the benefit of working with patients and have seen first-hand how Ginkgo biloba 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,” he said. “I would continue to recommend Ginkgo biloba to older adults as a safe, effective option for supporting cognitive health and would encourage consumers to talk to their own healthcare professional about what is right for them.”