JAMA Study Fails To Demonstrate Ginkgo's Effect on Cognitive Function in Healthy Adults

WILLIAMSTOWN, Mass.--Ginkgo biloba does not improve cognitive function in healthy adults, according to a study published in the Aug. 21 issue of the Journal of the American Medical Association (JAMA) (288, 7:835-40, 2002) (www.jama.com). The ginkgo study was funded by the National Institute on Aging (NIA), a branch of the National Institutes of Health (NIH), and conducted by Paul R. Solomon, Ph.D., and colleagues from Williams College, based here, as well as the Southwestern Vermont Medical Center in Bennington, Mass.

To evaluate whether ginkgo could improve memory in elderly adults, researchers recruited a total of 230 healthy volunteers--98 men and 132 women--who were randomly assigned to receive either placebo or 40 mg of ginkgo (as Ginkoba®, manufactured by Locarno, Switzerland-based Boehringer Ingelheim Pharmaceuticals) three times daily, as per the labeled directions. One day prior to beginning the treatment regimen and again at the end of the six-week study, participants underwent neuropsychological testing, including verbal and nonverbal learning and memory, attention and concentration, naming and expressive language, and a self-report of memory. At the end of the study period, a family member or friend completed a questionnaire to give an impression of cognitive changes.

Of the 230 subjects who enrolled originally, 203 completed the study. Those participants who dropped out did not differ by group--11 from the ginkgo group and 16 from the placebo group dropped out for either failing to follow dosage recommendations or withdrawing consent.

Researchers stated there were no significant differences between the ginkgo and placebo groups for any of the 14 neuropsychological tests. Test results indicated half of the measures was better in the placebo group, and the other half was better in the ginkgo group. In general, participants performed better during their second evaluation than during their first, but there were no significant test-by-treatment condition interactions, according to researchers. In addition, 33 percent of the placebo group and 28 percent of ginkgo group cited minimal improvements, while three participants (two in the ginkgo group and one from the placebo group) cited much improvement.

"In summary, this study does not support the manufacturer's claims of the benefits of ginkgo on learning and memory," the authors concluded. "Treatment over a six-week period following the manufacturer's dosing suggestions did not produce objective benefit on any of 14 standard neuropsychological tests, nor were any benefits detected in self-report by the participants or observation by a family member or friend."

The natural products industry has urged reporters and consumers not to take this study as the final word on ginkgo; rather, consumers are urged to consider the entire body of evidence in support of ginkgo's beneficial use. According to the Council for Responsible Nutrition (CRN), there have been more than 120 clinical studies conducted on ginkgo to date, with the majority focusing on memory and cognition among elderly subjects with impaired cognitive function.

"This study should not be viewed as the definitive word on the subject, but simply one more addition to an extensive amount of scientific information, much of it positive, on ginkgo," said John Caredellina, Ph.D., vice president of botanical science and regulatory affairs at CRN. "This study adds to our body of knowledge, but is certainly not the final word on the subject."

The National Nutritional Foods Association (NNFA) and the American Herbal Products Association (AHPA) sent out a joint statement to clarify that numerous studies in the past have found ginkgo effective for both healthy and cognitively impaired study populations. "What's important to remember is that it's difficult to increase cognitive ability in healthy adults to a significant or even measurable degree," said Phil Harvey, Ph.D., director of science and quality assurance at NNFA. "To do so would likely require a longer trial, with doses of ginkgo titrated to a higher level over time."

Steven Dentali, Ph.D., vice president for scientific and technical affairs at AHPA, added, "Let's not forget that over a century of controlled trials on ginkgo have clearly demonstrated that those with even mild to moderate memory problems and poor concentration symptoms often associated with the onset of Alzheimer's and other dementias are helped by taking ginkgo. This study should not be the last word on ginkgo's effectiveness. Previous well-designed and -executed studies have indicated ginkgo's significant benefits in improving circulation and mental function, and should be taken seriously as a totality of scientific evidence about ginkgo."

The American Botanical Council (ABC) issued a press release of its own regarding the new JAMA study, as well. "The value of ginkgo or any dietary supplement cannot be determined on the basis of one study alone," said Mark Blumenthal, founder and executive director of ABC. "There are more than 125 clinical trials published on ginkgo extract over the past two decades, with most of them supporting numerous important benefits related to improved circulation and mental function."