The study was designed and conducted by the paper's lead author, Paul R. Solomon, Ph.D., professor of psychology and founding chair of the college's Neuroscience Program, Richard D. De Veaux, Ph.D., professor of statistics, and three students: Felicity Adams, Amanda Silver, and Jill Zimmer.
Extract from leaves of the tree ginkgo biloba is marketed worldwide as an enhancer of memory and other mental functions. In 1998, $310 million dollars worth was sold in the U.S. alone.
Researchers identified 230 volunteers over the age of 60 who were physically and mentally healthy. They gave them 14 tests of learning, memory, and attention and concentration, and had them and their companions (e.g. spouses, partners, close friends) rate the participants' mental functions on subjective scales.
Participants were then randomly divided into two groups: one to take gingko and one placebo. The study was double-blind; neither the participants nor the researchers knew who was taking ginkgo and who was taking placebo.
The manufacturer claims beneficial effects can be noticed after four weeks. After six weeks, participants in the study retook the 14 standardized tests and they and their companions re-rated participants' mental functions. There were no significant differences between those taking ginkgo and those taking placebo on any of the objective or subjective measures.
"Many of our patients and their families who are seen at the Memory Clinic in Bennington have asked whether ginkgo could slow or reverse the effects of aging on memory," Solomon said. "Since there were no scientifically rigorous studies of this, we decided to conduct a study of ginkgo on memory. The results indicate that when taken following the manufacturer's instructions, ginkgo provides no measurable benefit in memory, attention, or concentration in healthy older adults. We hope others will now further test ginkgo and other vitamins and nutrients to see if they really provide the benefits they claim.
"As with any over-the-counter substance, people taking ginkgo, or thinking of taking it, have to decide for themselves what's right but they owe it to themselves to inform that decision with knowledge of scientific studies. They also need to consider cost and possible side effects, especially if taken with medication or other substances."
Other researchers welcomed the study. "It is critically important that claims of effectiveness of all treatments, including natural products, be supported by scientifically valid results from well controlled clinical trials," said Steven H. Ferris, Ph.D., Friedman Professor for Alzheimer's Disease at NYU School of Medicine and executive director of the Silberstein Institute for Aging and Dementia. "This important, very well conducted clinical trial clearly calls into question previously unsubstantiated claims that ginkgo biloba improves mental function in older people."
The study was supported by grants from the National Institute on Aging, the Howard Hughes Medical Institute, and the Essel Foundation.
Editors: Paul Solomon will be available for individual interviews Aug. 20 from 9 a.m. to 3 p.m. in New York City at The Williams Club (24 East 39th Street). To schedule an interview, on the 20th or any day, contact Cynthia Murphy, Executive Director of the Memory Clinic (cell phone: 413-281-0576).