New JAMA Study: Ginkgo Doesn't Improve Memory

By Melissa Lee Phillips
Neuroscience for Kids Consultant
September 25, 2002

The sale of herbal supplements has become a multimillion dollar industry. Companies now sell many different herbal extracts, claiming that they can help with a variety of problems such as low energy, memory loss, and obesity. Unfortunately, few of these claims have been substantiated by scientific studies exploring the effectiveness of these supplements. One particularly popular herbal supplement is ginkgo. Ginkgo is extracted from the leaves of the ginkgo biloba tree. Manufacturers of this supplement claim that ginkgo can improve memory abilities in normal, healthy subjects in as few as four weeks. Results from a study published in the August 21, 2002 issue of Journal of the American Medical Association (JAMA) suggest otherwise.

Paul Solomon, Ph.D., and his colleagues at Williams College studied the effects of a commonly available ginkgo supplement in 203 healthy subjects over the age of 60 years. None of the subjects had any previous memory problems. Before the study began, all participants completed 14 standard tests that measured their memory, concentration, attention, and learning abilities. They also filled out questionnaires that asked them to evaluate their own memory skills. For the next six weeks, half of the subjects took ginkgo according to the manufacturer's instructions: 120 mg per day (40 mg, 3 times a day). The other half of the participants took a placebo pill, made only of sugar. The study was double-blind; in other words, neither the study's subjects nor the researchers evaluating the data knew which participants took ginkgo and which took the placebo. After six weeks of taking ginkgo (or the placebo), the subjects repeated all 14 psychological tests and the questionnaire. Additionally, a companion of each participant -- perhaps a spouse, family member, or close friend -- was asked to complete a questionnaire, evaluating the subject's memory changes over those six weeks based on their own observations.

The researchers found no differences between the memory abilities of people in the ginkgo group and those in the placebo group. Both groups performed slightly better in the memory tests the second time. This observation may be the result of practice: subjects were better the second time simply because they had taken the tests before. There were also no differences between the self-questionnaire results of the two groups. Those subjects taking gingko were no more likely to think that their own memory abilities had improved over the six weeks. Similarly, the companions of people in the ginkgo group reported no more noticeable memory changes than the companions of people in the placebo group.

The researchers acknowledge that their study is not conclusive. It is possible that the study's participants did not take the supplement for a long enough time period or perhaps the subjects did not take a high enough dosage. The study also did not address the possibility that ginkgo might be effective for people with memory problems such as Alzheimer's disease or other forms of dementia. Indeed, there is some experimental evidence to suggest a possible benefit of ginkgo for Alzheimer's patients. Nevertheless, according to the manufacturer's claims, a normal, healthy person should have noticed improvements in memory in just four weeks with this dosage. But according to the new JAMA study, for those people simply wishing for better memory...forget ginkgo.

Did you know?

The word "placebo" comes from the Latin phrase that means "I will please."

Hear IT!: "Placebo"

For references and more information, see:

  1. Solomon, P.R., Adams, F., Silver, A., Zimmer, J., and DeVeaux, R. "Ginkgo for memory enhancement: a randomized controlled trial." JAMA, 288:835-840, 2002.
  2. Le Bars, P.L., Katz, M.M., Berman, N., Itil, T.M., Freedman, A.M., and Schatzberg, A.F. "A placebo-controlled, double-blind, randomized trail of an extract of Ginkgo biloba for dementia. North American EGb Study Group." JAMA, 278: 1327-1332, 1997.
  3. Memory Games - from Neuroscience for Kids
  4. Smart Drugs - from Neuroscience for Kids

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