Conflicting Ginkgo Studies on Memory
August 22, 2002—A new clinical trial published in the current issue of the Journal of the American Medical Association (2002;288:835–40) suggests that Ginkgo biloba extract (GBE) does not benefit brain function in elderly persons not suffering from memory disorders. This finding runs counter to claims on ginkgo supplement labels promising improved memory or mental sharpness.
This study is one of the first to test ginkgo on elderly people not suffering from memory loss. Most ginkgo research has focused on helping older patients with Alzheimer’s disease, or related milder conditions such as age-related cognitive decline (ARCD) or cerebral insufficiency. A majority of these trials have reported positive results. Two years ago, a trial similar to the one reported this week found trends toward improvement in some measures of memory function in healthy older people given ginkgo, but the overall effect was modest at best. Studies testing ginkgo for memory enhancement in younger subjects have also reported some measurable, though mild, benefits.
In the current trial, 120 mg per day of GBE (Ginkoba®) or a placebo was given to a group of 230 healthy men and women older than 60 years who scored well on a standard assessment of mental function. These participants were evaluated with a group of neuropsychological tests before beginning supplementation and again after six weeks. The tests included evaluations of learning ability and memory, attention and concentration, and use of language. In addition, each person in the study, and someone maintaining close regular contact with the person, answered questionnaires designed to rate personal impressions of changes in the participant’s memory. The results showed no significant differences between the ginkgo and placebo groups.
The short duration and relatively low amounts of GBE used in the current study are a potential limitation, and may have contributed to the negative results. As the authors of this study acknowledge: "It is certainly possible that higher doses or longer periods of exposure than used in this study are necessary to detect changes…." Some prior successful ginkgo studies have lasted well over six weeks, and used daily amounts above 120 mg per day, although other studies have found positive results with 120 mg per day.
The cognitive and circulatory benefits of ginkgo have been well documented in over a hundred published studies. In addition to ARCD and early-stage Alzheimer’s disease, preliminary research has found ginkgo to have benefit in such varied conditions as depression (in the elderly), erectile dysfunction caused by poor circulation, macular degeneration, schizophrenia (in combination with haloperidol), vertigo, peripheral occlusive arterial disease (a condition characterized by pain in leg muscles during walking affecting many older adults), and mountain sickness (which affects hikers suffering from lack of oxygen in high altitudes). In much of this research, GBE intake was between 120 and 240 mg per day, given in divided amounts, for a duration of 8 to 12 weeks.
Ginkgo extract remains a promising treatment for age-related memory disorders. However, whether taking ginkgo has an important impact on mental function in healthy people is still an open question that will only be answered with continued research.
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James Gerber, MS, DC, is the Scientific Advisor for the Healthnotes Newsletter, an exclusive product of Healthnotes, Inc. Dr. Gerber is Associate Professor of Clinical Sciences at Western States Chiropractic College in Portland, Oregon and a member of the Adjunct Faculty of the National College of Naturopathic Medicine and the University of Bridgeport. In addition, he teaches post-graduate courses for several professional colleges. Dr. Gerber is the author of the Handbook of Preventive and Therapeutic Nutrition (Aspen, 1992) and a contributor to Conservative Management of Sports Injuries (Williams & Wilkins, 1997).
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