Ginkgo Proves Effective
Against Alzheimer's Dementia

This section is compiled by Frank M. Painter, D.C.
Send all comments or additions to:    Frankp@chiro.org

Nutrition Science News

By Richard N. Podell, M.D.

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Ginkgo seems to increase blood flow to the brain, improving oxygen and glucose supplies while enhancing cognitive activity.

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There is reason for celebration among proponents of natural healing, and the guest of honor is ginkgo. Recent research results may finally convince U.S. physicians to seriously consider natural treatments. [1] It isn't because there wasn't evidence to support ginkgo as an effective treatment for dementia (declining mental power), but the evidence, until now, was not the kind U.S. physicians took seriously.

More than a dozen double-blind studies have shown that ginkgo can reduce mental decline. [2-5] Those studies did not, however, pierce the armor of our old medical paradigm--that only drugs and surgery are effective treatments for disease. Those double-blind studies were suspect in part because they were done in Europe and published in workaday journals, not the elite publications where paradigm-busters should appear.

Now, that has changed. The recent ginkgo study was done in the United States. It appeared in the Journal of the American Medical Association, a publication that ranks high in prestige and readership.

The bottom line is this: Ginkgo surpassed placebo for the treatment of Alzheimer's dementia. It is definitely not a cure, but it probably works as well as any drug that has been tried. And crucially, for this fragile group of patients, side effects were few.

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Ancient Chinese Secret:

Ginkgo biloba is the world's oldest species of tree; its ancestors date back 200 million years. Ginkgo is native to China, where it is considered a sacred tree. In traditional Chinese medicine, ginkgo is believed to benefit the brain. In Germany and France, where ginkgo is prescribed like a drug, ginkgo leaf extract accounts for more than 1 percent of drug sales. [6]

Ginkgo seems to increase blood flow to the brain, improving the supply of oxygen and glucose. At the cellular level, ginkgo stabilizes membranes, scavenges toxic free radicals, stimulates enzymes that relax arterial muscles and inhibits blood platelet clotting. [7]

For their study, researchers at the New York Institute for Medical Research in Tarrytown, N.Y., recruited more than 300 patients who had mild to moderate dementia as measured by two standard tests, the Mini-Mental State Examination and the Global Deterioration Scale. The majority of patients had Alzheimer's disease. About one-quarter had multi-infarct dementia caused by small strokes.

Three times a day patients received either a placebo or 40 mg of EGb 761, a standardized ginkgo extract that is available in Europe and the United States. Outcomes were carefully measured using three standard tests. Two measured memory, thinking skills and day-to-day function--the Alzheimer's Disease Assessment Scale (ADAS-Cog) and the Geriatric Evaluation by Relative's Rating Instrument (GERRI). One measured general psychological adjustment--the Clinical Global Impression of Change (CGIC). Patients were examined 12, 26, 39 and 52 weeks after starting the program.

For the ADAS-Cog test, the average score for the placebo group declined, whereas the ginkgo group score remained stable. The advantage of ginkgo compared to placebo was statistically significant. Of patients on ginkgo, 50 percent improved by two points or more, while only 29 percent improved on placebo.

On the GERRI test, the ginkgo group improved while the placebo group worsened. The difference favoring ginkgo was highly significant, with the probability that the result was due to chance being less than 0.004. Of patients in the ginkgo group, 37 percent improved and 19 percent became worse. The placebo group showed an opposite trend: 40 percent worsened and 23 percent improved. Thus, both tests of cognitive and social function showed improvement for patients on ginkgo compared to placebo.

On the CGIC, which measures general psychological adjustment, both groups stayed about the same. This was not surprising because the CGIC is not a sensitive measure of dementia status.

Adverse events were few. There was a small increase of incidence of gastrointestinal symptoms among patients taking ginkgo.

Overall, this was a careful, rigorous study. The authors analyzed the results to identify factors that might call the study's results into question. For example, as might be expected among patients with dementia, drop-out rates were high. Only 38 percent of the placebo patients and 50 percent of ginkgo patients completed the full year of treatment. Statistical analysis from each interval visit, however, suggests that the high drop-out rate should have made it harder to measure the positive effect of ginkgo. So the benefit of ginkgo might be even greater than it appeared.

Noncompliance, or failure to take all medicine doses, might affect results. Again, this would be expected to obscure, not enhance, the ability of ginkgo to perform better than placebo.

Subgroup analysis showed ginkgo was effective both for the entire group and for the three-fourths of patients who suffered from Alzheimer's. There were not enough patients in the multi-infarct dementia group to show a statistical benefit for ginkgo compared to placebo.

The conclusion: Ginkgo was better than placebo for treating Alzheimer's dementia. It stabilized performance during a year, and in a substantial minority of cases led to improvement. The treatment was safe; side effects were minor. We cannot yet say whether ginkgo is also effective for multi-infarct dementia.

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Industry Implications:

• Will ginkgo soon be considered conventional? It is too early to tell, but the odds look encouraging.

• Will the success of ginkgo encourage acceptance of other natural treatments? I wouldn't be surprised. Perhaps good practice will soon require that patients be informed of ginkgo as a treatment option.

• Will drug companies trump the natural products industry by identifying the active biochemicals in ginkgo, then patenting and selling them? Not for a while, but I hope they try. That kind of competition increases our knowledge and creates legitimacy that will make ginkgo better known. More likely, though, the whole herb will prove to work better than any one of its parts--after all, that is how nature evolved it to function.

Ginkgo, of course, is just one herbal medicine whose sales have expanded phenomenally in recent years. For people who want to learn more about this newly exciting field, I recommend two books. As a physician, I value Botanical Influences on Illness by Melvyn Werbach, M.D., and Michael Murray, N.D. (Third Line Press, 1994). For a skeptical but open-minded mainstream point of view, try Varro Tyler's classic book, Herbs of Choice (Pharmaceutical Products Press, 1994) or his earlier work, The Honest Herbal, 3rd Edition (Pharmaceutical Products Press, 1993).

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Richard N. Podell, M.D., is clinical professor of family medicine at the UMDNJ-Robert Wood Johnson Medical School in New Brunswick, N.J., and director of the Podell Center for Medical Treatment, Prevention and Natural Healing in New Providence, N.J.

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REFERENCES:

1. LeBars, P., et al. "A placebo-controlled, double-blind randomized trial of an extract of ginkgo biloba for dementia." JAMA, 278(16): 1327-32, Oct. 22/29,1997.

2. Kanowski, S., et al. "Proof of efficacy of the ginkgo biloba special extract EGb 761 in outpatients suffering from mild to moderate primary degenerative dementia of the Alzheimer type or multi-infarct dementia." Pharmacopsychiatry, 29: 47-56, 1996.

3. Kleijnen, J., et al. "Ginkgo biloba for cerebral insufficiency." Brit J Clin Pharma, 34: 352-58, 1992.

4. Letzel, H., et al. "Nootropics." J Drug Devel Clin Practice, 8: 77-94, 1996.

5. Hofferberth, B. "The efficacy of EGb 761 in patients with senile dementia of the Alzheimer type, a double-blind placebo-controlled study on different levels of investigation." Human Psychopharmacology, 9: 215-22, 1994.

6. Werbach, M., & Murray, M. Botanical Influences on Illness: Tarzana, Calif.: Third Line Press, 1994.

7. Ibid.

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