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Ginkgo Biloba

Reprinted with permission of the National Institute on Aging, National Institutes of Health

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Ginkgo biloba has been the focus of recent media reports as a potential treatment for Alzheimer's disease. The National Institute on Aging reports that a 1997 ginkgo biloba study suggests that a ginkgo biloba extract may be of some help in treating the symptoms of Alzheimer's disease and vascular dementia (stroke). The study provides no evidence that ginkgo biloba will cure or prevent Alzheimer's disease, but says that ginkgo biloba treats the symptoms.

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Benefits of Ginkgo Biloba

• Ginkgo biloba enhances microcirculation.
• Ginkgo biloba improves blood flow and oxygen supply to the brain, eyes, ears, and limbs.
• Ginkgo biloba protects cells from free radical damage.
• Ginkgo biloba inhibits platelet activating factor.

Uses Outside the United States
For centuries, extracts from the leaves of the ginkgo biloba tree have been used as Chinese herbal medicine to treat a variety of medical conditions. In Europe and some Asian countries, standardized extracts from ginkgo biloba leaves are taken to treat a wide range of symptoms, including dizziness, memory impairment, inflammation, and reduced blood flow to the brain and other areas of impaired circulation. Because ginkgo biloba is an anti-oxidant, some claims have been made that it can be used to prevent damage caused by free radicals (harmful oxygen molecules). Germany recently approved ginkgo biloba extracts (240 mg a day) to treat Alzheimer's disease.

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Ginkgo Biloba for Dementia from Alzheimer's Disease and Stroke
Researchers at the New York Institute for Medical Research in Tarrytown, New York, conducted a major clinical study of ginkgo biloba and dementia. Their findings were published in the Journal of the American Medical Association (October, 1997). These scientists examined how taking 120 mg a day of a ginkgo biloba extract affected the rate of cognitive decline in people with mild to moderately severe dementia due to Alzheimer's disease and stroke. They reported that an extract of Ginkgo biloba can stabilize and, in some cases, improve the cognitive function and the social behavior of demented patients for six months to one year.¹ What if they had used the Germany approved 240 mg a day dosage listed above?

The research was a one-year, double blind, placebo-controlled, parallel-group, multicenter study. The authors conclude: "EGb (from ginkgo biloba) appears to stabilize and, in an additional 20 percent of cases (vs. placebo), improve the patient's functioning for periods of six months to one year. Regarding its safety, adverse events associated with EGb (ginkgo biloba) were no different from those associated with placebo." The researchers found that 27 percent of patients treated 26 weeks or more with ginkgo biloba achieved at least a four point improvement on the 70 point Alzheimer Disease Assessment Scale-Cognitive subscale (ADAS-Cog), compared with 14 percent taking placebo; on the Geriatric Evaluation by Relative's Rating Instrument (GERRI), the daily living and the social behavior of 37 percent were considered improved with ginkgo biloba, compared to 23 percent taking placebo. The authors write: "On the ADAS-Cog, 50 percent of the EGb (ginkgo biloba) patients showed an improvement by at least two points compared with 29 percent of the placebo group; this approximately two-fold difference was still observed when the threshold to detect an improvement in cognition was set at four ADAS-Cog points. On GERRI, 37 percent of the ginkgo biloba group was considered improved while only 19 percent were considered worse; the placebo group demonstrated the opposite trend with 40 percent worsening and 23 percent improving."¹

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Ginkgo Biloba's Effect on Short-term Memory and Concentration
In at least 10 controlled clinical studies in elderly people with declining brain function due to cerebral insufficiency, those taking ginkgo biloba experienced significant improvements in mental performance, including short-term memory and concentration. Researchers also noted benefits to mood, attention, and sociability.

Limited, but promising research suggests that ginkgo biloba may also help maintain and improve brain function in young, healthy people. In several small studies in healthy people, short-term memory, attention, and response time were significantly improved after single doses of ginkgo biloba extract.^2,3

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Ginkgo Biloba in Other Studies
Hundreds of published laboratory studies document the complex and varied effects of ginkgo biloba, and at least 44 double blind clinical studies involving 9,772 people have investigated the effects of ginkgo in a variety of different health conditions.

A number of clinical studies have demonstrated the effectiveness of ginkgo biloba extract in the treatment of peripheral artery disease, a narrowing of the arteries in the legs that causes painful cramping. In these trials, there was a significant increase in pain-free walking distance after treatment with ginkgo biloba extract.⁴

An interesting study evaluated the effects of ginkgo biloba extract on altitude sickness. In this study, ginkgo biloba was significantly more effective than placebo in improving tolerance to high altitude and preventing typical symptoms of altitude sickness.⁵

Currently researchers are evaluating the effects of ginkgo biloba extract in the treatment of hearing loss, cataracts, asthma, depression (in people unresponsive to drug treatment), and a variety of other conditions.

The National Institute on Aging (NIA) and the Office of Alternative Medicine, both at the National Institutes of Health, are funding a small study to test the effectiveness of ginkgo biloba in treating Alzheimer's disease. This 2-year study at the Oregon Health Sciences University in Portland started in 1997. It will include 42 patients with mild to moderate Alzheimer's disease. (2001 - NIA has not published the results yet.)

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Safety and Side Effects
People should consult with their family doctors before using ginkgo biloba extracts. This is especially true for those with disorders in blood circulation or blood clotting and those taking anti-coagulants such as aspirin. Many different preparations of ginkgo biloba extract are available over the counter. They vary in content and active ingredients. No specific daily amount of a ginkgo biloba extract can be recommended (at this time by the National Institutes of Health) as safe or effective.

Anyone who is worried about a memory problem should see a doctor. Symptoms similar to those caused by Alzheimer's disease may be caused by other medical conditions, including a high fever, dehydration, vitamin deficiency and poor nutrition, bad reactions to medicines, thyroid problems, depression, or a minor head injury. Medical problems like these are serious and should be treated by a doctor as soon as possible.

In addition, some recent case studies imply that daily use of ginkgo biloba extracts may cause side effects, such as mild gastrointestinal discomfort, headache, and rash.⁶ No contraindications are known, although caution is advised for people with blood clotting disorders, or those regularly taking aspirin. Some experts advise that ginkgo should not be taken by those who are taking prescription antidepressant drugs known as monoamine oxidase inhibitors (MAOI), because there is a theoretical possibility that the combination could result in a negative drug interaction.⁷

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References

1. LeBars PL, Katz MM, Berman N, et al. A placebo-controlled, double-blind, randomized trial of an extract of Ginkgo biloba for dementia. JAMA. 1997; 278: 1327-1332.
2. Hindmarch I. Activity of ginkgo biloba extract on short-term memory. In: Fungeld EW, ed. Rokan (ginkgo biloba). Recent Results in Pharmacology and Clinic. Berlin, Heidelberg, and New York: Springer Verlag, 1988; 321-326.
3. Allard M. Effects of ginkgo biloba extract on normal or altered memory function in man. In: Christey Y, Costentin J, Lacour M, eds. Effects of Ginkgo biloba extract on the central nervous system. Paris: Elsevier, 1992.
4. Peters H, Kieser M, Holscher U. Demonstration of the efficacy of ginkgo biloba special extract EGb 761 on intermittent claudication - a placebo-controlled, double-blind multicenter trial. Vasa 1998; 27: 106-110.
5. Roncin JP, Schwartz F, D'Arbigny P. Egb 761 in control of acute mountain sickness and vascular reactivity to cold exposure. Aviation, Space and Environmental Medicine 1996; 67 (5): 445-452.
6. Blumenthal M, Busse W, Goldberg A, et al., eds. The Complete German Commission E Monographs. Austin, TX: The American Botanical Council; Boston: Integrative Medical Communications, 1998.
7. McGuffin M, Hobbs C, Upton R, et al., American Herbal Products Association Botanical Safety Handbook. Boca Raton, FL; CRC Press, 1997.

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Non-referenced sections reprinted with permission of:
U.S. Department of Health and Human Services
Public Health Service
National Institutes of Health
National Institute on Aging
Published in May 1998

Photo courtesy of NIEHS News: Environmental Health Perspectives Volume 107, Number 12, December 1999