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Ginkgo

Other common name(s): ginkgo biloba, maidenhair tree, EGb 761

Scientific/medical name(s): Ginkgo biloba

Description

Ginkgo is an extract of leaves from a ginkgo tree, one of the world's oldest surviving species of tree, which comes from China, Japan, and Korea. Ginkgo is used as a dietary supplement in the United States for a variety of conditions.

Overview

Ginkgo has shown some benefit in the treatment of mild to moderate dementia. Other studies have shown that it can help improve blood circulation and flow to the brain. Few side effects have been reported, but it has the potential to interfere with blood clotting, anesthesia, and some medications. Available scientific evidence does not support claims that it is effective in preventing or treating cancer in humans.

How is it promoted for use?

Ginkgo is promoted as an aid to memory and concentration. It is believed to stimulate blood circulation and the flow of oxygen to the brain. Widely used in Europe, the extract has also become popular in the United States. Claims include improved memory and vision in the elderly and a slowing of the progression of Alzheimer's disease and dementia.

Ginkgo is sometimes promoted for tinnitus (ringing in the ears), sudden deafness, dizziness, altitude sickness, and intermittent claudication (cramp-like pain in the lower legs caused by poor circulation). In addition, ginkgo has been used as a treatment for a blood vessel disorder known as Raynaud's disease, in which the toes or fingers turn cool and pale when exposed to cold because of insufficient blood supply. European and Asian doctors have also used ginkgo in stroke patients to attempt to limit tissue damage to the brain.

Although ginkgo is not usually promoted as a cancer treatment, herbalists note that it contains some substances that may prove to have activity against cancer, including flavonoids, which are thought to be anti-inflammatory, and proanthocyanidins, which are antioxidants. It also contains a compound called ginkgolide B, which may counteract a body chemical called platelet-activating factor (PAF) that is thought to promote tumor growth.

What does it involve?

Ginkgo leaf extract is on the Commission E (Germany's regulatory agency for herbs) list of approved herbs and can be taken by mouth in pill or liquid form. The average dose of ginkgo extract is 120 to 240 milligrams per day, usually divided into 2 to 3 doses. Proponents usually do not recommend the crude, dried leaf preparations because they claim this preparation does not contain enough of the active ingredients.

What is the history behind it?

Chinese herbalists have used the fruit of the ginkgo tree for about 4,000 years as a remedy for asthma, coughs, and allergic reactions. Cooked ginkgo seeds are also sometimes eaten after the pulp has been removed from the outside. In the past few decades, an extract of ginkgo leaves has been used in Western medicine, first in Europe and more recently in the United States, because it is supposed to help memory, brain function, and blood circulation.

What is the evidence?

The possible effects of ginkgo leaf extract in preventing or treating cancer have not been well studied. Some small studies done in Asia have suggested that ginkgo extract may affect cancer cells in culture dishes and laboratory animals, but no studies have been done to show it can prevent or treat cancer in humans. A few small studies have looked at adding ginkgo to other treatments in cancer patients, but the results have not been conclusive. More research is needed in this area.

Ginkgo leaf extract appears to improve blood flow to the brain. Some, but not all, studies have found positive results from ginkgo extract on memory. Most randomized, controlled studies have found that ginkgo extract can improve cognitive and social function in patients with mild to moderate dementia resulting from Alzheimer’s disease or problems with blood circulation in the brain. Results of its effects on memory and concentration in people without dementia have been mixed.

Some studies have found ginkgo leaf extract may have modest benefits in patients with claudication or sudden hearing loss. A 2004 review of studies concluded that there was not enough evidence to support claims that ginkgo can help tinnitus.

Are there any possible problems or complications?

This product is sold as a dietary supplement in the United States. Unlike companies that produce drugs (which must provide the FDA with results of detailed testing showing their product is safe and effective before the drug is approved for sale), the companies that make supplements do not have to show evidence of safety or health benefits to the FDA before selling their products. Supplement products without any reliable scientific evidence of health benefits may still be sold as long as the companies selling them do not claim the supplements can prevent, treat, or cure any specific disease. Some such products may not contain the amount of the herb or substance that is written on the label, and some may include other substances (contaminants). Though the FDA has written new rules to improve the quality of manufacturing processes for dietary supplements and the accurate listing of supplement ingredients, these rules do not take full effect until 2010. And, the new rules do not address the safety of supplement ingredients or their effects on health when proper manufacturing techniques are used.

Most such supplements have not been tested to find out if they interact with medicines, foods, or other herbs and supplements. Even though some reports of interactions and harmful effects may be published, full studies of interactions and effects are not often available. Because of these limitations, any information on ill effects and interactions below should be considered incomplete.

Ginkgo leaf extract is generally considered safe. Some possible side effects include headache, mild stomach upset, and diarrhea. Because of its potential to block platelet-activating factor, ginkgo is not recommended for people using aspirin, other non-steroidal anti-inflammatory drugs (such as ibuprofen), or blood-thinning medications such as warfarin (Coumadin). Doctors often advise stopping the use of ginkgo extract several days before surgery. People with seizure disorders should not use ginkgo because it may reduce the effects of seizure medication. Potential interactions between ginkgo and other drugs and herbs should be considered. Some combinations may be dangerous. Always tell your doctor and pharmacist about any herbs you are taking.

Allergic reactions to gingko have been reported, including severe skin reactions with blistering. People who react to poison ivy, mango, cashews, and sumac may be more likely to react to ginkgo.

Uncooked ginkgo fruit or seed can cause more serious problems, including vomiting, seizures, and loss of consciousness. The seed contains a toxin that is reportedly inactivated by cooking. Poisoning from eating the seeds has been reported in adults and children, sometimes resulting in death. The uncooked fruit and seed are also more likely to cause allergic rashes and intestinal irritation than the leaf extract.

This herb has not been studied in women who are pregnant or breast-feeding. Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.

Additional Resources

More information from your American Cancer Society

The following information on complementary and alternative therapies may also be helpful to you. These materials may be found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-ACS-2345).

References

Birks J, Grimley EV, Van Dongen M. Ginkgo biloba for cognitive impairment and dementia. Cochrane Database Syst Rev. 2002;(4):CD003120.

Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Austin, TX: American Botanical Council; 1998.

Ginkgo. Memorial Sloan-Kettering Cancer Center Web site. http://www.mskcc.org/mskcc/html/69235.cfm. Updated February 29, 2008. Accessed June 4, 2008.

Gruenwald J. PDR for Herbal Medicines. 3rd ed. Montvale, NJ: Thomson PDR; 2004.

Hasegawa S, Oda Y, Ichiyama T, Hori Y, Furukawa S. Ginkgo nut intoxication in a 2-year-old male. Pediatr Neurol. 2006;35:275-276.

Hilton M, Stuart E. Ginkgo biloba for tinnitus. Cochrane Database Syst Rev. 2004;(2):CD003852.

Le Bars PL, Katz MM, Berman N, Itil TM, Freedman AM, Schatzberg AF. A placebo-controlled, double-blind, randomized trial of an extract of Ginkgo biloba for dementia. North American Egb Study Group. JAMA. 1997;278:1327-1332.

Miwa H, Iijima M, Tanaka S, Mizuno Y. Generalized convulsions after consuming a large amount of gingko nuts. Epilepsia. 2001;42:280-281.

National Center for Complementary and Alternative Medicine, National Institutes of Health. Ginkgo. National Center for Complementary and Alternative Medicine Web site. http://nccam.nih.gov/health/ginkgo/. Updated May 27, 2008. Accessed April, 18, 2007.

Natural Standard. Herbal/plant therapies: ginkgo (ginkgo biloba l.). Complementary/Integrative Medicine Education Resources, The University of Texas M.D. Anderson Cancer Center Web site. http://www.mdanderson.org/departments/cimer/display.cfm?id=6bf16f2a-7c12-4546-8b39271278bdf215&method=displayfull. Accessed June 4, 2008.

Sierpina VS, Wollschlaeger B, Blumenthal M. Ginkgo biloba. Am Fam Physician. 2003;68:923-926.

Suzuki R, Kohno H, Sugie S, Sasaki K, Yoshimura T, Wada K, Tanaka T. Preventive effects of extract of leaves of ginkgo (Ginkgo biloba) and its component bilobalide on azoxymethane-induced colonic aberrant crypt foci in rats. Cancer Lett. 2004;210:159-169.

Ye B, Aponte M, Dai Y, Li L, Ho MC, Vitonis A, Edwards D, Huang TN, Cramer DW. Ginkgo biloba and ovarian cancer prevention: Epidemiological and biological evidence. Cancer Lett. 2007;251:43-52. Epub 2006 Dec 27.

Zeng X, Liu M, Yang Y, Li Y, Asplund K. Ginkgo biloba for acute ischaemic stroke. Cochrane Database Syst Rev. 2005;(4):CD003691.

Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.

Last Medical Review: 11/01/2008
Last Revised: 11/01/2008

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