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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. It 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 (decline in mental ability). Other studies have shown that it can help improve blood circulation and flow to the brain. Few side effects have been reported with its use, 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. Ginkgo is believed to stimulate blood circulation and the flow of oxygen to the brain. Widely used in Europe, the extract has since 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 or dementia.

Ginkgo is sometimes promoted for tinnitus (ringing in the ears), sudden deafness, dizziness, altitude sickness, and intermittent claudication (a cramp-like pain in the lower legs due to poor circulation). In addition, it 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 an insufficient blood supply. European and Asian doctors have also used ginkgo in stroke patients to see if it would limit tissue damage to the brain.

Although not usually promoted as a cancer treatment, herbalists note that ginkgo 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 that may counteract a body chemical called platelet-activating factor (PAF), which 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 in pill or liquid form by mouth. The average dose of ginkgo extract is 120 to 240 milligrams (mg) per day, usually divided into 2 to 3 doses. Proponents usually do not recommend the crude, dried leaf preparations because they claim they do not contain enough of the active ingredients. 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 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?

Memory and Concentration

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.

Other Conditions

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

Cancer

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 be active against cancer cells in culture dishes and lab 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.

Are there any possible problems or complications?

This product is sold as a dietary supplement in the United States. Unlike drugs (which must be tested before being allowed to be sold), the companies that make supplements are not required to prove to the Food and Drug Administration that their supplements are safe or effective, as long as they don't 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). Actual amounts per dose may vary between brands or even between different batches of the same brand.

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" drugs such as warfarin (Coumadin). Doctors often advise stopping its use several days before surgery. People with seizure disorders are advised to avoid using 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 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 which is reportedly inactivated by cooking. Poisoning from eating the seeds has been reported in adults and children, sometimes resulting in death. The fruit/seed is 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, 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 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.

Gruenwald J, Brendler T, Jaenicke C, eds. PDR for Herbal Medicines, Third Edition. Thomson PDR, Montvale NJ, 2004.

Hasegawa S, Oda Y, Ichiyama T, et al. 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, et al. 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.

Memorial Sloan-Kettering Cancer Center. About herbs: Ginkgo. 2006. Available at: http://www.mskcc.org/mskcc/html/69235.cfm. Accessed April 18, 2007.

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

MD Anderson Cancer Center. Patient Monograph: Ginkgo. 2004. Available at: www.mdanderson.org/departments/cimer/display.cfm?id=6bf16f2a-7c12-4546-8b39271278bdf215&method=displayfull&pn=6eb86a59-ebd9-11d4-810100508b603a14. Accessed April 18, 2007.

NCCAM, National Institutes of Health. Ginkgo. Available at: http://nccam.nih.gov/health/ginkgo/. Accessed April 19, 2007.

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

Suzuki R, Kohno H, Sugie S, et al. 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, et al. Ginkgo biloba and ovarian cancer prevention: Epidemiological and biological evidence. Cancer Lett. 2006 Dec 26.

Zeng X, Liu M, Yang Y, et al. Ginkgo biloba for acute ischaemic stroke. Cochrane Database Syst Rev. 2005;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.

Revised: 06/26/2007

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