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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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