Ginkgo (Ginkgo biloba) is one of the oldest living tree species and
its leaves are among the most extensively studied botanicals in use today.
Unlike many other medicinal herbs, ginkgo leaves are not frequently used in
their crude state, but rather, in the form of a concentrated, standardized
ginkgo biloba extract (GBE). In Europe, GBE is among the best-selling herbal
medications and it ranks within the top five of all prescriptions written in
France and Germany.
Ginkgo has been used in traditional medicine to treat circulatory disorders
and enhance memory. Scientific studies throughout the years lend support to
these traditional uses. Emerging evidence suggests that GBE may be particularly
effective in treating ailments associated with decreased blood flow to the
brain, particularly in elderly individuals. Laboratory studies have shown that
GBE improves blood circulation by dilating blood vessels and reducing the
stickiness of blood platelets.
Ginkgo leaves also contain two types of chemicals (flavonoids and terpenoids)
believed to have potent antioxidant properties. Antioxidants are substances that
scavenge free radicals -- damaging compounds in the body that alter cell
membranes, tamper with DNA, and even cause cell death. Free radicals occur
naturally in the body, but environmental toxins (including ultraviolet light,
radiation, cigarette smoking, and air pollution) can also increase the number of
these damaging particles. Free radicals are believed to contribute to a number
of health problems including heart disease and cancer as well as Alzheimer's
disease and other forms of dementia. Antioxidants such as those found in ginkgo
can neutralize free radicals and may reduce or even help prevent some of the
damage they cause.
Based on studies conducted in laboratories, animals, and humans, professional
herbalists may recommend ginkgo for the following health problems:
Dementia and Alzheimer's Disease Ginkgo is widely used in
Europe for treating dementia. The reason that ginkgo is thought to be helpful
for preventing or treating these brain disorders is because it improves blood
flow in the brain and because of its antioxidant properties. Although many of
the clinical trials have been scientifically flawed, the evidence that ginkgo
may improve thinking, learning, and memory in people with Alzheimer's disease
(AD) has been highly promising.
Clinical studies suggest that ginkgo provides the following benefits for
people with AD:
Improvement in thinking, learning, and memory
Improvement in activities of daily living
Improvement in social behavior
Fewer feelings of depression
One recent study also found that ginkgo may be as effective as leading AD
medications in delaying the symptoms of dementia in people with this
debilitating condition. In addition, ginkgo is sometimes used preventively
because it may delay the onset of AD in someone who is at risk for this type of
dementia (for example, family history).
Eye problems The flavonoids found in ginkgo may help halt or
lessen some retinal problems (that is, problems to the back part of the eye).
Retinal damage has a number of potential causes, including diabetes and macular
degeneration. Macular degeneration (often called age-related macular
degeneration or ARMD) is a progressive, degenerative eye disease that tends to
affect older adults and is the number one cause of blindness in the United
States. Studies suggest that gingko may help preserve vision in those with ARMD.
Intermittent Claudication Because ginkgo is reputed to improve
blood flow, this herb has been studied in people with intermittent claudication
(pain caused by inadequate blood flow [atherosclerosis] to the legs). People
with intermittent claudication have difficulty walking without suffering extreme
pain. An analysis of eight published studies revealed that people taking ginkgo
tend to walk roughly 34 meters farther than those taking placebo. In fact,
ginkgo has been shown to be as effective as a leading medication in improving
pain-free walking distance. However, regular walking exercises are more
beneficial than ginkgo in improving walking distance.
Memory Impairment Ginkgo is widely touted as a "brain herb"
and is commonly added to nutrition bars and fruit smoothies to boost memory and
enhance cognitive performance. Researchers recently reviewed all of the
high-quality published studies on ginkgo and mild memory impairment (in other
words, people without Alzheimer's or other form of dementia), and concluded that
ginkgo was significantly more effective than placebo in enhancing memory and
cognitive function. Despite the encouraging findings, some researchers speculate
that more high-quality research, involving larger numbers of people, is needed
before ginkgo can be recommended as a memory enhancer to otherwise healthy
Tinnitus Given that nerve damage and certain blood vessel
disorders can lead to tinnitus (the perception of ringing, hissing, or other
sound in the ears or head when no external sound is present), some researchers
have investigated whether ginkgo relieves symptoms of this hearing disorder.
Although the quality of most studies was poor, the reviewers concluded that
ginkgo moderately relieves the loudness of the tinnitus sound. However, a recent
well-designed study including 1,121 people with tinnitus found that ginkgo
(given 3 times daily for 3 months) was no more effective than placebo in
relieving symptoms of tinnitus. Given these conflicting findings, the
therapeutic value of ginkgo for tinnitus remains uncertain. In general, tinnitus
is a very difficult problem to treat. Talk to your doctor about whether a trial
of ginkgo to alleviate this frustrating symptom may be safe and worthwhile for
Other In addition to these health problems, professional
herbalists may also recommend ginkgo for a variety of other ailments including
altitude sickness, asthma, depression, disorientation, headaches, high blood
pressure, erectile dysfunction, and vertigo.
Ginkgo biloba is the oldest living tree species. A single tree can live as
long as 1,000 years and grow to a height of 120 feet. It has short branches with
fan-shaped leaves and inedible fruits that produce a strong odor. The fruit
contains an edible inner seed.
Although Chinese herbal medicine has used both the ginkgo leaf and seed for
centuries, modern research has focused on the standardized Ginkgo biloba extract
(GBE), which is prepared from the dried green leaves. This extract is highly
concentrated and much more effective in treating health problems (particularly
circulatory ailments) than the leaf alone.
What's It Made Of?
More than 40 components of ginkgo have been identified but only two are
believed to be responsible for the herb's beneficial effects -- flavonoids and
terpenoids. As described earlier, flavonoids (such as quercetin) have potent
antioxidant effects. Laboratory and animal studies have shown that flavonoids
protect the nerves, heart muscle, and retina from damage. Terpenoids (such as
ginkgolides) improve blood flow by dilating blood vessels and reducing the
stickiness of platelets.
Ginkgo biloba extract (GBE) standardized to contain 24% flavonoids and
How to Take It
There are no known scientific reports on the pediatric use of ginkgo.
Therefore, it is not currently recommended for children.
Initial results often take 4 to 6 weeks, but should continue to
accumulate beyond that period. You may not see any dramatic changes for six
GBE: 120 mg daily in two or three divided doses of 50:1 extract
standardized to 24% flavone glycosides (flavonoids). If more serious dementia or
Alzheimer's disease is present, up to 240 mg daily in two or three divided doses
may be necessary.
Tincture (1:5): 2 to 4 mL three times a day
The use of herbs is a time-honored approach to strengthening the body and
treating disease. Herbs, however, contain active substances that can trigger
side effects and interact with other herbs, supplements, or medications. For
these reasons, herbs should be taken with care, under the supervision of a
practitioner knowledgeable in the field of botanical medicine.
GBE is considered to be safe and side effects are rare. In a few cases,
gastrointestinal upset, headaches, skin reactions, and dizziness were reported.
Because gingko decreases platelet aggregation (stickiness), there is some
concern that it may increase risk of intracranial (brain) hemorrhage. In fact,
there have been several reports of bleeding complications associated with ginkgo
use. However, it is not clear whether ginkgo or another factor (such as the
combination of ginkgo and blood-thinning medications including aspirin) caused
the bleeding complications.
Pregnant and breastfeeding women should avoid using ginkgo preparations. In
addition, ginkgo use should be discontinued at least 36 hours prior to surgery
due to the risk of bleeding complications.
Do not ingest Ginkgo biloba fruit.
If you are currently being treated with any of the following medications, you
should not use ginkgo without first talking to your healthcare provider:
Anticonvulsant medications High doses of Ginkgo biloba could
decrease the effectiveness of anticonvulsant therapy in patients taking
carbamazepine or valproic acid to control seizures.
Blood-thinning medications Ginkgo has blood-thinning
properties and therefore should not be used if you are taking anticoagulant
(blood-thinning) medications, such as aspirin, clopidogrel, dipyridamole,
heparin, ticlopidine, or warfarin.
Cylosporine Ginkgo biloba may be beneficial during treatment
with cyclosporine because of its ability to protect cell membranes from damage.
Monoamine oxidase inhibitors (MAOIs) Ginkgo may enhance the
effects (both good and bad) of antidepressant medications known as MAOIs, such
as phenelzine and tranylcypromine.
Papaverine The combination of papaverine and ginkgo may be
effective for the treatment of erectile dysfunction in patients who do not
respond to papaverine alone.
Thiazide diuretics Although there has been one literature
report of increased blood pressure associated with the use of ginkgo during
treatment with thiazide diuretics, this interaction has not been verified by
clinical trials. Nevertheless, you should consult with your healthcare provider
before using ginkgo if you are taking thiazide diuretics.
Trazodone Additionally, there has been a report of an adverse
interaction between ginkgo and trazodone, an antidepressant medication, that
resulted in an elderly patient going into a coma.
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Review Date: April 2002
Reviewed By: Participants in the review process include: Jacqueline A. Hart, MD,
Department of Internal Medicine, Newton-Wellesley Hospital, Harvard University
and Senior Medical Editor Integrative Medicine, Boston, MA; Gary Kracoff, RPh
(Pediatric Dosing section February 2001), Johnson Drugs, Natick, MA; Steven
Ottariono, RPh, Veteran's Administrative Hospital, Londonderry, NH; Leonard
Wisneski, MD, FACP (April 1999), George Washington University, Rockville, MD;
Tom Wolfe, P.AHG (April 1999), Smile Herb Shop, College Park, MD; Elizabeth
Wotton, ND (April 1999), private practice, Sausalito, CA. All interaction
sections have also been reviewed by a team of experts including Joseph Lamb, MD
(July 2000), The Integrative Medicine Works, Alexandria, VA;Enrico Liva, ND, RPh
(August 2000), Vital Nutrients, Middletown, CT; Brian T Sanderoff, PD, BS in
Pharmacy (March 2000), Clinical Assistant Professor, University of Maryland
School of Pharmacy; President, Your Prescription for Health, Owings Mills, MD;
R. Lynn Shumake, PD (March 2000), Director, Alternative Medicine Apothecary,
Blue Mountain Apothecary & Healing Arts, University of Maryland Medical
Center, Glenwood, MD; Ira Zunin, MD, MPH, MBA (July 2000), President and
Chairman, Hawaii State Consortium for Integrative Medicine, Honolulu,
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