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© Steven Foster
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Common name: Maidenhair tree
Parts of Ginkgo biloba used and where is Ginkgo biloba grown
is the world’s oldest living species of tree. Individual trees
live as long as 1,000 years. Ginkgo grows most predominantly in the southern and eastern
United States, southern France, China, and Korea. The leaves of the tree are used in modern
herbal medicine.
Historical or traditional use of Ginkgo biloba (may
or may not be supported by scientific studies)
Medicinal use of ginkgo can be traced back almost 5,000 years in Chinese herbal medicine.
The nuts of the tree were most commonly recommended and used to treat respiratory tract
ailments. The use of the leaves is a modern development originating in Europe.
Active constituents of Ginkgo biloba
The medical benefits of extract (GBE) are attributed primarily to
two groups of active constituents: the ginkgo flavone glycosides and the terpene lactones.
Ginkgo flavone glycosides, which typically make up approximately 24% of the extract, are
primarily responsible for GBE’s
antioxidant activity and may mildly inhibit platelet aggregation (stickiness). These two
actions may help GBE prevent circulatory diseases, such as atherosclerosis, and support the brain and central
nervous system.1 In addition to the cardiovascular system, GBE’s antioxidant
action may also extend to the brain and retina of the eye.2 Preliminary trials have
suggested potential benefit for people with
macular degeneration3 and diabetic
retinopathy.4 The terpene lactones found in GBE, known as ginkgolides and
bilobalide, typically make up approximately 6% of the extract. They are associated with
increasing circulation to the brain and other parts of the body and may exert a protective
action on nerve cells.5 GBE regulates the tone and elasticity of blood
vessels,6 making circulation more efficient.7
Ginkgo is also well-known for its effect on memory and thinking (cognitive function). It
may enhance cognitive performance in healthy older adults,8 in people with age-related cognitive decline, and in people with Alzheimer’s disease.
How much Ginkgo biloba is usually taken?
Most clinical trials have used between 120 and 240 mg of GBE (standardized to contain 6%
terpene lactones and 24% flavone glycosides) per day, generally divided into two or three
portions.9 The higher amount (240 mg per day) has been used in some people with
mild-to-moderate Alzheimer’s disease, age-related cognitive decline, intermittent claudication, and resistant depression. GBE may need to be taken for eight to
twelve weeks before desired actions such as cognitive improvement are noticed. Although
nonstandardized leaf and tinctures are available, there is no
well-established amount or use for these forms.
Are there any side effects or interactions with Ginkgo biloba?
Excessive bleeding has been reported in a few individuals taking GBE,10
11 although a cause/effect relationship was not proven. In addition, two elderly
individuals with well-controlled epilepsy developed recurrent seizures within two weeks after
starting GBE.12 Mild headaches lasting for a day or two and mild upset stomach have
been reported in a small number of people using GBE.
Ginkgo leaves are known to contain a group of potentially toxic constituents known as
alkylphenols. The ginkgo extracts known as EGb 761 and LI 1370 have been shown to conform to
the safety limits for these constituents (less that 5 ppm), as set forth by the German
Commission E. Other forms of ginkgo may contain higher concentrations of
alkylphenols.13
One small clinical trial found that ginkgo supplementation for three months increased
secretion of insulin by the pancreas, but did
not affect blood glucose levels, in healthy young adults.14 These results suggest
that the participants may have developed an insensitivity to insulin, a potential concern
because insulin insensitivity may be a precursor to type 2 diabetes. However, this trial does not prove that
ginkgo causes insulin insensitivity, nor does it prove that long-term ginkgo supplementation
increases the risk for any disease. In addition, the results of this trial are not consistent
with other research on ginkgo. Larger and more rigorously designed clinical trials of ginkgo
supplementation have found no significant adverse effects after as many as 12 months of
supplementation.15
People should seek an accurate medical diagnosis prior to self-prescribing GBE. This is
especially important for the elderly, whose circulatory conditions can involve serious
disease, and for people scheduled for surgery, as GBE may affect bleeding time.
Are there any drug
interactions?
Certain medicines may interact with . Refer to drug interactions for a list of those medicines.
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The information presented in Healthnotes is for informational
purposes only. It is based on scientific studies (human, animal, or in
vitro), clinical experience, or traditional usage as cited in each article.
The results reported may not necessarily occur in all individuals. For many of
the conditions discussed, treatment with prescription or over the counter
medication is also available. Consult your doctor, practitioner, and/or
pharmacist for any health problem and before using any supplements or before
making any changes in prescribed medications.
References:
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