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Ginkgo
biloba
Common name:
Maidenhair tree
Botanical name:
Ginkgo
biloba
Parts used and where
grown
Ginkgo biloba 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.
Ginkgo
biloba has been used in connection with the
following conditions (refer to the
individual health concern for complete
information):
| Health Concerns |
|
Age-related cognitive decline
(ARCD)
Alzheimer’s disease
(early-stage)
Glaucoma (normal tension
glaucoma)
Intermittent
claudication |
|
Altitude sickness
(prevention)
Depression (for elderly
people)
Erectile dysfunction (of
vascular origin)
Macular
degeneration
Schizophrenia (in combination
with haloperidol)
Vertigo
Vitiligo |
|
Asthma
Atherosclerosis
Deafness, acute
cochlear
Memory enhancement (in
healthy adults)
Méničre’s
disease
Migraine
headaches
Multiple sclerosis
(injections)
Premenstrual
syndrome
Raynaud’s
disease
Retinopathy
Tinnitus
Type 1
diabetes
Type 2
diabetes |
Historical
or traditional use (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
The medical benefits of Ginkgo
biloba extract 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 ginkgo’s
antioxidant activity and may mildly inhibit platelet
aggregation (stickiness). These two actions may help
ginkgo prevent circulatory diseases, such as
atherosclerosis, and support the brain and central
nervous system. In addition to the cardiovascular
system, ginkgo’s antioxidant action may also extend to
the brain and retina of the eye. Preliminary trials have
suggested potential benefit for people with macular
degeneration and diabetic retinopathy. The terpene
lactones found in ginkgo extracts, 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. ginkgo
regulates the tone and elasticity of blood vessels,
making circulation more
efficient.
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 is usually
taken?
Most clinical trials have used between
120 and 240 mg of ginkgo (standardized to contain 6%
terpene lactones and 24% flavone glycosides) per day,
generally divided into two or three portions. 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. Ginkgo may need to be taken for
eight to twelve weeks before desired actions such as
cognitive improvement are noticed. Although
nonstandardized Ginkgo biloba leaf and
tinctures are available, there is no well-established
amount or use for these
forms.
Are there any side effects or
interactions?
Excessive bleeding has been reported in a
few individuals taking ginkgo, 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
ginkgo. Mild headaches lasting for a day or two and mild
upset stomach have been reported in a small number of
people using ginkgo.
Ginkgo leaves are known to contain a
group of potentially toxic constituents known as
alkylphenols. To reduce the potential for adverse
effects, the German Commission E Monograph requires that
ginkgo products for human consumption contain less than
5 parts per million of alkylphenols.
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. 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.
People should seek an accurate medical
diagnosis prior to self-prescribing ginkgo. This is
especially important for the elderly, whose circulatory
conditions can involve serious disease, and for people
scheduled for surgery, as ginkgo may affect bleeding
time. | |
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