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© Steven Foster
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Botanical name: Ginkgo biloba
Common name: Maidenhair tree
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):
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 (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 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 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 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 Ginkgo biloba. Refer to drug interactions for a list of those medicines.
References
1. Drieu K. Preparation and definition of Ginkgo biloba extract.
In: Rokan (Ginkgo biloba): Recent Results in Pharmacology and Clinic. Fünfgeld
EW, ed. Berlin: Springer-Verlag, 32–6.
2. Ferrandini C, Droy-Lefaix MT, Christen Y, eds. Ginkgo biloba
Extract (EGb 761) as a Free Radical Scavenger. Paris: Elsevier, 1993.
3. Lebuisson DA, Leroy L, Rigal G. Treatment of senile macular
degeneration with Ginkgo biloba extract. A preliminary double-blind, drug versus
placebo study. Presse Med 1986;15:1556–8 [in French].
4. Lanthony P, Cosson JP. Evolution of color vision in diabetic
retinopathy treated by extract of Ginkgo biloba. J Fr Ophthalmol 1988;11:671–4
[in French].
5. Krieglstein J. Neuroprotective properties of Ginkgo
biloba—constituents. Zeitschrift Phytother 1994;15:92–6.
6. Clostre F. From the body to the cell membranes: the different levels
of pharmacological action of Ginkgo biloba extract. In: Rokan (Ginkgo biloba):
Recent Results in Pharmacology and Clinic.Fünfgeld EW, ed. Berlin: Springer-Verlag,
1988, 180–98.
7. Jung F, Mrowietz C, Kiesewetter H, Wenzel E. Effect of Ginkgo
biloba on fluidity of blood and peripheral microcirculation in volunteers.
Arzneimittelforschung 1990;40:589–93.
8. Mix JA, Crews WD. An examination of the efficacy of Ginkgo biloba
extract EGb761 on the neuropsychologic functioning of cognitively intact older adults. J
Altern Complement Med 2000;6:219–29.
9. Blumenthal M, Busse WR, Goldberg A, et al, eds. The Complete
Commission E Monographs: Therapeutic Guide to Herbal Medicines. Boston, MA: Integrative
Medicine Communications, 1998, 136–8.
10. Matthews MK Jr. Association of Ginkgo biloba with intracerebral
hemorrhage. Neurology 1998;50:1933–4 [letter].
11. Rosenblatt M, Mindel J. Spontaneous hyphema associated with ingestion
of Ginkgo biloba extract. N Engl J Med 1997;336:1108 [letter].
12. Granger AS. Ginkgo biloba precipitating epileptic seizures. Age
Ageing 2001;30:523–5.
13. Siegers CP. Cytotoxicity of alkylphenols from Ginkgo biloba.
Phytomedicine 1999;6:281–3.
14. Kudolo GB. The effect of 3-month ingestion of Ginkgo biloba
extract on pancreatic ß-cell function in response to glucose loading in normal
glucose-tolerant individuals. J Clin Pharmacol 2000;40:647–54.
15. 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;278:1327–32.
Copyright © 2004 Healthnotes, Inc. All rights reserved.
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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. Information expires March 2005.
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