Ginkgo biloba

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):

Science Ratings	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) Ménière’s disease Migraine headaches Multiple sclerosis (injections) Premenstrual syndrome Raynaud’s disease Retinopathy Tinnitus Type 1 diabetes Type 2 diabetes
Reliable and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit. For a herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.

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. 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.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
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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.

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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 chemist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires March 2007.