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Ginkgo biloba
Common name: Maidenhair tree
Botanical name: Ginkgo biloba
© Steven Foster
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 an 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 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.1 In addition to the cardiovascular system, ginkgo’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 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.5 ginkgo 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 ginkgo (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. 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,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 ginkgo.12 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.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 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.
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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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 September 2008.