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Ginkgo (Ginkgo biloba) is one of the oldest living tree species and its leaves are among the most extensively studied herbs in use today. In Europe and the United States, ginkgo supplements are among the best-selling herbal medications. It consistently ranks as a top medicine prescribed in France and Germany.
Ginkgo has been used in traditional medicine to treat blood disorders and enhance memory. Scientific studies throughout the years have found evidence that supports these claims. Although not all studies agree, ginkgo may be help treat dementia (including Alzheimer's disease) and intermittent claudication, or poor circulation in the legs. It also shows promise for enhancing memory in older adults. Laboratory studies have shown that ginkgo improves blood circulation by dilating blood vessels and reducing the stickiness of blood platelets.
Ginkgo leaves contain two types of chemicals (flavonoids and terpenoids) believed to have potent antioxidant properties. Antioxidants are substances that scavenge free radicals -- compounds in the body that damage cell membranes, tamper with DNA, and even cause cell death. Free radicals are believed to contribute to health problems including heart disease and cancer as well as Alzheimer's disease and other forms of dementia. Antioxidants such as those found in ginkgo can help neutralize free radicals and may reduce or even help prevent some of the damage they cause.
Ginkgo biloba is the oldest living tree species. A single tree can live as long as 1,000 years and grow to a height of 120 feet. It has short branches with fan-shaped leaves and inedible fruits that produce a strong odor. The fruit contains an inner seed, and there has been a report of a human poisoning from ingesting the seed. Ginkgos are tough, hardy trees and are sometimes planted along urban streets in the United States.
Although Chinese herbal medicine has used both the ginkgo leaf and seed for thousands of years, modern research has focused on the standardized Ginkgo biloba extract (GBE), which is made from the dried green leaves. This standardized extract is highly concentrated and seems to be more effective in treating health problems (particularly circulatory ailments) than the non-standardized leaf alone.
What's It Made Of?
More than 40 components from the ginkgo tree have been identified, but only two are believed to act as medicine: flavonoids and terpenoids. Flavonoids are plant-based antioxidants. Laboratory and animal studies have shown that flavonoids protect the nerves, heart muscle, blood vessels, and retina from damage. Terpenoids (such as ginkgolides) improve blood flow by dilating blood vessels and reducing the stickiness of platelets.
Medicinal Uses and Indications
Based on studies conducted in laboratories, animals, and humans, ginkgo is used for the following:
Dementia and Alzheimer's disease
Ginkgo is widely used in Europe for treating dementia. It was first used because it improves blood flow to the brain. Now further study suggests it may directly protect nerve cells that are damaged in Alzheimer's disease. A number of studies have found that ginkgo has a positive effect on memory and thinking in people with Alzheimer's or vascular dementia.
Clinical studies suggest that ginkgo may have the following benefits for people with Alzheimer's disease:
Several studies have found that ginkgo may work as well as prescription Alzheimer's medications in delaying the symptoms of dementia.
However, one of the longest and best-designed studies found ginkgo was no better than placebo in reducing Alzheimer's symptoms. In a 2008 study, 176 people in the United Kingdom with Alzheimer's took either ginkgo or placebo for 6 months. At the end of the study there was no difference in mental function or quality of life between the groups.
Ginkgo is sometimes suggested to prevent Alzheimer's and dementia, as well, and some studies have suggested it might be helpful. But in 2008, a well-designed study (the GEM study) with more than 3,000 elderly participants found the ginkgo was no better than placebo in preventing dementia or Alzheimer's.
Because ginkgo improves blood flow, it has been studied in people with intermittent claudication, or pain caused by reduced blood flow to the legs. People with intermittent claudication have a hard time walking without feeling extreme pain. An analysis of eight studies revealed that people taking ginkgo tend to walk about 34 meters farther than those taking placebo. In fact, ginkgo has been shown to be as effective as a prescription medication in improving pain-free walking distance. However, regular walking exercises work better than ginkgo in improving walking distance.
One small study found that people with glaucoma who took 120 mg of ginkgo daily for 8 weeks had improvements in their vision.
Ginkgo is widely touted as a "brain herb." It has been studied to see whether it can improve memory in people with dementia, and some studies found it did help. It's not as clear whether ginkgo helps memory in healthy people who have normal, age-related memory loss. Some studies have found slight benefits, while other studies have found no effect on memory. The most effective dose seems to be 240 mg per day. Ginkgo is commonly added to nutrition bars, soft drinks, and fruit smoothies to boost memory and enhance mental performance, although it's unlikely that such small amounts of ginkgo would work.
The flavonoids found in ginkgo may help stop or lessen some retinal problems -- problems with the back part of the eye. Macular degeneration, often called age-related macular degeneration or ARMD, is an eye disease that affects the retina. It is a progressive, degenerative eye disease that tends to affect older adults and is the number one cause of blindness in the United States. Some studies suggest that ginkgo may help preserve vision in those with ARMD.
Nerve damage and certain blood vessel disorders can lead to tinnitus -- ringing, hissing, or other sound in the ears or head. Because ginkgo improves circulation, it has been studied to see whether it can treat tinnitus. A few poorly designed studies found it might reduce the loudness of the sound. However, a well-designed study including 1,121 people with tinnitus found that ginkgo was no better than placebo in relieving tinnitus symptoms. In general, tinnitus is a very difficult problem to treat.
One well-designed study found that people with Raynaud’s phenomenon who took ginkgo over a 10-week period had fewer symptoms than those who took placebo. More studies are needed.
How to Take It
Ginkgo is not generally used in children.
Initial results often take 4 - 6 weeks, but should grow stronger beyond that period.
Memory impairment and cardiovascular function: Generally, 120 mg daily in divided doses, standardized to contain 24 - 32% flavone glycosides (flavonoids or heterosides) and 6 - 12% triterpene lactones (terpenoids). If more serious dementia or Alzheimer's disease is present, up to 240 mg daily, in 2 or 3 divided doses, may be necessary.
Intermittent claudication: 120 - 240 mg per day
The use of herbs is a time-honored approach to strengthening the body and treating disease. Herbs, however, contain components that can trigger side effects and interact with other herbs, supplements, or medications. For these reasons, herbs should be taken with care, under the supervision of a health care provider qualified in the field of botanical medicine.
Ginkgo usually has few side effects. In a few cases, stomach upset, headaches, skin reactions, and dizziness were reported.
There have been a number of reports of internal bleeding in people who take ginkgo. However, it’s not clear whether the bleeding was due to ginkgo or some other reasons, such as a combination of ginkgo and blood-thinning drugs. Researchers aren’t sure, because different studies have found different results. You should ask your doctor before taking ginkgo if you also take blood-thinning drugs.
If you take ginkgo, you should stop taking it at least 36 hours before surgery or dental procedures due to the risk of bleeding. Tell your doctor or dentist that you take ginkgo.
People who have epilepsy should not take ginkgo, because there is concern that it might cause seizures.
Pregnant and breastfeeding women should not take ginkgo.
People who have diabetes should ask their doctor before taking ginkgo.
Do not eat Ginkgo biloba fruit or seed.
Ginkgo may interact with some prescription and non-prescription medications. If you are taking any of the following medications, you should not use ginkgo without first talking to your health care provider:
Medications metabolized by the liver -- Ginkgo can interact with some medications that are processed through the liver. If you take any prescription medications, ask your doctor before taking ginkgo.
Seizure medications (anticonvulsants) -- High doses of ginkgo could make drugs to control seizures, such as carbamazepine (Tegretol) or valproic acid (Depakote), less effective.
Antidepressants -- Taking ginkgo along with a kind of antidepressant called selective serotonin reuptake inhibitors (SSRIs) may increase the risk of serotonin syndrome, a potentially fatal condition. Ginkgo may strengthen both the good and bad effects of antidepressant medications known as MAOIs, such as phenelzine (Nardil). SSRIs include:
Medications for high blood pressure -- Ginkgo may lower blood pressure, so taking it with blood pressure medications may cause blood pressure to drop too low. There has been a report of an interaction between ginkgo and nifedipine (Procardia), a calcium channel blocker used for blood pressure and arrhythmias.
Blood-thinning medications -- Ginkgo may raise the risk of bleeding, especially if you take blood-thinners such as warfarin (Coumadin), clopidogrel (Plavix), and aspirin.
Ibuprofen (Advil, Motrin) -- Like ginkgo, the nonsteroidal anti-inflammatory drug (NSAID) ibuprofen also raises the risk of bleeding. There has been bleeding in the brain reported when using a ginkgo product and ibuprofen.
Medications to lower blood sugar -- Ginkgo may raise or lower insulin levels and blood sugar levels. If you have diabetes, you should not use ginkgo without first talking to your doctor.
Cylosporine -- Ginkgo biloba may help protect the cells of the body during treatment with the drug cyclosporine, which suppresses the immune system.
Thiazide diuretics (water pills) -- There is one report of a person who took a thiazide diuretic and ginkgo developing high blood pressure. If you take thiazide diuretics, ask your doctor before taking ginkgo.
Trazodone -- There is one report of an elderly Alzheimer's patient going into a coma after taking ginkgo and trazodone (Desyrel), an antidepressant medication.
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Review Date: 12/13/2010
Reviewed By: Steven D. Ehrlich, NMD, Solutions Acupuncture, a private practice specializing in complementary and alternative medicine, Phoenix, AZ. Review provided by VeriMed Healthcare Network.
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