Plant Description

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 smell bad. The fruit has an inner seed, which may be poisonous. Ginkgos are tough, hardy trees and are sometimes planted along urban streets in the United States. The leaves turn brilliant colors in the fall.

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) made from the dried green leaves. This standardized extract is highly concentrated and seems to treat health problems (particularly circulatory problems) better than the non-standardized leaf alone.

What is it Made of?

Scientists have found more than 40 components in ginkgo. Only two are believed to act as medicine: flavonoids and terpenoids. Flavonoids are plant-based antioxidants. Laboratory and animal studies show 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 people, ginkgo is used for the following:

Dementia and Alzheimer disease

Ginkgo is widely used in Europe for treating dementia. At first, doctors thought it helped because it improves blood flow to the brain. Now research suggests it may protect nerve cells that are damaged in Alzheimer disease. Several studies show that ginkgo has a positive effect on memory and thinking in people with Alzheimer disease or vascular dementia.

Studies suggest that ginkgo may help people with Alzheimer disease:

• Improve thinking, learning, and memory (cognitive function)
• Have an easier time performing daily activities
• Improve social behavior
• Have fewer feelings of depression

Several studies have found that ginkgo may work as well as some prescription Alzheimer disease medications to delay the symptoms of dementia. It has not been tested against all of the drugs prescribed to treat Alzheimer disease.

In 2008, a well-designed study with more than 3,000 elderly people found that ginkgo was no better than placebo in preventing dementia or Alzheimer disease.

Intermittent claudication

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 8 studies showed that people taking ginkgo tended to walk about 34 meters farther than those taking placebo. In fact, ginkgo has been shown to work as well as a prescription medication in improving pain-free walking distance. However, regular walking exercises work better than ginkgo in improving walking distance.

Anxiety

One preliminary study found that a special formulation of ginkgo extract called EGB 761 might help relieve anxiety. People with generalized anxiety disorder and adjustment disorder who took this specific extract had fewer anxiety symptoms than those who took placebo.

Glaucoma

One small study found that people with glaucoma who took 120 mg of ginkgo daily for 8 weeks had improvements in their vision.

Memory and thinking

Ginkgo is widely touted as a "brain herb." Some studies show that it does help improve memory in people with dementia. It is 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. Some studies have found that ginkgo helps improve memory and thinking in young and middle-aged people who are healthy. And preliminary studies suggest it may be useful in the treatment of Attention Deficit Hyperactivity Disorder (ADHD). The dose that works best seems to be 240 mg per day. Ginkgo is often added to nutrition bars, soft drinks, and fruit smoothies to boost memory and enhance mental performance, although such small amounts probably do not help.

Macular degeneration

The flavonoids found in ginkgo may help stop or reduce some problems with the retina, the back part of the eye. Macular degeneration, often called age-related macular degeneration or AMD, is an eye disease that affects the retina. The number one cause of blindness in the Unites States, AMD is a degenerative eye disease that gets worse as time goes on. Some studies suggest that ginkgo may help preserve vision in those with AMD.

Premenstrual syndrome (PMS)

Two studies with a somewhat complicated dosing schedule found that ginkgo helped reduce PMS symptoms. Women in the studies took a special extract of ginkgo beginning on day 16 of their menstrual cycle and stopped taking it after day 5 of their next cycle, then took it again on day 16.

Raynaud's phenomenon

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.

Available Forms

• Standardized extracts containing 24 to 32% flavonoids (also known as flavone glycosides or heterosides) and 6 to 12% terpenoids (triterpene lactones)
• Capsules
• Tablets
• Liquid extracts (tinctures, fluid extracts, and glycerites)
• Dried leaf for teas

How to Take it

Pediatric

Ginkgo should not be given to children.

Adult

Memory problems and Alzheimer disease: Many studies have used 120 to 240 mg daily in divided doses, standardized to contain 24 to 32% flavone glycosides (flavonoids or heterosides) and 6 to 12% triterpene lactones (terpenoids).

Intermittent claudication: Studies have used 120 to 240 mg per day.

It can take 4 to 6 weeks to see any effects from ginkgo. Ask your doctor to help you find the right dose.

Precautions

The use of herbs is a time-honored approach to strengthening the body and treating disease. However, herbs 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, people have reported stomach upset, headaches, skin reactions, and dizziness.

There have been reports of internal bleeding in people who take ginkgo. It is not clear whether the bleeding was due to ginkgo or some other reason, such as a combination of ginkgo and blood-thinning drugs. Ask your doctor before taking ginkgo if you also take blood-thinning drugs.

Stop taking ginkgo 1 to 2 weeks before surgery or dental procedures due to the risk of bleeding. Always alert your doctor or dentist that you take ginkgo.

People who have epilepsy should not take ginkgo, because 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.

Possible Interactions

Ginkgo may interact with prescription and non-prescription medications. If you are taking any of the following medications, you should not use ginkgo without talking to your doctor first.

Medications broken down by the liver: Ginkgo can interact with medications that are processed through the liver. Because many medications are broken down by the liver, if you take any prescription medications ask your doctor before taking ginkgo.

Seizure medications (anticonvulsants): High doses of ginkgo could interfere with the effectiveness of anti-seizure drugs. These drugs include carbamazepine (Tegretol) and valproic acid (Depakote).

Antidepressants: Taking ginkgo along with a kind of antidepressant called selective serotonin reuptake inhibitors (SSRIs) may increase the risk of serotonin syndrome, a life-threatening condition. Also, ginkgo may strengthen both the good and bad effects of antidepressants known as MAOIs, such as phenelzine (Nardil). SSRIs include:

• Citalopram (Celexa)
• Escitalopram (Lexapro)
• Fluoxetine (Prozac)
• Fluvoxamine (Luvox)
• Paroxetine (Paxil)
• Sertraline (Zoloft)

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 heart rhythm problems.

Blood-thinning medications: Ginkgo may raise the risk of bleeding, especially if you take blood-thinners, such as warfarin (Coumadin), clopidogrel (Plavix), and aspirin.

Alprazolam (Xanax): Ginkgo may make Xanax less effective, and interfere with the effectiveness of other drugs taken to treat anxiety.

Ibuprofen (Advil, Motrin): Like ginkgo, the nonsteroidal anti-inflammatory drug (NSAID) ibuprofen also raises the risk of bleeding. Bleeding in the brain has been 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 person with Alzheimer disease going into a coma after taking ginkgo and trazodone (Desyrel), an antidepressant medication.

Supporting Research

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