Ginkgo (Ginkgo biloba) is one of the oldest living tree species and its leaves are among the most extensively studied botanicals in use today. Unlike many other medicinal herbs, ginkgo leaves are not frequently used in their crude state, but rather, in the form of a concentrated, standardized ginkgo biloba extract (GBE). In Europe and the United States, ginkgo supplements are among the best-selling herbal medications and it consistently ranks as a top medicine prescribed in France and Germany.

Ginkgo has been used in traditional medicine to treat circulatory disorders and enhance memory. Scientific studies throughout the years lend support to these traditional uses. Emerging evidence suggests that GBE may be particularly effective in treating ailments associated with decreased blood flow to the brain, particularly in elderly individuals. Laboratory studies have shown that GBE improves blood circulation by dilating blood vessels and reducing the stickiness of blood platelets.

Ginkgo leaves also contain two types of chemicals (flavonoids and terpenoids) believed to have potent antioxidant properties. Antioxidants are substances that scavenge free radicals -- damaging compounds in the body that alter cell membranes, tamper with DNA, and even cause cell death. Free radicals occur naturally in the body, but environmental toxins (including ultraviolet light, radiation, cigarette smoking, and air pollution) can also increase the number of these damaging particles. Free radicals are believed to contribute to a number of 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 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.

Although Chinese herbal medicine has used both the ginkgo leaf and seed for centuries, modern research has focused on the standardized Ginkgo biloba extract (GBE), which is prepared from the dried green leaves. This standardized extract is highly concentrated and seems to be clinically more effective in treating health problems (particularly circulatory ailments) than the non-standardized leaf alone.

More than 40 components isolated from the ginkgo tree have been identified, but only two are believed to be responsible for the herb's beneficial effects in humans -- flavonoids and terpenoids. Flavonoids (such as quercetin and rutin) have potent antioxidant effects. 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.

Based on studies conducted in laboratories, animals, and humans, many health care professionals may recommend ginkgo for the following health problems:

Dementia and Alzheimer's Disease

Ginkgo is widely used in Europe for treating dementia. It use is primarily due to its ability to improve blood flow to the brain and because of its antioxidant properties. The evidence that ginkgo may improve thinking, learning, and memory in people with Alzheimer's disease (AD) has been highly promising.

Clinical studies suggest that ginkgo may provide the following benefits for people with AD:

• Improvement in thinking, learning, and memory (cognitive function)
• Improvement in activities of daily living
• Improvement in social behavior
• Fewer feelings of depression

Several studies have found that ginkgo may be as effective as leading AD medications in delaying the symptoms of dementia in people with this debilitating condition. In addition, ginkgo is sometimes used preventively because it may delay the onset of AD in someone who is at risk for this type of dementia (for example, family history).

Eye problems

The flavonoids found in ginkgo may help halt or lessen some retinal problems (that is, problems to the back part of the eye). Retinal damage has a number of potential causes, including diabetes and macular degeneration. Macular degeneration (often called age-related macular degeneration or ARMD) is a progressive, degenerative eye disease that tends to affect older adults and is the number one cause of blindness in the United States. Studies suggest that gingko may help preserve vision in those with ARMD.

Intermittent Claudication

Because ginkgo is reported to improve blood flow, this herb has been studied in people with intermittent claudication (pain caused by inadequate blood flow to the legs). People with intermittent claudication have difficulty walking without suffering extreme pain. An analysis of eight published studies revealed that people taking ginkgo tend to walk roughly 34 meters farther than those taking placebo. In fact, ginkgo has been shown to be as effective as a leading medication in improving pain-free walking distance. However, regular walking exercises are more beneficial than ginkgo in improving walking distance.

Memory Impairment

Ginkgo is widely touted as a "brain herb." Researchers recently reviewed all of the high-quality published studies on ginkgo and mild memory impairment (in other words, people without Alzheimer's or other form of dementia), and concluded that ginkgo was significantly more effective than placebo in enhancing memory and cognitive function. Ginkgo is commonly added to nutrition bars, soft drinks, and fruit smoothies to boost memory and enhance cognitive performance, although there is debate over whether the small amounts of ginkgo found in these products are effective.

Tinnitus

Given that nerve damage and certain blood vessel disorders can lead to tinnitus (the perception of ringing, hissing, or other sound in the ears or head when no external sound is present), some researchers have investigated whether ginkgo relieves symptoms of this hearing disorder. Although the quality of most studies was poor, the reviewers concluded that ginkgo moderately relieves the loudness of the tinnitus sound. However, a well-designed study including 1,121 people with tinnitus found that ginkgo (given 3 times daily for 3 months) was no more effective than placebo in relieving symptoms of tinnitus. Given these conflicting findings, the therapeutic value of ginkgo for tinnitus remains uncertain. In general, tinnitus is a very difficult problem to treat.

Other uses

In addition to these health problems, health care professionals may also recommend ginkgo for a variety of other ailments, including altitude sickness, asthma, depression, disorientation, headaches, high blood pressure, erectile dysfunction, and vertigo.

• A clinical study found that a standardized ginkgo extract may reduce the side effects of menopause as well as risk factors for osteoporosis and cardiovascular disease. Women are becoming more reluctant to use pharmaceutical hormone replacement therapy (HRT) due to its undesirable side effects, such as irregular bleeding and an increased risk of breast cancer. Several human studies have reported that a standardized ginkgo extract has estrogenic activity and might be suitable as an alternative to HRT.
• A standardized ginkgo extract was reported to significantly improve functional measures (such as coordination, energy level, strength, mental performance, mood, and sensation) in 22 individuals with multiple sclerosis (MS).

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

Pediatric

Ginkgo is not routinely used in children by the medical community. Therefore, it is not currently recommended to use ginkgo in children under 12.

Adult

Initial results often take 4 - 6 weeks, but should continue to accumulate 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.

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.

GBE is considered to be safe, and side effects are rare. In a few cases, gastrointestinal upset, headaches, skin reactions, and dizziness were reported.

Because gingko decreases platelet aggregation (stickiness), there is some concern that it may increase risk of intracranial (brain) hemorrhage. In fact, there have been several reports of bleeding complications associated with ginkgo use. However, it is not clear whether ginkgo or another factor (such as the combination of ginkgo and blood-thinning medications including aspirin and non-steroidal anti-inflammatory agents such as ibuprofen) caused the bleeding complications. One human study found that a ginkgo extract significantly prolonged bleeding time when given along with cilostazol (Pletal), a commonly used medication that inhibits platelet aggregation.

Pregnant and breastfeeding women should avoid using ginkgo preparations. In addition, ginkgo use should be discontinued at least 36 hours prior to surgery due to the risk of bleeding complications.

Do not ingest Ginkgo biloba fruit or seed.

Ginkgo may alter the metabolism and effectiveness of some prescription and non-prescription medications. If you are being treated with any of the following medications, you should not use ginkgo without first talking to your health care provider:

Anticonvulsant medications -- High doses of ginkgo could decrease the effectiveness of anticonvulsant therapy, such as carbamazepine (Tegretol) or valproic acid (Depakote), in controlling seizures.

Antidepressant medications -- Taking ginkgo along with selective serotonin reuptake inhibitor (SSRIs) antidepressants -- including fluoxetin (Prozac), sertraline (Zoloft), paroxetine (Paxil), and escitalopram (Lexapro) -- may cause serotonin syndrome. This condition is characterized by rigidity, tachycardia (fast heart rate), hyperthermia (low body temperature), restlessness, and diaphoresis (sweating). Ginkgo may enhance the effects (both good and bad) of antidepressant medications known as MAOIs, such as phenelzine (Nardil).

Antihypertensive medications -- Ginkgo may decrease blood pressure, so use of ginkgo along with prescription antihypertensive medications should be monitored by a health care provider. There has been a report of an interaction between ginkgo and nifedipine (Procardia), a calcium channel blocking drug used for blood pressure and arrhythmias.

Blood-thinning medications -- Ginkgo has blood-thinning properties and therefore should not be used if you are taking anticoagulant (blood-thinning) medications, such as aspirin, clopidogrel (Plavix), dipyridamole (Persantine), heparin, ticlopidine (Ticlid), or warfarin (Coumadin). There has been bleeding in the brain reported when using a ginkgo product and ibuprofen (Advil), a non-steroidal antiinflammatory drug (NSAID).

Blood sugar lowering medications -- Ginkgo was reported to increase insulin levels in healthy subjects and to decrease insulin levels in diabetic patients. Use ginkgo supplements under the supervision of a health care provider if you are diabetic and taking insulin or oral blood sugar lowering drugs.

Cylosporine -- Ginkgo biloba may help protect the cells of the body during treatment with the immunosuppressive (decreases immunity) drug cyclosporine.

Thiazide diuretics -- Although there has been one literature report of increased blood pressure associated with the use of ginkgo during treatment with thiazide diuretics, this interaction has not been verified by clinical trials. Nevertheless, you should consult with your health care provider before using ginkgo if you are taking thiazide diuretics.

Trazodone -- There has been a report of an adverse interaction between ginkgo and trazodone (Desyrel), an antidepressant medication that resulted in an elderly patient going into a coma.

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