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Ginkgo on the Brain

 

Ginkgo is well-known for its effect on memory and thinking (cognitive function). It may enhance cognitive performance in healthy older adults, in people with age-related cognitive decline, and in people with Alzheimer’s disease. Gingko is also used for other age-related disorders such as macular degeneration and depression in elderly people.

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.

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). Ginkgo's antioxidant action may extend to the brain and retina of the eye. Preliminary trials have suggested potential benefit for people with macular degeneration and diabetic retinopathy. 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. Ginkgo regulates the tone and elasticity of blood vessels, making circulation more efficient. Ginkgo biloba may help some men with erectile dysfunction (ED) by increasing blood flow to the penis. One double-blind trial found improvement in men taking 240 mg per day of a standardized Ginkgo biloba extract (GBE) for nine months. A preliminary trial, involving 30 men who were experiencing ED as a result of medication use (selective serotonin reuptake inhibitors and other medications), found that approximately 200 mg per day of GBE had a positive effect on sexual function in 76% of the men.

In a preliminary clinical trial, a standardized extract of Ginkgo biloba significantly reduced symptoms of vertigo in a group of elderly people with mild cognitive impairment. Participants were given 40 mg three times per day for one year. GBE has also been reported to significantly reduce vertigo of unknown cause in preliminary and double-blind trials. The amounts given were 120 mg and 160 mg per day, respectively, for three months.

Ginkgo biloba at a dose of 240 mg per day may also alleviate depression in depressed elderly people not responding to antidepressant drugs. It is unknown if ginkgo could alleviate depression in other age groups. A small, preliminary trial has shown that ginkgo can reduce sexual problems caused by antidepressants like fluoxetine (Prozac), bupropion (Wellbutrin), venlafaxine (Effexor), and nefazodone (Serzone) in men and women. Double-blind trials are now needed to determine whether ginkgo is truly effective for this purpose.

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. 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.

In a double-blind study, supplementation with a standardized extract of Ginkgo biloba in the amount of 40 mg three times a day for four weeks partially reversed visual field damage in people with one type of glaucoma (normal tension glaucoma).

Are there any side effects or interactions?
Excessive bleeding has been reported in a few individuals taking ginkgo, 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. Mild headaches lasting for a day or two and mild upset stomach have been reported in a small number of people using ginkgo.

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. These results suggest that the participants may have developed 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.

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.

 


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