Ginkgo, the world's oldest living species of tree, 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. Research has demonstrated that ginkgo also helps with the following health concerns: 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, and vitiligo.
The medical benefits of Ginkgo biloba extract (GBE) 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 GBE's antioxidant activity and may mildly inhibit platelet aggregation (stickiness). These two actions may help GBE prevent circulatory diseases, such as atherosclerosis, and support the brain and central nervous system. In addition to the cardiovascular system, GBE's antioxidant action may also extend to the brain and retina of the eye and some constituents are associated with increasing circulation to the brain and other parts of the body and may exert a protective action on nerve cells. GBE regulates the tone and elasticity of blood vessels, making circulation more efficient.
How much is usually taken?
Most clinical trials have used between 120 and 240 mg of GBE (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. GBE 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 GBE, 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 GBE. Mild headaches lasting for a day or two and mild upset stomach have been reported in a small number of people using GBE.
Ginkgo leaves are known to contain a group of potentially toxic constituents known as alkylphenols. The ginkgo extracts known as EGb 761 and LI 1370 have been shown to conform to the safety limits for these constituents (less that 5 ppm), as set forth by the German Commission E. Other forms of ginkgo may contain higher concentrations of alkylphenols.
People should seek an accurate medical diagnosis prior to self-prescribing GBE. This is especially important for the elderly, whose circulatory conditions can involve serious disease, and for people scheduled for surgery, as GBE may affect bleeding time.
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