Ginkgo has been termed “a biological super-tree,” because individual trees may live for over 1,000 years and the species itself (Ginkgo biloba) has survived almost unchanged for over 150 million years. The vast majority of the ginkgo products on the market today are standardized extracts made from the tree’s distinctive fan-shaped leaves.
Benefits and uses:
The Chinese have used ginkgo for thousands of years to treat various conditions, including memory loss, asthma, allergies, and coughs. It is now among the most widely recommended herbal medicines in Europe and the U.S., where many people take it regularly as an energizer to improve mood and alertness, as a “smart drug” to stimulate brain function and boost memory, and as an antioxidant to slow the effects of aging and prevent degenerative diseases. Researchers say that ginkgo stimulates circulation in the brain, ears, and other parts of the body and thus may help prevent hearing loss, stroke, Alzheimer’s disease, and depression. Studies indicate it has potential use in the treatment of impotence, varicose veins, and other circulatory conditions. Ginkgo may also help prevent diabetes, macular degeneration, and multiple sclerosis.
Do scientists know how it works?
Plant scientists believe that the most active constituents of ginkgo are certain flavonoid compounds known as “flavon glycosides” or “ginkgoheterosides,” and certain complex terpene compounds, such as bilobalide and one or more of the ginkgolides. Many of ginkgo’s positive effects are tied to its potency as an antioxidant, a protector of nervous system cells, and regulator of blood platelet stickiness.
Two well-designed studies, including a multicenter study published in the Journal of the American Medical Association, documented beneficial effects from using ginkgo extracts in the treatment of Alzheimer’s disease. Another study found that ginkgo’s ability to protect the nervous system from damage due to conditions such as hypoxia and seizure activity may be due to both the ginkgolides and the herb’s free radical scavenging flavonoids. Also, the mechanism for ginkgo’s stress- and anxiety-reducing actions may be related to an inhibitory effect on monoamine oxidase (MAO), an enzyme found in nerve cells that can inactivate neurotransmitters and thus lower mood.
No long-term toxicity and few side effects have ever been associated with ginkgo. Newcomers to the herb, however, who take single doses in excess of 300 mg or so may experience mild headaches or dizziness. Some ginkgo users may also experience minor stomach or gastric upset. There are no known contraindications to the use of ginkgo by pregnant or lactating women. People who are taking daily aspirin to thin the blood or prescription anticoagulants such as warfarin (Coumadin) should avoid ginkgo to reduce the risk of excessive bleeding.
What types of ginkgo products are available?
Among the most popular ginkgo products are encapsulated extracts standardized to 24 percent of flavon glycosides and 6 percent terpene lactones. Ginkgo also comes in soft gels, tablets, liquids, and the powdered whole herb. Ginkgo is usually a prominent component in brain and memory, and mind and mood, formulas.
LeBars, P.L., et al., “A placebo-controlled, double-blind, randomized trial of an extract of Ginkgo biloba for dementia,” JAMA (1997), 278:1327–32Kanowski, S., et al., “Proof of efficacy of the Ginkgo biloba special extract EGb 761 in outpatients suffering from mild to moderate primary degenerative dementia of the Alzheimer’s type or multi-infarct dementia,” Phytomedicine (1997), 4/1:3–13Smith, P.F., et al., “The neuroprotective properties of the Ginkgo biloba leaf: a review of the possible relationship to platelet-activating factor (PAF),” J Ethnopharmacol (1996), 50(3):131–39White, H.L., et al., “Extracts of Ginkgo biloba leaves inhibit monoamine oxidase,” Life Sciences (1996), 58:1315–21