Herbs & Supplements

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Uses

Increasing amounts of evidence show that herbal products made from ginkgo leaves may help to relieve a condition known as cerebral insufficiency, which is a decrease in the blood supply to the brain. Frequently associated with aging, cerebral insufficiency may cause confusion, dementia, hearing problems, and memory loss. Dementia is an increasing decline in thought processes caused by brain damage or disease. Chemicals in ginkgo leaves are known to thin the blood and they may also normalize muscle tone in blood vessel walls. Both of these effects may improve blood flow to the brain, thereby increasing the brain's oxygen supply and possibly relieving conditions associated with poor blood flow. Additionally, in laboratory studies, ginkgo leaf preparations seemed to prevent cell destruction caused by beta-amyloid proteins--chemicals thought to be involved in causing Alzheimer's disease. Ginkgo's possible effect on beta-amyloid proteins needs further study to determine its potential. At least one large, long-term study is underway to determine whether taking ginkgo can help to prevent or delay the start of dementia for healthy older adults. To date, no studies have found that supplementation with ginkgo leaf extract improves memory and thinking for individuals who do not have cerebral insufficiency or other conditions that affect thinking.

By increasing blood flow both in the small blood vessels at the back of the eyes and to the optic nerves, ginkgo leaf may also help to prevent or relieve some eye conditions. In animal and human studies, taking ginkgo leaf has restored at least part of color perception for individuals who have decreased color vision due to diabetes. Some evidence also suggests that ginkgo may also help to improve age-related macular degeneration (AMD), which is the destruction of the retinas' centers. AMD may destroy vision in the middle of the visual field and it may lead to blindness. In addition, ginkgo has shown a protective effect against some forms of glaucoma, a disease caused by increased pressure within the eyes.

Because chemicals in ginkgo leaves affect all blood vessels in the same ways, ginkgo may also increase general blood flow throughout the body. As one result, taking ginkgo leaf preparations may help to relieve conditions such as intermittent claudication, which is leg pain that occurs while walking. Intermittent claudication usually results from peripheral vascular disease--narrowing of blood vessels that may cause an inadequate blood flow to the arms and legs. Ginkgo leaves have also been studied for increasing the ability to tolerate cold temperatures. In a condition known as Raynaud's syndrome or Raynaud's phenomenon, spasms of the blood vessels in the ears, fingers, toes, and other outer parts of the body cause the blood vessels in these areas to narrow when they get cold or during times of emotional stress. The vessel-widening chemicals in the leaves of ginkgo may prevent these spasms and the pain they cause. Because ginkgo may increase blood flow to the penis, it has also been studied for the treatment of erectile dysfunction (ED), the inability for a man to have or maintain an erection. A few small human studies show that ginkgo may have limited effectiveness for treating ED, especially for men who have ED as a side effect from taking antidepressant medications. In animal studies, however, ginkgo may have had negative effects on male reproductive functions. All these possible uses of ginkgo leaf show promise, but much more study is needed before it can be recommended for any of them.

In Germany, herbal medicines are evaluated by the German Commission E (of the German Federal Institute for Drugs and Medical Devices), the German governmental agency that evaluates the safety and effectiveness of herbal products. Commission E has approved ginkgo leaf extract for treating symptoms of dementia, intermittent claudication, and related conditions. The United States does not have an agency comparable to the German Commission E.

In studies of laboratory animals, ginkgo leaf extract showed some ability to relieve inflammation and heal ulcers of the stomach or small intestine. Because it is an antioxidant, ginkgo leaf extract has also been tested in laboratory studies of human cancer cells. Antioxidants are believed to protect body cells from damage caused by oxidation, the chemical breakdown of foods into components the body can use. Oxidation also produces by-products known as oxygen free radicals, which may suppress immune function. Ginkgo leaf extract has also reduced chemically caused liver fibrosis in animal studies. Fibrosis is the formation of scar-like fibers. Because the non-functioning fibers crowd out active liver tissue, liver function decreases gradually as the amount of fibrous tissue increases. Chronic hepatitis and drinking large amounts of alcoholic beverages are the major causes of liver fibrosis. Damage from exposure to chemicals or certain drugs may also result in liver fibrosis.

Occasionally, the seeds of the ginkgo tree are used as medicine, more commonly in Asia than in Europe or North America, and only after they have been heated. Roasting the seeds destroys some of the potentially harmful chemicals they contain. These chemicals may cause seizures or death--especially in children. Toasted ginkgo seeds may limit the coughing reflex and also make mucus easier to eliminate from the lungs. Both these effects may make ginkgo seeds useful for controlling the coughing of asthma and other chronic respiratory conditions. Safer and more effective prescription and non-prescription drugs are available to treat coughing, however. The use of ginkgo seeds is not recommended. If ginkgo seeds are used, they should be used only occasionally and their use should be limited to no more than ten seeds per day for no more than a few days at a time.