Herbs & Supplements

Should I take it?

Ginkgo is thought to be the oldest tree species on earth: with fossilized ginkgo dated at over 220 million years old. Furthermore, historical records kept in China may place the age of individual, still-living ginkgo trees at 1,000 years or older. Under favorable growing conditions, ginkgo trees may reach over 100 feet in height. However, the ginkgos most familiar to residents of the United States are generally small trees. They are often planted in cities because they can survive in harsh weather and they resist damage from diseases, insects, and pollution.

Ginkgos are easily recognized by their distinctive fan-shaped leaves--light green in summer, but turning to a brilliant yellow in the autumn. For use in medicine, ginkgo leaves are picked while they are green, dried, and extracted. Extracts are concentrated liquid preparations usually made by soaking chopped or mashed plant parts in a liquid such as alcohol or acetone, and then straining out the solid parts. The resulting liquid may then be dried and placed in capsules or made into tablets.

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 (GLE) for treating symptoms of dementia, intermittent claudication, and related conditions. The United States does not have an agency comparable to the German Commission E.

Female ginkgo trees bear foul-smelling, tannish-colored fruits about the size and shape of large cherries. The pulp of ginkgo fruits contains chemicals that cause irritation when they come in contact with human skin. Although the fruits are not eaten as food, the large seed contained in each fruit may be used in medicine, but only after being heated to remove some of the potentially harmful chemicals. Ginkgo seeds resemble peeled almonds in color, shape, and size. Occasionally, ginkgo seeds have been used in combination herbal preparations to treat chronic cough and congestion. Sometimes, they are used in small quantities as a ceremonial food for special occasions in oriental counties. Taking ginkgo seeds by mouth is discouraged strongly due to the possibility that chemicals contained in the seeds may cause seizures or even death.

Dosage and Administration

Ginkgo leaf is most commonly available as an extract, which is made by soaking dried, green ginkgo leaves in a liquid such as acetone, straining out the solid particles, and then evaporating the acetone to produce a concentrate. Often abbreviated as GLE, ginkgo leaf extract may be used as a liquid or it may be dried and made into capsules or tablets. Frequently, ginkgo leaf preparations are standardized to contain between 22% and 27% of chemicals known as ginkgo flavonol glycosides and between 5% and 7% of another group of chemicals known as terpene lactones. Standardization by the manufacturer should assure the same amount of active ingredient in every batch of the commercial preparation. Standardization of herbal products is not required by the U.S. Food and Drug Administration (FDA), so not every product sold in this country will contain the same amounts of active ingredients.

Daily amounts of ginkgo are usually divided into two doses or three doses. For treating dementia and related symptoms such as memory loss, recommended amounts of GLE range from 120 mg to 240 mg per day. The suggested daily amount for intermittent claudication is 120 mg to 160 mg. Higher oral doses have not shown any additional value and GLE may take between 6 weeks and 8 weeks to reach full effectiveness.

Taking ginkgo seeds is not advised. Individuals who decide to use ginkgo seeds should never try to harvest and roast the seeds themselves. Although no recommendations for dosing amounts or intervals of ginkgo seeds are available in scientific literature, most sources recommend no more than ten commercially prepared seeds per day. Additionally, taking ginkgo seed products should be very limited--no more than a few days at any one time and very few times a year. If ginkgo seeds are used, a reputable commercial preparation should be purchased and the dosing recommendations on the package should be followed exactly. Most often, ginkgo seed is included in combination herbal products.

Summary

The leaves of the ginkgo tree contain chemicals that decrease the thickness of blood and increase the size of blood vessels. The resulting increased blood flow improves oxygen levels which may relieve conditions such as memory loss, intermittent claudication, macular degeneration, and glaucoma. Roasted ginkgo seeds may sometimes be used to treat chronic respiratory conditions such as asthma.

Risks

Due to its ability to inhibit blood clotting, ginkgo should be avoided by individuals with bleeding disorders. Since it may trigger seizures, ginkgo should not be taken by individuals with epilepsy or other conditions that may result in seizures. And because ginkgo may affect blood sugar levels, individuals with diabetes should not take it.

Side Effects

Either ginkgo leaf or--more likely--ginkgo seed may trigger seizures.

Taking ginkgo leaf preparations may cause unexpected bleeding into the eyes or under the skin. Mild headache, muscle weakness, or stomach upset may also be attributed to using ginkgo leaf. Consuming any amount of fresh ginkgo seeds or more than about ten roasted seeds at one time has resulted in breathing difficulty, unconsciousness, or death. Eating or touching ginkgo fruits may be associated with skin irritation, redness, or swelling.

Interactions

Ginkgo leaf extract (GLE) may increase the effects of drugs and herbals that reduce blood clotting. It may interfere with insulin and oral drugs or herbs that affect blood sugar.

Taking either ginkgo leaf or ginkgo seed may decrease the effects of anticonvulsant drugs. They may also increase the chance of a seizure if they are taken with several different types of prescription and non-prescription drugs or herbal products that may also make seizures more likely to occur.

Last Revised July 18, 2008