Other common name(s): ginkgo biloba, maidenhair tree, EGb 761, yinhsing, yin xing ye
Scientific/medical name(s): Ginkgo biloba
Ginkgo is an extract of leaves from a ginkgo tree, one of the world's oldest surviving species of tree, which comes from China, Japan, and Korea. Ginkgo is used as a dietary supplement in the United States for a variety of conditions.
In some studies, Ginkgo has shown some benefit in the treatment of mild to moderate dementia. Other studies have shown that it can help improve blood circulation and flow to the brain. However, a large clinical trial found gingko did not preserve memory, prevent dementia, or reduce the risk of Alzheimer's disease in older people without dementia. A shorter clinical study found no advantage on memory tests for older adults who took gingko. Few side effects have been reported, but it has the potential to interfere with blood clotting, anesthesia, and some medicines. Available scientific evidence does not support claims that it is effective in preventing or treating cancer in humans.
How is it promoted for use?
Ginkgo is promoted as an aid to memory and concentration. It is believed to stimulate blood circulation and the flow of oxygen to the brain. Widely used in Europe, the extract has also become popular in the United States. Claims include improved memory and vision in the elderly and a slowing of the progression of Alzheimer's disease and dementia.
Ginkgo is sometimes promoted for tinnitus (ringing in the ears), sudden deafness, dizziness, altitude sickness, and intermittent claudication (cramp-like pain in the lower legs caused by poor circulation). In addition, ginkgo is promoted to treat a blood vessel disorder known as Raynaud's disease, in which the toes or fingers turn cool and pale when exposed to cold because of insufficient blood supply. European and Asian doctors have also used ginkgo in stroke patients to attempt to limit tissue damage to the brain.
Although ginkgo is not usually promoted as a cancer treatment, herbalists note that it contains some substances that may prove to have activity against cancer. Such compounds include flavonoids, which are thought to be anti-inflammatory, and proanthocyanidins, which are antioxidants. It also contains a compound called ginkgolide B, which may counteract a body chemical called platelet-activating factor (PAF) that is thought to promote tumor growth.
What does it involve?
Ginkgo leaf extract is on the Commission E (Germany's regulatory agency for herbs) list of approved herbs and can be taken by mouth in pill or liquid form. The average dose of ginkgo extract totals 120 to 240 milligrams (mg) per day, usually split into 2 to 3 doses. Proponents usually do not recommend the crude, dried leaf preparations because they believe this preparation does not contain enough of the active ingredients.
What is the history behind it?
Chinese herbalists have used the fruit of the ginkgo tree for about 4,000 years to help asthma, coughs, and allergic reactions. Cooked ginkgo seeds are also sometimes eaten after the pulp has been removed from the outside. In the past few decades, an extract of ginkgo leaves has been used in Western medicine, first in Europe and more recently in the United States, because it is supposed to help memory, brain function, and blood circulation.
What is the evidence?
The possible effects of ginkgo leaf extract in preventing or treating cancer have not been well studied. Some small studies done in Asia have suggested that ginkgo extract may affect cancer cells in culture dishes and laboratory animals. No studies have been done to show it can prevent or treat cancer in humans. A few small studies have looked at adding ginkgo to other treatments in cancer patients, but the results have not been conclusive. More research is needed in this area.
Ginkgo leaf extract appears to improve blood flow to the brain. Some early studies found ginkgo extract seemed to improve memory. A few randomized, controlled studies have found that certain ginkgo extracts can improve brain and social function in patients with mild to moderate dementia due to Alzheimer's disease or problems with blood flow in the brain. But reviews of gingko studies show that study outcomes are not consistent or reliable in proving that gingko can help people with dementia or other brain impairment.
To look at people with more normal brain function, the Ginkgo Evaluation of Memory (GEM) clinical trial followed over 3000 US residents aged 72 to 96 years for more than 6 years. These were volunteers who lived in their communities and did not have dementia or Alzheimer's disease when they started the clinical trial. Half were given gingko and half a sham pill that looked like gingko. When the study ended in 2009, there was no difference in memory, language, planning, and other brain functions between those who got gingko and those who got placebos. Also, there was no significant difference in the numbers from gingko or placebo groups diagnosed with dementia or Alzheimer's disease during the study. Along those same lines, a randomized, double-blind 6-week clinical study compared gingko to placebo in 200 normal people over age 60. The study tested memory, learning, and concentration. It found no difference between those taking gingko and those taking placebo.
A 2009 review of 14 studies found that the evidence for gingko helping claudication (cramps due to poor blood supply) was weak. A 2004 review of studies concluded that there was not enough evidence to support claims that ginkgo can help tinnitus (ringing in the ears). A few studies have found ginkgo leaf extract may have small to modest benefits in patients with sudden hearing loss. In all of these cases, larger, well designed studies are needed.
Are there any possible problems or complications?
This product is sold as a dietary supplement in the United States. Unlike companies that produce drugs (which must be tested before being sold), the companies that make supplements are not required to prove to the Food and Drug Administration that their supplements are safe or effective, as long as they don't claim the supplements can prevent, treat, or cure any specific disease.
Some such products may not contain the amount of the herb or substance that is on the label, and some may include other substances (contaminants). Actual amounts per dose may vary between brands or even between different batches of the same brand. In 2007, the FDA wrote new rules to improve the quality of manufacturing for dietary supplements and the proper listing of supplement ingredients. But these rules do not address the safety of the ingredients or their effects on health.
Most such supplements have not been tested to find out if they interact with medicines, foods, or other herbs and supplements. Even though some reports of interactions and harmful effects may be published, full studies of interactions and effects are not often available. Because of these limitations, any information on ill effects and interactions below should be considered incomplete.
Ginkgo leaf extract is generally considered safe. Some possible side effects include headache, mild stomach upset, and diarrhea. Because it may block the action of platelets (which help make the blood clot), ginkgo is not recommended for people using aspirin, other non-steroidal anti-inflammatory drugs (such as ibuprofen), or blood-thinning medications such as warfarin (Coumadin). Doctors often advise stopping the use of ginkgo products several days before surgery. People with seizure disorders should not use ginkgo because it may reduce the effects of anti-seizure drugs. Potential interactions between ginkgo and other drugs and herbs should be considered. Some combinations may be dangerous. Always tell your doctor and pharmacist about any herbs you are taking.
Allergic reactions to gingko have been reported, including severe skin reactions with blistering. People who react to poison ivy, mango, cashews, and sumac may be more likely to react to ginkgo. Products that contain gingkolic acid may cause more problems, including allergic reactions.
Uncooked ginkgo fruit or seed can cause more serious problems, including vomiting, seizures, and loss of consciousness. The seed contains a toxin that is reported to be inactivated by cooking. Poisoning from eating the seeds has been reported in adults and children, sometimes resulting in death. The uncooked fruit and seed are also more likely to cause allergic rashes and intestinal irritation than the leaf extract.
This herb has not been studied in women who are pregnant or breast-feeding. Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.
More information from your American Cancer Society
The following information on complementary and alternative therapies may also be helpful to you. These materials may be found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-ACS-2345).
The ACS Operational Statement on Complementary and Alternative Methods of Cancer Management
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Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.
Last Revised: 05/13/2010