Ginkgo biloba is an herbal dietary supplement made from the leaves of the tree Ginkgo biloba.
Ginkgo biloba, sometimes called bai guo, has been used in traditional Chinese medicine (TCM) for about 5,000 years to treat memory loss as well as mood, nerve, circulatory, and many other health problems. Ginkgo biloba often is combined with ginseng to boost memory, improve the quality of life, and increase a sense of well-being. The effectiveness of some TCM uses of ginkgo, such as relieving pain caused by clogged arteries in the leg (claudication), treating Alzheimer's disease, and improving blood flow to the brain have been evaluated in well-designed studies, and are generally accepted by practitioners of conventional medicine. Many other TCM uses of ginkgo biloba are currently being investigated.
The fan-shaped leaves of the ginkgo are used for medicinal purposes. About twenty different compounds have been identified in ginkgo leaves, but the medically active ingredients appear to be flavonoids and terpenoids. Flavonoids are antioxidants that may help lower the level of free radicals in the body. Terpenoids are thought to protect nerves from damage, reduce inflammation, and decrease blood clotting.
In the United States, Ginkgo biloba is cultivated, and the leaves are harvested and dried, and then often used to make a standardized extract that contains 24%–25% flavonoids and 6% terpenoids. U.S. law does not require the standardization of dietary supplements, so consumers should read all labels carefully. Ginkgo biloba is often sold as capsules and tablets. Dry and liquid ginkgo extract is added to other herbal remedies as well as teas, energy or health bars, and similar products. An injectable form of ginkgo biloba extract that was available in Europe has been withdrawn from the market because of adverse side effects. Most well-designed studies have been done using a total of 80–240 mg (.0028–.0085 oz.) of 50:1 standardized extract divided into two or three doses daily and taken by mouth.
Ginkgo biloba is one of the top selling herbal remedies in the United States and is even more popular in Europe. Under the 1994 Dietary Supplement Health and Education Act (DSHEA), the sale of ginkgo biloba is regulated by the U.S. Food and Drug Administration (FDA) as a dietary supplement. At the time the act was passed, legislators felt, because many dietary supplements such as ginkgo biloba come from natural sources and have been used for hundreds of years by practitioners of complementary and alternative medicine (CAM), supplements did not need to be regulated as rigorously as prescription and over-the-counter drugs used in conventional medicine.
The DSHEA regulates ginkgo biloba in the same way that food is regulated. Like food manufacturers, manufacturers of herbal products containing ginkgo biloba do not have to prove that they are either safe or effective before they can be sold to the public. This differs from conventional pharmaceutical drugs, which must undergo extensive human testing to prove their safety and effectiveness before they can be marketed. Also, unlike conventional drugs, the label for a dietary supplement such as ginkgo biloba does not have to contain any statements about possible side effects. All herbal supplements sold in the United States must show the scientific name of the herb on the label.
Ginkgo biloba is thought to be one of the most promising traditional herbs investigated by Western medicine. The National Center for Complementary and Alternative Medicine (NCCAM), a government organization within the National Institutes of Health, has sponsored clinical trials to determine safety and effectiveness of ginkgo biloba as a treatment for more than a dozen diseases and disorders, including Alzheimer's disease and other cognitive function disorders.
Some health claims for ginkgo biloba have already been evaluated in large, well-controlled studies that satisfy the proof of safety and effectiveness demanded by conventional medicine. A review of studies published between 1970 and 2017 concluded that botanical supplements, including ginkgo, show real promise as therapies to delay the onset and progression of age-related cognitive decline. There is good evidence that ginkgo biloba can cause short-term improvement in mental function in people with Alzheimer's disease. In a well-designed study, ginkgo biloba was as effective as the prescription drug donepezil (Aricept) in slowing the development of dementia in people with mild to moderate Alzheimer's. Ginkgo biloba has also been shown to be effective in improving blood flow to the brain and in treating certain other dementias.
Many healthy younger people take gingko biloba supplements to improve their memories, but the effect of ginkgo biloba on memory in healthy young adults is less well established and may not exist at all. A meta-analysis published in 2012 found no effect of ginkgo on cognitive function in healthy people. Other studies have also found no effect.
Several health claims for ginkgo biloba center on treating disorders of the eye, including glaucoma, age-related macular degeneration, and type 2 diabetes– related retinopathy. Ginkgo appears to increase blood flow to the eye, but additional studies need to be done to evaluate its effectiveness in helping to treat these disorders.
The terpenoids in ginkgo biloba are thought to help prevent nerve damage. Because of this, ginkgo has been suggested as a treatment for tinnitus (ringing of the ears), multiple sclerosis, cochlear deafness, and Huntington's disease. A 2017 paper analyzing various studies using ginkgo to treat tinnitus found that results were mixed, with some studies reporting that ginkgo was an effective treatment and others finding no effect.
Some researchers have suggested that ginkgo biloba is useful in treating depression, seasonal affective disorder, premenstrual syndrome, altitude sickness, vertigo (dizziness), premenstrual syndrome (PMS), gastric cancer, side effects of anticancer drugs, and pulmonary interstitial fibrosis, as well as generally improving quality of life and sense of well-being. Further studies need to be carried out, however, to support these claims.
Eating ginkgo fruits is not safe. Many cities have planted ginkgo trees as ornamental plants, and the female trees produce fruit every year. The fruits look like small plums and, though they smell terrible to humans, they may appear appetizing. In fact, ginkgo fruits are toxic to humans, and contact between skin and ginkgo fruit can cause skin rashes. People do eat ginkgo seeds as a delicacy. Ginkgo biloba seeds contain toxins that can cause vomiting, seizures, loss of consciousness, and death, especially in young children or if eaten in large quantities, so anyone interested in eating ginkgo seeds should research the topic first.
Extracts of the leaf of Ginkgo biloba are generally safe and cause few side effects when taken at recommended doses for up to six months. People who are planning to have surgery should stop taking ginkgo biloba at least two days before their operation because of the risk of increased bleeding. The safety of ginkgo biloba in children and pregnant and breastfeeding women is still being studied.
Ginkgo biloba has blood-thinning properties and is likely to increase the blood-thinning and anticoagulant effects of medicines such as warfarin (Coumadin), clopidogrel (Plavix), aspirin, and nonsteroidal anti-inflammatory drugs (e.g., Advil, Motrin). Individuals taking these drugs should not begin taking ginkgo biloba without consulting their healthcare provider.
Ginkgo biloba may also interact with monoamine-oxidase inhibitors (MAOIs) used to treat certain kinds of depression and mental illness. Examples of MAOIs include isocarboxazid (Marplan), phenelzine (Nardil), and tranylcypromine (Parnate). Individuals taking MAOIs along with ginkgo biloba may experience increased effects from the MAOI.
Some reports suggest that ginkgo biloba lowers blood sugar levels. Individuals who are taking insulin or other medications that also lower blood sugar, and those with type 2 diabetes, should consult their healthcare provider before starting to take ginkgo biloba.
Parents should be aware that the safe dose of many herbal supplements has not been established for children. Accidental overdose may occur if children are given adult herbal supplements.
See also Antioxidants ; Asian diet ; Dietary supplements ; Ginseng .
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Office of Dietary Supplements, National Institutes of Health, 6100 Executive Blvd., Rm. 3B01, MSC 7517, Bethesda, MD, 20892-7517, (301) 435-2920, Fax: (301) 480-1845, email@example.com, https://ods.od.nih.gov .
Tish Davidson, AM
Revised by Amy Hackney Blackwell, PhD