Ginkgo (Ginkgo biloba) is one of the oldest living tree species and its leaves are among the most extensively studied herbs in use today. In Europe and the United States, ginkgo supplements are among the best-selling herbal medications. It consistently ranks as a top medicine prescribed in France and Germany.
Ginkgo has been used in traditional medicine to treat blood disorders and enhance memory. Scientific studies throughout the years have found evidence that supports these claims. Although not all studies agree, ginkgo may be help treat dementia (including Alzheimer's disease) and intermittent claudication, or poor circulation in the legs. It also shows promise for enhancing memory in older adults. Laboratory studies have shown that ginkgo improves blood circulation by dilating blood vessels and reducing the stickiness of blood platelets.
Ginkgo leaves contain two types of chemicals (flavonoids and terpenoids) believed to have potent antioxidant properties. Antioxidants are substances that scavenge free radicals -- compounds in the body that damage cell membranes, tamper with DNA, and even cause cell death. Free radicals are believed to contribute to health problems including heart disease and cancer as well as Alzheimer's disease and other forms of dementia. Antioxidants such as those found in ginkgo can help neutralize free radicals and may reduce or even help prevent some of the damage they cause.
Ginkgo biloba is the oldest living tree species. A single tree can live as long as 1,000 years and grow to a height of 120 feet. It has short branches with fan-shaped leaves and inedible fruits that produce a strong odor. The fruit contains an inner seed, and there has been a report of a human poisoning from ingesting the seed. Ginkgos are tough, hardy trees and are sometimes planted along urban streets in the United States.
Although Chinese herbal medicine has used both the ginkgo leaf and seed for thousands of years, modern research has focused on the standardized Ginkgo biloba extract (GBE), which is made from the dried green leaves. This standardized extract is highly concentrated and seems to be more effective in treating health problems (particularly circulatory ailments) than the non-standardized leaf alone.
More than 40 components from the ginkgo tree have been identified, but only two are believed to act as medicine: flavonoids and terpenoids. Flavonoids are plant-based antioxidants. Laboratory and animal studies have shown that flavonoids protect the nerves, heart muscle, blood vessels, and retina from damage. Terpenoids (such as ginkgolides) improve blood flow by dilating blood vessels and reducing the stickiness of platelets.
Based on studies conducted in laboratories, animals, and humans, ginkgo is used for the following:
Dementia and Alzheimer's disease
Ginkgo is widely used in Europe for treating dementia. It was first used because it improves blood flow to the brain. Now further study suggests it may directly protect nerve cells that are damaged in Alzheimer's disease. A number of studies have found that ginkgo has a positive effect on memory and thinking in people with Alzheimer's or vascular dementia.
Clinical studies suggest that ginkgo may have the following benefits for people with Alzheimer's disease:
Several studies have found that ginkgo may work as well as prescription Alzheimer's medications in delaying the symptoms of dementia.
However, one of the longest and best-designed studies found ginkgo was no better than placebo in reducing Alzheimer's symptoms. In a 2008 study, 176 people in the United Kingdom with Alzheimer's took either ginkgo or placebo for 6 months. At the end of the study there was no difference in mental function or quality of life between the groups.
Ginkgo is sometimes suggested to prevent Alzheimer's and dementia, as well, and some studies have suggested it might be helpful. But in 2008, a well-designed study (the GEM study) with more than 3,000 elderly participants found the ginkgo was no better than placebo in preventing dementia or Alzheimer's.
Because ginkgo improves blood flow, it has been studied in people with intermittent claudication, or pain caused by reduced blood flow to the legs. People with intermittent claudication have a hard time walking without feeling extreme pain. An analysis of eight studies revealed that people taking ginkgo tend to walk about 34 meters farther than those taking placebo. In fact, ginkgo has been shown to be as effective as a prescription medication in improving pain-free walking distance. However, regular walking exercises work better than ginkgo in improving walking distance.
One small study found that people with glaucoma who took 120 mg of ginkgo daily for 8 weeks had improvements in their vision.
Ginkgo is widely touted as a "brain herb." It has been studied to see whether it can improve memory in people with dementia, and some studies found it did help. It's not as clear whether ginkgo helps memory in healthy people who have normal, age-related memory loss. Some studies have found slight benefits, while other studies have found no effect on memory. The most effective dose seems to be 240 mg per day. Ginkgo is commonly added to nutrition bars, soft drinks, and fruit smoothies to boost memory and enhance mental performance, although it's unlikely that such small amounts of ginkgo would work.
The flavonoids found in ginkgo may help stop or lessen some retinal problems -- problems with the back part of the eye. Macular degeneration, often called age-related macular degeneration or ARMD, is an eye disease that affects the retina. It is a progressive, degenerative eye disease that tends to affect older adults and is the number one cause of blindness in the United States. Some studies suggest that ginkgo may help preserve vision in those with ARMD.
Nerve damage and certain blood vessel disorders can lead to tinnitus -- ringing, hissing, or other sound in the ears or head. Because ginkgo improves circulation, it has been studied to see whether it can treat tinnitus. A few poorly designed studies found it might reduce the loudness of the sound. However, a well-designed study including 1,121 people with tinnitus found that ginkgo was no better than placebo in relieving tinnitus symptoms. In general, tinnitus is a very difficult problem to treat.
Raynaud' s Phenomenon
One well-designed study found that people with Raynaud' s phenomenon who took ginkgo over a 10-week period had fewer symptoms than those who took placebo. More studies are needed.
Ginkgo is not generally used in children.
Initial results often take 4 - 6 weeks, but should grow stronger beyond that period.
Memory impairment and cardiovascular function: Generally, 120 mg daily in divided doses, standardized to contain 24 - 32% flavone glycosides (flavonoids or heterosides) and 6 - 12% triterpene lactones (terpenoids). If more serious dementia or Alzheimer's disease is present, up to 240 mg daily, in 2 or 3 divided doses, may be necessary.
Intermittent claudication: 120 - 240 mg per day
The use of herbs is a time-honored approach to strengthening the body and treating disease. Herbs, however, contain components that can trigger side effects and interact with other herbs, supplements, or medications. For these reasons, herbs should be taken with care, under the supervision of a health care provider qualified in the field of botanical medicine.
Ginkgo usually has few side effects. In a few cases, stomach upset, headaches, skin reactions, and dizziness were reported.
There have been a number of reports of internal bleeding in people who take ginkgo. However, it' s not clear whether the bleeding was due to ginkgo or some other reasons, such as a combination of ginkgo and blood-thinning drugs. Researchers aren' t sure, because different studies have found different results. You should ask your doctor before taking ginkgo if you also take blood-thinning drugs.
If you take ginkgo, you should stop taking it at least 36 hours before surgery or dental procedures due to the risk of bleeding. Tell your doctor or dentist that you take ginkgo.
People who have epilepsy should not take ginkgo, because there is concern that it might cause seizures.
Pregnant and breastfeeding women should not take ginkgo.
People who have diabetes should ask their doctor before taking ginkgo.
Do not eat Ginkgo biloba fruit or seed.
Ginkgo may interact with some prescription and non-prescription medications. If you are taking any of the following medications, you should not use ginkgo without first talking to your health care provider:
Medications metabolized by the liver -- Ginkgo can interact with some medications that are processed through the liver. If you take any prescription medications, ask your doctor before taking ginkgo.
Seizure medications (anticonvulsants) -- High doses of ginkgo could make drugs to control seizures, such as carbamazepine (Tegretol) or valproic acid (Depakote), less effective.
Antidepressants -- Taking ginkgo along with a kind of antidepressant called selective serotonin reuptake inhibitors (SSRIs) may increase the risk of serotonin syndrome, a potentially fatal condition. Ginkgo may strengthen both the good and bad effects of antidepressant medications known as MAOIs, such as phenelzine (Nardil). SSRIs include:
Medications for high blood pressure -- Ginkgo may lower blood pressure, so taking it with blood pressure medications may cause blood pressure to drop too low. There has been a report of an interaction between ginkgo and nifedipine (Procardia), a calcium channel blocker used for blood pressure and arrhythmias.
Blood-thinning medications -- Ginkgo may raise the risk of bleeding, especially if you take blood-thinners such as warfarin (Coumadin), clopidogrel (Plavix), and aspirin.
Ibuprofen (Advil, Motrin) -- Like ginkgo, the nonsteroidal anti-inflammatory drug (NSAID) ibuprofen also raises the risk of bleeding. There has been bleeding in the brain reported when using a ginkgo product and ibuprofen.
Medications to lower blood sugar -- Ginkgo may raise or lower insulin levels and blood sugar levels. If you have diabetes, you should not use ginkgo without first talking to your doctor.
Cylosporine -- Ginkgo biloba may help protect the cells of the body during treatment with the drug cyclosporine, which suppresses the immune system.
Thiazide diuretics (water pills) -- There is one report of a person who took a thiazide diuretic and ginkgo developing high blood pressure. If you take thiazide diuretics, ask your doctor before taking ginkgo.
Trazodone -- There is one report of an elderly Alzheimer's patient going into a coma after taking ginkgo and trazodone (Desyrel), an antidepressant medication.
Fossil tree; Kew tree; Maiden hair tree
Aruna D, Naidu MU.Pharmacodynamic interaction studies of Ginkgo biloba with cilostazol and clopidogrel in healthy human subjects. Br J Clin Pharmacol. 2006 Sep 29; [Epub ahead of print].
Ashton, A. K., Ahrens, K., Gupta, S., and Masand, P. S. Antidepressant-induced sexual dysfunction and Ginkgo Biloba. Am J Psychiatry. 2000;157(5):836-837.
Birks J, Grimley Evans J. Ginkgo biloba for cognitive impairment and dementia. Cochrane Database Syst Rev. 2009 Jan 21;(1):CD003120. Review.
Bridi, R., Crossetti, F. P., Steffen, V. M., and Henriques, A. T. The antioxidant activity of standardized extract of Ginkgo biloba (EGb 761) in rats. Phytother Res 2001;15(5):449-451.
Cheuvront, S. N. and Carter, R., III. Ginkgo and memory. JAMA. 2-5-2003;289(5):547-548.
Christen Y. Oxidative stress and Alzheimer's disease. Am J Clin Nutr. 2000;71(suppl):621S-629S.
Choi WS, Choi CJ, Kim KS, Lee JH, Song CH, Chung JH, et al. To compare the efficacy and safety of nifedipine sustained release with Ginkgo biloba extract to treat patients with primary Raynaud's phenomenon in South Korea; Korean Raynaud study (KOARA study). Clin Rheumatol. 2009 Jan 22. [Epub ahead of print]
Cieza, A., Maier, P., and Poppel, E. Effects of Ginkgo biloba on mental functioning in healthy volunteers. Arch Med Res. 2003;34(5):373-381.
Davydov L and Stirling AL. Stevens-Johnson syndrome with Ginkgo biloba. J Herbal Pharmacother. 2001;1(3):65-69.
DeKosky ST, Williamson JD, Fitzpatrick AL, Kronmal RA, Ives DG, Saxton JA, et al; Ginkgo Evaluation of Memory (GEM) Study Investigators. Ginkgo biloba for prevention of dementia: a randomized controlled trial. JAMA. 2008 Nov 19;300(19):2253-62. Erratum in: JAMA. 2008 Dec 17;300(23):2730.
Diamond BJ, Shiflett SC, Feiwel N, et al. Ginkgo biloba extract: mechanisms and clinical indications. Arch Phys Med Rehabil. 2000;81:669-678.
Drew S, Davies E. Effectiveness of Ginkgo biloba in treating tinnitus: double blind, placebo controlled trial. BMJ. 2001;322(7278):73.
Engelsen, J., Nielsen, J. D., and Hansen, K. F. [Effect of Coenzyme Q10 and Ginkgo biloba on warfarin dosage in patients on long-term warfarin treatment. A randomized, double-blind, placebo-controlled cross-over trial]. Ugeskr.Laeger. 4-28-2003;165(18):1868-1871.
Ernst E. The risk-benefit profile of commonly used herbal therapies: ginkgo, St. John's wort, ginseng, echinacea, saw palmetto, and kava. Ann Intern Med. 2002;136:42-53.
Hartley, D. E., Elsabagh, S., and File, S. E. Gincosan (a combination of Ginkgo biloba and Panax ginseng): the effects on mood and cognition of 6 and 12 weeks' treatment in post-menopausal women. Nutr Neurosci. 2004;7(5-6):325-333.
Hilton, M. and Stuart, E. Ginkgo biloba for tinnitus. Cochrane Database Syst Rev. 2004;(2):CD003852.
Horsch, S. and Walther, C. Ginkgo biloba special extract EGb 761 in the treatment of peripheral arterial occlusive disease (PAOD)--a review based on randomized, controlled studies. Int.J Clin Pharmacol Ther. 2004;42(2):63-72.
Huang, S. Y., Jeng, C., Kao, S. C., Yu, J. J., and Liu, D. Z. Improved haemorrheological properties by Ginkgo biloba extract (Egb 761) in type 2 diabetes mellitus complicated with retinopathy. Clin.Nutr. 2004;23(4):615-621.
Johnson SK, Diamond BJ, Rausch S, Kaufman M, Shiflett SC, Graves L. The effect of Ginkgo biloba on functional measures in multiple sclerosis: a pilot randomized controlled trial. Explore (NY). 2006;2(1):19-24.
Kampman, K., Majewska, M. D., Tourian, K., et al., A pilot trial of piracetam and ginkgo biloba for the treatment of cocaine dependence. Addict Behav. 2003;28(3):437-448.
Kenney C, Norman M, Jacobson M, and et al. A double-blind, placebo-controlled, modified crossover pilot study of the effects of Ginkgo biloba on cognitive and functional abilities in multiple sclerosis. American Academy of Neurology 54th Annual Meeting. April 13-20 2002;P06.081.
Kim YS, Pyo MK, Park KM, et al. Antiplatelet and antithrombotic effects of a combination of ticlopidine and Ginkgo biloba ext (EGb 761). Thromb Res. 1998;91:33-38.
Kohler, S., Funk, P., and Kieser, M. Influence of a 7-day treatment with Ginkgo biloba special extract EGb 761 on bleeding time and coagulation: a randomized, placebo-controlled, double-blind study in healthy volunteers. Blood Coagul.Fibrinolysis. 2004;15(4):303-309.
Le Bars PL, Kieser M, Itil KZ. A 26-week analysis of a double-blind, placebo-controlled trial of the Ginkgo biloba extract EGb761 in dementia. Dement Geriatr Cogn Disord. 2000;11:230-237.
Mantle D, Pickering AT, Perry AK. Medicinal plant extracts for the treatment of dementia: a review of their pharmacology, efficacy and tolerability. CNS Drugs. 2000;13:201-213.
Mauro, V. F., Mauro, L. S., Kleshinski, J. F., Khuder, S. A., Wang, Y., and Erhardt, P. W. Impact of ginkgo biloba on the pharmacokinetics of digoxin. Am.J Ther 2003;10(4):247-251.
May BH, Lit M, Xue CC, Yang AW, Zhang AL, Owens MD, et al. Herbal medicine for dementia: a systematic review. Phytother Res. 2008 Dec 11;23(4):447-459.
May BH, Yang AW, Zhang AL, Owens MD, Bennett L, Head R, et al. Chinese herbal medicine for Mild Cognitive Impairment and Age Associated Memory Impairment: a review of randomised controlled trials. Biogerontology. 2009 Apr;10(2):109-23. Epub 2008 Aug 21.
Mazza M, Capuano A, Bria P, Mazza S. Ginkgo biloba and donepezil: a comparison in the treatment of Alzheimer's dementia in a randomized placebo-controlled double-blind study. Eur J Neurol. 2006;13(9):981-5.
McCarney R, Fisher P, Iliffe S, van Haselen R, Griffin M, van der Meulen J, Warner J. Ginkgo biloba for mild to moderate dementia in a community setting: a pragmatic, randomised, parallel-group, double-blind, placebo-controlled trial. Int J Geriatr Psychiatry. 2008 Dec;23(12):1222-30.
Moher D, Pham B, Ausejo M, Saenz A, Hood S, Barber GG. Pharmacological management of intermittent claudication: a meta-analysis of randomised trials. Drugs. 2000;59(5):1057-1070.
Nathan, P. J., Harrison, B. J., and Bartholomeusz, C. Ginkgo and memory. JAMA. 2-5-2003;289(5):546-548.
Oh SM, Chung KH. Antiestrogenic activities of Ginkgo biloba extracts. J Steroid Biochem Mol Biol. 2006;100(4-5):167-76.
Persson, J., Bringlov, E., Nilsson, L. G., and Nyberg, L. The memory-enhancing effects of Ginseng and Ginkgo biloba in healthy volunteers. Psychopharmacology (Berl) 2004;172(4):430-434.
Pittler MH, Ernst E. Ginkgo biloba extract for the treatment of intermittent claudication: a meta-analysis of randomized trials. Am J Med. 2000;108(4):276-281.
Schneider LS, DeKosky ST, Farlow MR, Tariot PN, Hoerr R, Kieser M. A randomized, double-blind, placebo-controlled trial of two doses of Ginkgo biloba extract in dementia of the Alzheimer's type. Curr Alzheimer Res. 2005;2(5):541-51.
Snitz BE, et al; Ginkgo Evaluation of Memory (GEM) Study Investigators. Ginkgo biloba for preventing cognitive decline in older adults: a randomized trial. JAMA. 2009 Dec 23;302(24):2663-70.
Trick, L., Boyle, J., and Hindmarch, I. The effects of Ginkgo biloba extract (LI 1370) supplementation and discontinuation on activities of daily living and mood in free living older volunteers. Phytother Res. 2004;18(7):531-537.
Van Dongen, M., van Rossum, E., Kessels, A., Sielhorst, H., and Knipschild, P. Ginkgo for elderly people with dementia and age-associated memory impairment: a randomized clinical trial. J Clin Epidemiol. 2003;56(4):367-376.
Vellas, B., and Grandjean, H. Association of Alzheimer's disease onset with ginkgo biloba and other symptomatic cognitive treatments in a population of women aged 75 years and older from the EPIDOS study. J Gerontol A Biol.Sci.Med Sci. 2003;58(4):372-377.
Wang BS, Wang H, Song YY, Qi H, Rong ZX, Wang BS, Zhang L, Chen HZ. Effectiveness of standardized ginkgo biloba extract on cognitive symptoms of dementia with a six-month treatment: a bivariate random effect meta-analysis. Pharmacopsychiatry. 2010 May;43(3):86-91.
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