- Fossil tree
- Maidenhair tree
- Kew tree
- Bai guo ye
For Patients & Caregivers
How It Works
Ginkgo does not improve memory or brain function, and does not prevent or decrease the occurrence of dementia or Alzheimer’s disease.
Ginkgo biloba, one of the oldest living tree species, is used in traditional Chinese medicine and is also a popular supplement marketed to improve memory and circulation. Although some studies have observed these effects, large clinical trials do not support the use of ginkgo to improve memory or prevent memory loss. In addition, one study noted that ginkgo supplementation in older adults may increase stroke risk. Therefore, more studies are needed to determine risks and any benefits with ginkgo supplementation.
Ginkgo inhibits platelet-activating factor, which is important for blood clotting, and therefore has blood-thinning qualities.
To prevent memory loss or decline
In several large studies among elderly patients, ginkgo did not improve memory. It also did not prevent Alzheimer’s disease or dementia, and did not prevent what is commonly known as “brain fog” among cancer patients.
To manage cardiovascular disease
A large analysis did not find any benefit with ginkgo for heart disease.
To treat tinnitus
Studies are mixed on whether ginkgo can help tinnitus.
Do Not Take If
- You have a blood clotting disorder.
- You have a history of seizures.
- You are at risk for stroke: Ginkgo may increase this risk.
- You are taking warfarin or other blood thinners: Ginkgo may have additive effects, increasing the risk of spontaneous bleeding.
- You are taking antipsychotic medications or prochlorperazine: Case reports suggest ginkgo may cause seizures when combined with these medications.
- You are taking insulin: Ginkgo can alter insulin secretion and affect blood glucose levels.
- You are taking trazodone: In one case, ginkgo extract was associated with coma in a woman with Alzheimer’s disease who was also taking trazodone. Use with caution and ask your doctor.
- You are taking an antiretroviral such as efavirenz: Case reports suggest ginkgo may reduce the effectiveness of this drug.
- You are taking nonsteroidal anti-inflammatory drugs (NSAIDs): Ginkgo can increase adverse effects.
- You are taking amlodipine: Animal studies suggest ginkgo may increase the risk of side effects of this drug. Clinical relevance has yet to be determined.
- You are taking a CYP 3A4 substrate drug: Ginkgo may increase the risk of side effects of these drugs.
- You are taking a P-glycoprotein substrate drug: Ginkgo may increase the risk of side effects of these drugs.
- You are taking a UGT substrate drug: Lab studies suggest ginkgo may increase the risk of side effects of these drugs. Clinical relevance has yet to be determined.
Low blood levels of sodium: Several cases which caused confused state, malaise, headaches, and fatigue. This condition improved after ginkgo supplements were stopped.
Spontaneous bleeding: In a few cases, including in the eye and brain, related to ginkgo supplementation.
Prolonged bleeding: Among some healthy volunteers in a study that evaluated the interaction of ginkgo with antiplatelet drugs.
Seizures: In a few patients who were prone to seizures or on medications that lower the seizure threshold (e.g. prochlorperazine, chlorpromazine, perphenazine, etc.), ginkgo may have induced seizures.
Rash and itching: In a man after repeatedly ingesting a natural product containing ginkgo and vinpocetine.
Acute hemolytic anemia: In a patient after receiving a ginkgo injection for dementia. Symptoms resolved after IV fluids and discontinuation of product.
For Healthcare Professionals
Ginkgo biloba is one of the oldest living tree species. It is cultivated around the world for its medicinal properties and aesthetic value. The seeds and leaves have been used in traditional Chinese medicine to treat respiratory diseases, circulatory disorders, sexual dysfunction, and hearing loss. It is also marketed as a supplement to support memory and circulation.
Clinical studies including the large Ginkgo Evaluation of Memory (GEM) study generally show supplementation with ginkgo does not improve cognitive performance or prevent Alzheimer’s disease or dementia (4) (5) (6) (7) (8). In addition, positive effects from earlier studies were not confirmed in more recent trials and some systematic reviews determined there was insufficient evidence on any benefits in adults with either normal cognition or mild cognitive impairment (9) (10).
Although two trials suggest potential benefit with ginkgo in acute ischemic stroke (11) (12), a study in older adults noted increased stroke incidence (4), and a meta-analysis suggests evidence is generally weak with a high risk of bias (54). In addition, the large GEM study did not find benefit with ginkgo for cardiovascular disease incidence or mortality (13). Studies on whether ginkgo can help tinnitus are mixed (14) (15) (55) (56), as are studies for other conditions such as ADHD (16) (17).
Studies on ginkgo in cancer patients are quite limited (3) (21), and secondary outcome data from the aforementioned GEM study does not support the use of ginkgo to reduce cancer risk (22). It is also ineffective in preventing chemotherapy-associated cognitive dysfunction in breast cancer patients (23).
Although some preliminary data suggested ginkgo may reduce ovarian cancer risk (20), animal models suggest that high doses may have hepatocarcinogenic effects (24) (25). More studies are needed to determine the significance of these findings.
Mechanism of Action
Ginkgo interacts with several cytochrome P450 enzymes. Pretreatment with G. biloba extract induces expression of CYP3A proteins and mRNA and increases CYP3A activity (26). It also inhibits CYP2B6 catalytic activity and bupropion hydroxylation (27). Ginkgo may play a role in decreasing high-glucose-induced endothelial inflammation via inhibition of interleukin-6 activation (28), and repeated intake of ginkgo enhanced cell proliferation and neuroblast differentiation (29). Flavonoids present in ginkgo extracts inhibited estrogen biosynthesis via aromatase inhibition, decreased CYP19 mRNA, and induced transcriptional suppression (30).
Chemopreventive properties of bilobalide, a terpene trilactone, may occur via alterations in cryptal cell proliferation and drug-metabolizing enzyme activities (1). Exocarp polysaccharides from ginkgo affected expression of c-myc, bcl-2 and c-fos genes, which can inhibit proliferation and induce apoptosis and differentiation of human gastric tumor cells (3).
Hyponatremia: Several cases, which included symptoms of confused state, malaise, headaches, and fatigue. Plasma sodium normalized following cessation of ginkgo supplements (57).
Spontaneous bleeding: Including hematomas (31) (32), hyphema (33), and cerebral and intracerebral bleeding (34) (35).
Prolonged bleeding time: Among some healthy volunteers in a pharmacodynamic study that evaluated the interaction of ginkgo with antiplatelet drugs (36).
Seizures: In predisposed patients or those on medications that lowered the seizure threshold (37).
Cutaneous reaction: Pruritus and macular erythema in a man after repeatedly ingesting a natural product containing ginkgo and vinpocetine (38).
Acute hemolytic anemia (with injected ginkgo): In a patient with glucose-6-phosphate dehydrogenase (G6PD) deficiency receiving a G. biloba injection for dementia prophylaxis. Symptoms resolved following intravenous fluid infusion and discontinuation of G. biloba (39).
- Cytochrome P450 substrates: Laboratory studies and a few case reports suggest ginkgo can inhibit and induce the CYP450 1A2, 2D6, and 3A4 enzymes, but data are conflicting (26) (27) (40) (41) (42) (43). Clinical relevance has yet to be determined.
- P-glycoprotein substrates: In healthy volunteers, ginkgo inhibits P-glycoprotein and may interfere with drugs that are transported by P-glycoprotein (44).
- UGT (Uridine 5’-diphospho-glucuronosyltransferase) substrates: In vitro, ginkgo modulates UGT enzymes and may increase the side effects of drugs metabolized by them (45). Clinical relevance has yet to be determined.
- MATE1 substrates: Laboratory studies indicate that isorhamnetin, a compound present in ginkgo is a strong inhibitor of the human multidrug and toxic compounds extrusion transporter 1 (hMATE1), responsible for the excretion of various drugs in the kidney and liver (46). Clinical relevance has yet to be determined.
- Anticoagulants / Antiplatelets: Human studies and case reports indicate that ginkgo may induce or prolong bleeding time (36) (47).
- Nonsteroidal anti-inflammatory drugs (NSAIDS): Adverse event reports indicate that ginkgo can have additive anticoagulant/antiplatelet effects (48).
- Antipsychotics / Prochlorperazine: Case reports suggest ginkgo may cause seizures when combined with medications that lower the seizure threshold (37).
- Insulin: Laboratory and human studies suggest ginkgo can alter insulin secretion and affect blood glucose levels (49) (50).
- Trazodone: Ginkgo extract was associated with coma in a patient with Alzheimer’s disease who was also taking trazodone (47).
- Efavirenz: Case reports suggest ginkgo may inhibit the effects of this drug (43) (51).
- Midazolam: A study in healthy subjects suggests ginkgo may decrease serum concentrations (52).
- Amlodipine: Animal studies suggest that a multiherbal formula containing ginkgo could inhibit the metabolism of amlodipine (53). Clinical relevance has yet to be determined.