- Fossil tree
- Maidenhair tree; kew tree
- Bai guo ye
For Patients & Caregivers
Ginkgo does not improve memory or cognitive functioning in healthy people. It was also found ineffective in decreasing the occurrence of dementia or Alzheimer’s disease in elderly individuals.
Scientists have found that ginkgo dilates blood vessels in the brain in animals and humans, thereby increasing blood flow to the brain. This enables the body to handle ischemic (low oxygen) conditions, which can help prevent tissue damage. In animal studies, ginkgo showed a beneficial effect on smooth muscle tone found in arteries, maintaining their appropriate dilation and constriction. Experiments have also revealed that ginkgo can reduce inflammation and calm muscle spasms. As an antioxidant, it can also neutralize free radicals in the body, which cause cellular and DNA damage. Laboratory and animal experiments suggest that ginkgo can help prevent infections. Ginkgo also inhibits platelet-activating factor, which is important for blood clotting, and therefore has blood thinning qualities.
Ginkgo supplementation may increase risk of stroke.
- To reduce stress and anxiety
There are no data to back this claim.
- To treat asthma and bronchitis
A single study supports this use.
- To manage heart disease
There is no scientific evidence to support this claim.
- To treat circulatory problems
Studies in animals and humans have shown that ginkgo can increase blood flow, but clinical trials do not support this use.
- To treat sudden hearing loss
Several clinical trials support this use.
- To treat tinnitus
There are no data to support this use.
- To prevent memory loss
Although clinical trials support this use in patients with dementia, recent studies suggest that healthy adults may not benefit from ginkgo.
- To treat dementia and Alzheimer’s disease
Results from clinical studies are inconclusive.
- To treat Raynaud’s disease
Laboratory studies show that ginkgo can calm muscle spasms and maintain the tone of arteries, but these effects were not observed in human clinical trials.
- To treat sexual dysfunction
An herbal mixture containing ginkgo was found effective in treating sexual dysfunction.
- To treat acute mountain sickness
Data are conflicting on ginkgo’s ability in treating acute mountain sickness.
- 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 monoamine oxidase inhibitors (MAO-Is) (Ginkgo may have additive effects).
- You are taking warfarin or any other blood thinner (Ginkgo may have additive effects, increasing the risk of spontaneous bleeding).
- You are taking antipsychotic medication or prochlorperazine (Ginkgo may cause seizures when combined with these medications).
- You are taking insulin (Ginkgo can alter insulin secretion and effect 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 Nonsteroidal Anti-inflammatory drugs (NSAIDS) (Ginkgo can have additive anticoagulant/antiplatelet effects).
- You are taking drugs that are substrates of Cytochrome P450 3A4 (Ginkgo may increase the risk of side effects of these drugs).
- You are taking drugs that are substrates of P-Glycoprotein (Ginkgo may increase the risk of side effects of these drugs).
- You are taking Efavirenz (a antiretroviral drug) (Ginkgo may reduce its effectiveness).
- You are taking drugs that are substrates of UGT (Uridine 5’-diphospho-glucuronosyltransferase) enzymes (Ginkgo may increase the risk of side effects of these drugs).
- You are taking Amlodipine (a calcium channel blocker): (Ginkgo leaf tablet, a multiherbal formula containing ginkgo, may increase the risk of side effects of this drug).
- In a few patients who were predisposed to seizures or on medications that lower the seizure threshold (e.g. prochlorperazine, chlorpromazine, perphenazine, etc.), ginkgo may have induced seizures.
- A few cases of spontaneous bleeding, including hematomas (collections of blood in organs or tissues due to a broken blood vessel) and hyphema (hemorrhage within the eye), have been reported.
- A patient with glucose-6-phosphate dehydrogenase (G6PD) deficiency developed acute hemolytic anemia after receiving an injection of G. biloba for dementia. Her symptoms resolved following intravenous fluid infusion and discontinuation of G. biloba.
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 the leaves have been used in traditional Chinese medicine to treat respiratory diseases, circulatory disorders, sexual dysfunction, and loss of hearing. Ginkgo extracts exhibit anti-infective (1), chemopreventive (2), anticancer (3), and cytotoxic (4) effects in vitro. Supplementation with ginkgo improved cognitive performance in healthy adults (5), and in patients with dementia (6) although data are conflicting (7) (8) (9) (10) (11). In a study of older adults with normal cognition or with mild cognitive impairment (32), gingko did not slow down cognitive decline. And findings from the Gingko Evaluation of Memory (GEM) study, the largest trial of ginkgo for dementia to date, indicate that ginkgo is ineffective in decreasing the incidence of dementia or Alzheimer’s disease in elderly individuals (30); another randomized trial reported similar findings (43). However, ginkgo may be effective as a short-term treatment to improve memory in Alzheimer’s patients, although taking ginkgo supplements regularly does not prevent dementia (55). In other studies, it was found less effective than standard treatment for ADHD in children (37). Ginkgo may also reduce the severity of acute mountain sickness, but the evidence is mixed (25) (26) (27) (28). More studies are warranted.
Ginkgo’s anticancer potential has been explored as well. It has been implicated in reducing the risk of ovarian cancer, although based only on epidemiological and biological data (12). Orally administered capsules of ginkgo exocarp polysaccharides reduced the tumor area in patients with gastric cancer (4). In another study, an injectable form of ginkgo extract and 5-flurouracil were administered to patients with advanced colorectal cancer. Data suggests benefits of the combination therapy (13). But data from the GEM study, in which cancer was the secondary outcome, do not support gingko’s effectiveness in reducing cancer risk (38). Ginkgo supplementation was also reported ineffective in preventing chemotherapy-associated cognitive dysfunction in a randomized controlled trial of breast cancer patients (45).
Interestingly, high doses of a ginkgo extract showed carcinogenic effects in a murine model (44). However, dietary supplements in use today have much smaller concentrations of ginkgo.
Ginkgo interacts with several cytochrome P450 enzymes. Pretreatment with G. biloba extract was shown to induce the expression of CYP3A protein and mRNA, and increased CYP3A activity (34). It also inhibits CYP2B6 catalytic activity and bupropion hydroxylation (36). In other studies, ginkgo was shown to play a role in decreasing high-glucose-induced endothelial inflammation via inhibition of interleukin-6 activation (49), and repeated intake of Ginkgo enhanced cell proliferation and neuroblast differentiation (50). The flavonoids present in ginkgo extracts were found to inhibit estrogen biosynthesis via aromatase inhibition, decrease CYP19 mRNA, and induce transcriptional suppression. These findings suggest a role for ginkgo as an adjuvant treatment for breast cancer (56).
The present study demonstrated that three flavonoids synergistically inhibit estrogen biosynthesis through aromatase inhibition, decrease CYP19 mRNA, and induce transcriptional suppression. Our results support the usefulness of flavonoids in adjuvant therapy for breast cancer by reducing estrogen levels with reduced adverse effects due to estrogen depletion
The chemopreventive ability of bilobalide, a terpene trilactone, is thought to be via alterations in cryptal cell proliferation and drug-metabolizing enzyme activities (2). The exocarp polysaccharides from ginkgo were shown to affect the expression of c-myc, bcl-2 and c-fos genes, which can inhibit proliferation and induce apoptosis and differentiation of human gastric tumor cells (4).
Seizures were reported in patients predisposed to seizures or on medications that lower the seizure threshold (e.g. prochlorperazine, chlorpromazine, perphenazine, etc.) (17).
Spontaneous bleeding (18), including hematomas (15) (19), hyphema (20), and cerebral bleeding (41) have also been reported.
A patient with glucose-6-phosphate dehydrogenase (G6PD) deficiency developed acute hemolytic anemia after receiving an injection of G. biloba for dementia prophylaxis. Her symptoms resolved following intravenous fluid infusion and discontinuation of G. biloba (53).
- Monoamine oxidase inhibitors (MAO-I): Ginkgo may potentiate the effects of MAO-Is.
- Anticoagulants / Antiplatelets: Ginkgo may induce spontaneous bleeding possibly associated with reduced platelet aggregation resulting from inhibition of platelet activating factor by ginkgolide components (21).
- Antipsychotics / Prochlorperazine: Ginkgo may cause seizures when combined with medications that lower the seizure threshold (17).
- Insulin: Ginkgo can alter insulin secretion and affect blood glucose levels (22) (23).
- Cytochrome P450 substrates: Studies show that ginkgo can inhibit and induce the CYP450 1A2, 2D6, and 3A4 enzymes but data are conflicting (24) (34) (35) (36) (39) (40).
- P-Glycoprotein substrates: Ginkgo inhibits P-glycoprotein and can therefore interfere with drugs that are transported by P-glycoprotein (33).
- Trazodone: Ginkgo extract was associated with coma in a patient with Alzheimer’s disease who was also taking trazodone (21).
- Nonsteroidal Anti-inflammatory drugs (NSAIDS): Ginkgo can have additive anticoagulant/antiplatelet effects (31).
- Efavirenz: Ginkgo may inhibit its effects (40) (51)
- UGT (Uridine 5’-diphospho-glucuronosyltransferase) substrates: Ginkgo modulates UGT enzymes in vitro and can increase the side effects of drugs metabolized by them (42).
- Amlodipine: Ginkgo leaf tablet, a multiherbal formula containing ginkgo, was shown to inhibit the metabolism of amlodipine in a rat model (57).
Isorhamnetin, a compound present in ginkgo was shown to be a strong inhibitor of the human multidrug and toxic compounds extrusion transporter 1 (hMATE1), which is responsible for the final step of excretion of various xenobiotics in the kidney and liver (54).