Bottom Line: Ginkgo does not improve memory or cognitive functioning in healthy people. It was also found ineffective in decreasing the occurence of dementia or Alzheimer's disease in elderly individuals.
Scientists have found that in animals and humans, ginkgo dilates blood vessels in the brain 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 the tone of the smooth muscle 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 No scientific evidence supports this use.
To treat asthma and bronchitis A single study conducted in China supports this use.
To manage heart disease No scientific evidence supports this use.
To treat circulatory problems Studies in animals and humans have shown that ginkgo can increase blood flow, but no clinical trials have definitively supported this use.
To treat sudden hearing loss Several clinical trials support this use.
To treat tinnitus There is no data to support this use.
To prevent memory loss Although several clinical trials support this use in patients with dementia, one recent clinical trial suggests that healthy adults do not seem to benefit from ginkgo.
To treat dementia and Alzheimer's disease Several clinical trials support this use, although one recent clinical trial did not.
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 in one clinical trial.
To treat acute mountain sickness Data is conflicting on whether Gingko biloba is useful in treating acute mountain sickness.
Memory enhancement in healthy persons: A recent clinical trial randomly assigned 98 men and 132 women in good health to take 40 mg of ginkgo biloba extract or a placebo extract three times a day for six weeks. After six weeks, the men and women were tested for memory, attention, language, and concentration, and it was found that people taking ginkgo performed about the same as people taking the placebo. This indicates that ginkgo does not improve memory or concentration in healthy adults.
Dementia or Alzheimer's disease: The effects of ginkgo use on memory loss were studied in a large randomized, controlled trial. For 24 weeks, 214 elderly people with dementia or age-related memory loss were randomly split into three groups and were given 160 mg of ginkgo, 240 mg of ginkgo, or a placebo pill daily. After 12 weeks, the ginkgo users were again split up and assigned to continue taking their previous ginkgo dosage or a placebo pill. Overall, the researchers found that ginkgo had no significant effect on memory in these patients. These results are unlike previous studies, which did find a benefit from ginkgo use.
Two hundred and forty-four patients with uncomplicated Alzheimer's disease or dementia enrolled in a clinical trial to study the effects of ginkgo extract. For six months, these patients took a 120 mg dose (40 mg three times a day) of ginkgo or a placebo pill three times a day. The placebo group showed a significant worsening in all symptoms, while the ginkgo group was slightly improved. No serious side effects were reported. This study suggests that ginkgo may help prevent progression of dementia or Alzheimer's disease.
Another clinical trial studied ginkgo in 309 patients with mild to severe dementia associated with either Alzheimer disease or dementia. The patients were randomly split into two groups, one to receive treatment with a placebo pill, and the other to receive ginkgo extract at a dose of 40 mg three times a day - a total daily dose of 120 mg. After one year of treatment, a higher percentage of the patients treated with ginkgo showed improvement in cognitive abilities, social behavior, and daily living. The researchers concluded that ginkgo appears to stabilize and, in some cases, improve the patient's functioning. The adverse events associated with ginkgo were no different from those associated with the placebo.
The effects of ginkgo were again studied in patients with either Alzheimer disease or dementia in a randomized, controlled trial. The researchers found that, after six months, a greater percentage of patients taking ginkgo showed symptom improvement compared to patients taking the placebo pill. Patients with Alzheimer's disease appeared to respond to ginkgo treatment better.
Ginkgo biloba extracts should be checked to make sure they do not contain ginkgolic acid. Ginkgolic acid increases the risk of allergic reactions.
Ginko biloba should be discontinued at least 36 hours before surgery due to the risk of increased bleeding.
This product is regulated by the FDA as a dietary supplement. Unlike approved drugs, supplements are not required to be manufactured under specific standardized conditions. The product may not contain the labeled amount or may be contaminated. In addition, it may not have been tested for safety or effectiveness.
You are at risk of 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).
Contact dermatitis (redness, swelling, and irritation of the skin)
Palpitations
Case reports: 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 handful of 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.
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 medicine to treat respiratory diseases, circulatory disorders, sexual dysfunction, and loss of hearing. Ginkgo biloba extract exhibits anti-infective (1), chemopreventive (2), anticancer (3), and cytotoxic (4) effects in vitro. Supplementation with Ginkgo improved cognitive performance in healthy adults (5), and demented patients (6) but data are conflicting (7)(8)(9)(10)(11). However, findings from the Gingko Evaluation of Memory (GEM) study, the largest trial of Ginkgo for dementia so far, indicate that Ginkgo is ineffective in decreasing the incidence of dementia or Alzheimer's disease in elderly individuals (30). Ginkgo biloba may also reduce the severity of acute mountain sickness, but the evidence is mixed (25)(26)(27)(28). More studies are warranted. Ginkgo has also been implicated in reducing the risk of ovarian cancer but this is based only on epidemiological and biological data (12). Orally administered capsules of Ginkgo biloba exocarp polysaccharides reduced 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). Further studies are needed to determine the anticancer potential of oral Ginkgo supplements.
Ginkgo use is associated with adverse effects and it can also interact with prescription medications. Ginkgo supplementation for dementia may increase risk of stroke (29). Patients should use caution before taking Ginkgo supplements.
The active constituents, bilobalide and ginkgolides, improve the tolerance of brain tissue to hypoxia by increasing cerebral blood flow. Ginkgo can increase blood flow to the brain through arterial vasodilatation by stimulating prostaglandin biosynthesis or indirectly stimulating norepinephrine release. Ginkgo has slight anti-inflammatory and spasmolytic activities that are similar to papaverine. It has free-radical scavenging activity for hydroxyl, nitric oxide, peroxyl, and superoxide radicals; it is as effective as uric acid. Ginkgo increases tolerance to ischemic conditions and seems to inhibit the platelet-activating factor. Animal studies have shown that ginkgo has a beneficial effect on neurotransmitter disturbance that can restore vascular tone of the smooth muscle cells by maintaining alpha-adrenergic constrictive and beta-adrenergic relaxation vaso-regulation. Ginkgo can also suppress cell proliferation, decrease levels of proliferating cell nuclear antigen, and increase expression of p53, a tumor suppressor gene, in human hepatocellular carcinoma cells (15).
Common: Headache, dizziness, GI upset, flatulence, diarrhea, contact dermatitis, and palpitations (14) Case reports: 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) and hyphema (20), was also reported. Products that contains ginkgolic acid may increase the risk of allergic reaction.
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). Drugs metabolized by Cytochrome P450: Preliminary evidence suggests that ginkgo can affect the CYP450 1A2, 2D6, and 3A4 enzymes. But because of conflicting data, it is not clear whether it induces or inhibits the individual enzymes (24). 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).
Van Dongen MC, et al. The efficacy of ginkgo for elderly people with dementia and age-associated memory impairment: new results of a randomized clinical trial. J Am Geriatr Soc 2000;48:1183-94. A 24 week, randomized, double-blind, placebo-controlled, parallel-group, multicenter trial. Two-hundred fourteen participants were allocated randomly to treatment with EGb 761, a special extract of ginkgo biloba, two tablets per day, total dosage either 240 mg or 160 mg/day or placebo. The total intervention was 24 weeks. After 12 weeks of treatment, the initial ginkgo users were randomized once again to either continued ginkgo treatment or placebo treatment. Initial placebo use was prolonged after 12 weeks. An intention-to-treat analysis showed no effect on each of the outcome measures for participants who were assigned to ginkgo compared with placebo for the entire 24-week period. After 12 weeks of treatment, the combined high dose and usual dose groups performed slightly better with regard to self-reported activities of daily life. No duration of ginkgo treatment was found. No adverse effects were noted. In conclusion, the results suggested that ginkgo was not effective as a treatment for older people with mild to moderate dementia or age-associated memory impairment. These results contrasted sharply with those of previous ginkgo reports.
LeBars, PL, et al. A placebo-controlled, double-blind, randomized trial of an extract of ginkgo biloba for dementia. JAMA 1997;278:1327-32. This placebo-controlled, double-blind study was designed to investigate the effects of a standardized extract in 309 patients with mild to severe dementia associated with either Alzheimer disease or multi-infarct dementia. Patients were randomized to receive 52 weeks of treatment with placebo or ginkgo extract at a dose 40 mg three times a day, a total daily dose of 120 mg. At 52 weeks, 202 patients were included in the endpoint analysis, which was based on standard tests of cognitive impairment, daily living and social behavior, and general psychopathology. The researchers reported that 27% of patients who received 26 or more weeks of treatment with ginkgo extract experienced at least a four-point improvement on the 70-point Alzheimer Disease Assessment Scale-Cognitive subscale, compared to 14% in the placebo group. Daily living and social behavior were deemed improved in 37% of ginkgo patients, compared to 23% of those taking placebo, as measured by Geriatric Evaluation by Relative's Rating Instrument (GERRI). In contrast, the GERRI showed that 40% of patients taking placebo experienced a worsening of their conditions, while worsening was seen in only 19% of those taking ginkgo. The researchers concluded that ginkgo appears to stabilize and, in an additional 20% of cases (vs. placebo), improves the patient's functioning for periods of six months to one year. The adverse events associated with ginkgo were no different from those associated with placebo.
