Ginkgo is the world’s most-used treatment for memory loss and degenerative diseases of the brain and central nervous system. It also aids treatment of a variety of conditions ranging from erectile dysfunction (ED) to ringing in the ears.
Ginkgo operates in the brain to lessen the progression of dementia probably by reducing white blood cell infiltration in the brain, curbing lipid peroxidation (preventing fat from going rancid), and increasing blood flow by antagonising platelet-activating factor (PAF). In one study, by boosting glucose levels using ginkgo, rats had increased mental capacity. Traditional Chinese medicine uses ginkgo for asthma, tinnitus, and angina.
The German Commission E has approved a limited number of specific standard extracts of ginkgo for symptomatic organic brain dysfunction, intermittent claudication, vertigo, and tinnitus. Ginkgo also has powerful antioxidant properties in the brain, the retina of the eye, and the cardiovascular system. This activity may help prevent free-radical damage and age-related declines in brain function.
Ginkgo should be recommended for at least 6 weeks before any assessment of clinical benefit is made.
maidenhair tree; Icho, Ityo, Pai Kuo, Yin Hsing, Yin Kuo, ying xing, hai guo
The Ginkgo is the world’s oldest living tree species dating to the Permian period, 200 million years ago. No one knows when ginkgos last grew wild, but for centuries, Chinese monks have grown ginkgo as a sacred tree and are credited with keeping the tree in existence. It was first brought to Europe around 1730, and its interesting leaves made ginkgo a cultivated favourite. The name comes from the Chinese yin-hing, meaning “silver apricot,” and refers to the resemblance of the orange fruits to miniature apricots. The leaves look like maidenhair fern leaves, giving it another name, the maidenhair tree.
Succeeds in most soil types so long as they are well-drained though it prefers a slightly dry loam in a position sheltered from strong winds. Some of the best specimens in Britain are found growing on soils over chalk or limestone. Plants flower and fruit more reliably after hot summers or when raised in a warm sunny position. Established plants are drought resistant, they also tolerate atmospheric pollution. Plants can grow in poor hard-packed soil, making the male forms good candidates for street planting. Trees are often used for street planting in towns, only the males are used because the fruit from female plants has a nauseous smell. The fruit contains butanoic acid, it has the aroma of rancid butter.
Antioxidant, antiplatelet activating factor (anti-PAF) activity, tissue perfusion enhancing, circulatory stimulant, cognition enhancing, neuroprotective
Symptomatic treatment of mild to moderate dementia syndromes, cerebral insufficiency and peripheral arterial occlusive disease. For the treatment of neurosensory disturbances such as dizziness, vertigo and tinnitus. Used to enhance cognitive performance.
Alzheimer’s disease, impaired cognition, memory loss, and Parkinson’s disease.
Ginkgo’s most exciting application may be in the treatment of impaired cognitive function. This disorder is at least partly related to an inadequate supply of glucose, or blood sugar, to the brain, which may alter functions of brain cells and their supporting structures. Ginkgo can both speed up the process by which the brain uses glucose and increase blood flow to the brain. The herb may also improve the brain’s use of a chemical called acetylcholine.
In one study, healthy elderly persons took 120 milligrams of ginkgo for twelve weeks, and memory and learning tasks were assessed by standardised tests. The participants felt better, but no improvements were seen in memory or learning. In another study, postmenopausal women who took a standardised ginkgo extract (120 milligrams daily) experienced an increase in mental flexibility after six weeks. In particular, women with an average age of sixty-one years made fewer errors and needed less time to complete mental tasks compared to those in a younger cohort (average age fifty-five years) who did not get these same benefits. In another study, ginkgo also was useful to elderly persons with normal cognitive function in that it prevented or delayed impairment of memory. Ginkgo has not been shown to be of help to young people, however. In a group of young people with an average age of twenty years, using two 60-milligram tablets of ginkgo (BioGinkgo) daily, there was no effect on a series of memory tests.
Researchers also have studied the use of ginkgo to treat older adults with either Alzheimer’s disease or mental debility caused by vascular dementia. Several studies have been published using ginkgo for Alzheimer’s disease. Unfortunately, many included inconsistent formulas of ginkgo and mixed the ginkgo with other herbs, making interpretation of the results problematic. One high-purity formula, ginkgo extract (EGb 761), had better and more consistent results. European investigators studying patients with Alzheimer’s disease and vascular dementia found that using EGb 761 resulted in improvements in tests of dementia compared to placebo and drug treatments. Increases were seen in attention, memory, and performance on cognition studies. Using this same extract (EGb 761), patients with uncomplicated, mild to moderate Alzheimer’s disease or dementia had improvement in cognitive performance and social functioning. Thus, a standardised ginkgo extract seems to be able to reverse deterioration associated with Alzheimer’s disease and dementia.
However, not all studies on the use of ginkgo for Alzheimer’s disease, mixed dementia, or vascular-related dementia have produced positive results. Nevertheless, it seems prudent to try ginkgo for impaired cognition, as the studies have all shown the herb to be safe.
In one study, ginkgo improved the efficacy and tolerability of chemotherapy in patients with advanced colon cancer. Patients were treated with 350 milligrams of ginkgo extract (EGb 761) as an infusion. There also was some evidence that the ginkgo actually slowed the progression of cancer. In another study, patients who suffered radiation exposure as a result of the Chernobyl accident also experienced a reduced risk of cancer from taking ginkgo. The dosage of ginkgo (EGb 761) used in this study was 40 milligrams three times a day. Additionally, in studies using cell lines, ginkgo teas (not extract tablets) that contain quercetin have shown some promise and may accelerate the death of leukemia and Burkitt’s lymphoma cells; slow the growth of colon, lung, and liver cancers; and inhibit the growth of estrogen-activated cancers, including bladder cancer, breast cancer, and, when used together with the chemotherapy drug cisplatin (Platinol), ovarian cancer.
Ginkgo can be used to treat depression in general by increasing the flow of oxygen to the brain. This is especially so for older adults if the herb is combined with appropriate prescription drugs, but you need to check with your doctor before combining this herb with any prescription drug. Other experiments show that the combination of ginkgo and ginger can reduce anxiety. Research suggests that ginkgo may be useful for elderly people with depression who are not responding to standard antidepressant drugs. One double-blind study found that older adults who had both depression and mild dementia, and who were not responding to antidepressant medications, reacted well to ginkgo supplementation.
Erectile dysfunction and diminished sexual desire.
One clinical study found that the use of 240 milligrams of ginkgo extract per day for six months resulted in a recovery of potency lost after treatment with drugs for depression. Ginkgo contains compounds that can cause the blood vessels to relax, resulting in greater blood supply to the penis and stronger erections. An open clinical study (one conducted without the use of placebos) found that 76 percent of men who experienced sexual problems caused by taking antidepressant drugs such as fluoxetine (Prozac), sertraline (Zoloft), or phenelzine (Nardil) recovered sexual function after four to six weeks of taking ginkgo. However, another study found no effect on sexual function in men and women who were using antidepressants when they were given 240 milligrams of ginkgo for twelve weeks. Still, ginkgo may have a beneficial effect in enhancing desire, excitement, orgasm, and afterglow in women who experience sexual difficulties as a result of taking antidepressants.
Intermittent claudication, heart attack, and stroke
Heart attack, stroke, and intermittent claudication (poor circulation that causes pain in the legs) all respond to treatment with ginkgo. The underlying factor in all of these conditions is atherosclerosis. When a blood vessel is damaged, PAF causes a leak-sealing clot to develop in the vessel wall and stimulates the production of fibrous tissues that cover the injury site. This provides a platform on which cholesterol may accumulate into a vessel-narrowing plaque. By deactivating PAF, ginkgo reduces the rate at which fibrous tissues are produced. The herb also helps to keep cholesterol-laden macrophages generated by the immune system from pumping even more cholesterol onto the arterial wall. In Germany, where ginkgo is prescribed for intermittent claudication, treatment usually brings relief in six weeks. In one study, most patients who took ginkgo in dosages that ranged from 120 to 160 milligrams for twenty-four weeks were able to walk for more extended periods pain-free compared to patients who received placebos.
Strokes can happen when a blood clot becomes stuck in a narrowed blood vessel in the brain. By inhibiting plaque development, ginkgo can protect against stroke. The herb also is helpful after a stroke. Much of the damage done by a stroke is caused by the formation of toxic free radicals when oxygen levels increase after circulation is restored. Brain cells cannot process all of the oxygen available to them, and some oxygen “escapes” its normal biochemical pathways. Ginkgo increases the production of scavengers that collect the oxygen free radicals before they can attack the linings of cells. Although these actions have been shown to happen in cell lines and animal studies, studies on stroke patients have not shown that taking ginkgo promotes recovery following an acute ischemic stroke in physical performance or on a brain scan.
In one study, ginkgo extract EGb 761 (20 milligrams daily) helped patients with multiple sclerosis. After four weeks, patients experienced improvements in fatigue, the severity of symptoms, and functionality. Several studies support the use of ginkgo in preventing relapses of multiple sclerosis. These studies indicate that ginkgo is more helpful when used long-term to prevent relapses than in the treatment of acute relapse symptoms.
Tinnitus, Sudden deafness
Ginkgo is frequently effective against tinnitus, or the sensation of constant ringing or buzzing noises in the ears if treatment begins within six to eight weeks of onset. A mini-review of five controlled studies showed favourable results. Doses of ginkgo were typically 120 to 160 milligrams a day. However, other studies conducted more recently did not find any benefit over placebo in cases of tinnitus. It also has been used in clinical trials to treat sudden hearing loss. In one study, up to 40 percent of the subjects regained their hearing after ten days of ginkgo treatment, and it was as effective as pentoxifylline, a drug that is typically used to treat hearing loss. The use of ginkgo or any other herb, however, does not substitute for immediate medical evaluation of tinnitus or hearing loss, since certain conditions cannot be treated with herbs or supplements, and are medically treatable only if promptly diagnosed.
- A critical review of 40 clinical trials conducted from 1975 to 1991 on the clinical use of standardized Ginkgo extracts in patients with cerebral insufficiency and related conditions (primary degenerative dementia; dizziness associated with labyrinth, vestibular disorders, or both; acute cochlear deafness; senile cognitive decline: and tinnitus) found that all except one of the 40 trials showed positive results, with significant results in 26. The inconclusive result was obtained for a trial on senile dementia of vascular origin. In most of the trials, the daily dose was 120 to 160 mg of standardised extract, given for at least 4 to 6 weeks. Meta-analysis of I1 randomised, double-blind, placebo-controlled trials confirmed the global effectiveness of Ginkgo in five studies and concluded that standardised Ginkgo extract provides a better therapeutic effect compared with placebo in treating cerebral insufficiency. In most cases, 150 mg/day was administered for 12 weeks.
- Improvements in cerebral blood flow, motor recovery, intellectual performance, memory, mood, and behaviour were observed in recent stroke victims after treatment with standardised Ginkgo extract in uncontrolled and in randomised, double-blind, placebo-controlled, and comparative trials. Although the general dosage used was 120 mg/day of standardised extract for 1 to 2 months in one of these trials, some patients received up to 360 mg/day.
- A meta-analysis of four randomised, double-blind, placebo-controlled trials found a small but significant effect after 3 to 6 months treatment with 120 to 240 mg/day of standardised Ginkgo extract on objective measures of cognitive function in patients with Alzheimer’s disease. A subsequent randomised, double-blind, placebo-controlled, multicenter trial in patients with mild to severe Alzheimer’s disease or multi-infarct dementia found that, compared with baseline values, treatment with standardised Ginkgo extract (120 mg/day for 26 weeks) slightly improved daily living and social behaviour and cognitive assessment. The placebo group showed a statistically significant worsening in all domains of assessment. Regarding safety, no differences between Ginkgo and placebo were observed.
- Two randomised, double-blind trials (included in the previously mentioned meta-analysis) demonstrated that standardised Ginkgo extract improved the cognitive performance and social function of patients with mild to severe Alzheimer’s disease or multi-infarct dementia compared with placebo. No significant difference compared with placebo was observed in the number of patients reporting adverse events or in the incidence and severity of these events. The dosage administered in these trials was 240 mg/day for 24 weeks and 120 mg/day for 52 weeks. A recent meta-analysis found no significant differences between standardised Ginkgo extract and four cholinesterase inhibitors (tacrine, donepezil, rivastigmine, and metrifonate) for delaying symptom progression in Alzheimer’s disease or response rate compared with placebo. The authors suggested that all treatments compared were equally efficacious in treating mild to moderate Alzheimer dementia.
- Supplementation with standardised Ginkgo extract (120 mg/day for 4 months) improved mood, sleep and coping ability for daily activities in a randomised, placebo-controlled study involving 5028 free-living elderly volunteers.
- In a randomised, double-blind, placebo-controlled study involving healthy adults, standardised Ginkgo extract (100 mg/day for 30 days) produced a significant improvement in a wide range of cognitive abilities, including long-term memory and abstract reasoning, using the multidimensional aptitude battery. Standardised Ginkgo extract (180 mg/day for 6 weeks) significantly increased cognitive processing speed and subjective ratings of memory improvement, compared with placebo, in cognitively intact older adults (55 to 86 years of age) in a randomised, double-blind, placebo-controlled. parallel-group study. The effects of acute doses of standardised Ginkgo extract on memory and psychomotor performance in asymptomatic volunteers aged 30 to 59 years was tested in a randomised, double-blind, placebo-controlled, five-way crossover design. The results confirm that the effects of Ginkgo on cognition are more pronounced for memory, mainly working memory. The most efficacious dose was a single dose of 120 mg, and the cognitive enhancing effects were more likely to be apparent in individuals aged 50 to 59 years. In a double-blind, controlled, crossover trial, acute administration of standardised Ginkgo extract (240 mg and 360 mg) to healthy young volunteers produced sustained improvement in attention compared with placebo. A randomised, double-blind, placebo-controlled trial demonstrated a significant increase in speed of information processing, working memory, and executive processing for healthy volunteers treated with standardised Ginkgo extract.
- A combination containing standardised extracts of Ginkgo (120 mg/day) and Korean ginseng (200 mg/day standardised to 4% ginsenosides) demonstrated improvement in the working and long-term memories of healthy middle-aged volunteers after 14 weeks in a multicenter, double-blind, placebo-controlled trial.
- In a meta-analysis that included five placebo-controlled trials, standardised Ginkgo extract (120 to 160 mg/day for 4 to 6 weeks) was found to have a highly significant therapeutic effect over placebo in peripheral arterial occlusive disease (Fontaine stage II or III). A review of randomised, double-blind, placebo-controlled trials of either standardised Ginkgo extract (120 to 160 mg/day) or the drug pentoxifylline in treating intermittent claudication found that the trials had similar clinical outcomes and were of the same methodological quality. Eight randomised, double-blind, placebo-controlled trials were included in a recent meta-analysis, concluding that standardised Ginkgo extract was superior to placebo in the symptomatic treatment of patients with intermittent claudication. The daily dose in these trials ranged from 120 mg to 160 mg for 24 weeks in six of the trials and for a shorter duration in the other trials.
- A review of randomised controlled trials found inconsistent results for Ginkgo in treating patients with tinnitus without accompanying symptoms of cerebral insufficiency. A large, double-blind, placebo-controlled trial published in early 2001 found that standardised Ginkgo extract (150 mg/day) was no more beneficial than was placebo in treating tinnitus. The treatment did not significantly affect other symptoms of cerebral insufficiency. Given the positive results of previous trials, the authors suggested that Ginkgo appears ineffective in treating tinnitus alone, but it may be useful in treating tinnitus in patients who also have other symptoms of cerebral insufficiency.
- A randomised trial comparing standardised Ginkgo extract (160 mg/day) and betahistine (a vasodilator, 32 mg/day) demonstrated the efficacy of both treatments on subjective and objective measurements of equilibrium in patients complaining of vertigo, dizziness, or both caused by vascular vestibular disorders. The results indicated that the sites of action of Ginkgo and betahistine for compensation of equilibrium are different and that Ginkgo improved oculomotor and visuovestibular function to a greater extent.
- A significant borderline benefit for Ginkgo over naftidrofuryl (a vasodilator) in idiopathic sudden hearing loss (existing no longer than 10 days) was shown after 3 weeks’ treatment in a randomised, comparative study. Ginkgo treatment was preferred because of the lack of side effects. Both treatment groups also received infusion therapy.
- A randomised, double-blind, placebo-controlled trial found standardised Ginkgo treatment (containing 48 mg/day flavone glycosides for 10 weeks) was unable to prevent the development of the symptoms of winter depression (the most prevalent type of seasonal affective disorder). Standardised Ginkgo extract (240 mg/day) improved sleep in patients with major depression. In this open, pilot trial, patients taking the antidepressant trimipramine plus Ginkgo were compared with those taking the drug alone.
- In a multicenter, double-blind, placebo-controlled study, Ginkgo significantly improved breast tenderness and markedly improved oedema, anxiety, depression, and headaches in 165 women with congestive symptoms of PMS. Standardised Ginkgo extract was administered at 160 mg/day from day 16 to day 5 of the next menstrual cycle.
- In patients with blockage of veins in the retina, standardised Ginkgo extract improved blood vessels, visual acuity, the field of vision, near and far vision, and colour recognition in a randomised, double-blind, placebo-controlled trial. Marked improvements in vision in 86% of patients with inadequate blood supply to the retina (or the areas of the brain that interpret the signals from the eyes) were observed in an uncontrolled trial. The dosage of the standardised extract was 120 mg/day for 3 months. A small, double-blind, placebo-controlled trial found standardised Ginkgo treatment (160 mg/day for 6 months) improved visual acuity (compared with placebo) in patients with senile macular degeneration. A recent placebo-controlled study found acute administration of Ginkgo significantly increased end-diastolic velocity in the ophthalmic artery in healthy volunteers, indicating possible benefit for optic neuropathy linked to glaucoma and other ischemic ocular diseases. The dosage of standardised Ginkgo extract was 120 mg/day for 2 days.
- In a randomised, placebo-controlled trial, administering standardised Ginkgo extract (160 mg/day) for the duration of an expedition significantly prevented acute mountain sickness at moderate altitude (5400 meters, or over 17,700 feet) and decreased vasomotor disorders of the extremities.
- Ingestion of standardised Ginkgo extract (120 mg/day for 3 months) by healthy volunteers resulted in the inhibition of collagen-induced platelet aggregation and reduced urinary excretion of 11-dehydrothromboxane B2 (a metabolite of thromboxane A2 ).
- A high dose of a ginkgolide mixture (120 mg) inhibited PAF activity in healthy human volunteers in a small, double-blind, placebo-controlled study. The mixture contained 40% ginkgolide A, 40% ginkgolide B, and 20% ginkgolide C.
- Ginkgo limited free radical-induced oxidative stress generated throughout surgery in patients undergoing aortic valve replacement in a double-blind, placebo-controlled study. The dosage prescribed was 320 mg/day of standardised extract for 5 days before surgery.
- In small, uncontrolled trials standardised Ginkgo extract has:
• Significantly reduced fibrinogen levels and blood viscosity in out-patients with a long history of elevated levels (240 mg/day for 12 weeks)
• Increased hypoxia tolerance in healthy volunteers (200 mg/day for 1 week)
• Decreased clastogenic (a form of mutagenic) activity of blood taken from salvage personnel working on the Chernobyl reactor accident (120 mg/day for 2 months)
• Alleviated sexual dysfunction secondary to antidepressant drug use (average dose: 207 mg/day for 4 weeks)
• Improved peak flow rates in asthmatic children
• Caused significant clinical improvement in asthmatic adults
Dosage (Divided Daily)
• Dried Leaf: 8,000 – 10,000mg
• Ginkgolides: 120 – 250mg (24% Ginkgolides or 50:1)
• Tincture: 3 – 4 mL (2:1)
Ginkgo should be used with caution in patients on anticoagulant or antiplatelet medication.
Interactions with other drugs
Caution should be exercised when prescribing Ginkgo with warfarin and aspirin
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