Also Known As: Ginkgo biloba, Ginkgo, Gingko, Maidenhair Tree
Ginkgo is a genus of highly unusual non-flowering plants with one extant species, G. biloba, which is regarded as a living fossil.
Ginkgo (Ginkgo biloba; in Chinese and Japanese 銀杏, pinyin romanization: yín xìng, Hepburn romanization: ichō or ginnan), also spelled gingko and known as the Maidenhair Tree, is a unique species of tree with no close living relatives. The tree is widely cultivated and introduced early in human history, and has various uses as a food and in traditional medicine.
Extracts of Ginkgo leaves contain flavonoid glycosides and terpenoids (ginkgolides, bilobalides) and have been used pharmaceutically. Ginkgo supplements are usually taken in the range of 40–200 mg per day. Recently, a meta-analysis of clinical trials have shown Ginkgo to be moderately effective in improving cognition in dementia patients but not preventing the onset of Alzheimer's Disease in normal people.
Ginkgo is believed to have nootropic properties, and is mainly used as memory and concentration enhancer, and anti-vertigo agent. However, studies differ about its efficacy. The largest and longest independent clinical trial conducted by the Journal of the American Medical Association (JAMA) to assess Ginkgo biloba published the finding in 2008 that the supplement does not reduce incidence of all-cause dementia or Alzheimer disease in adults 75 years or older who had normal cognition or mild cognitive impairment when given a twice-daily dose of 120 mg extract of G. biloba. However, a similar trial published in 2010 by the International Journal of Geriatric Psychiatry concluded that the same extract formulation of G. biloba (EGb 761), when given as a single 240 mg daily dose, "was found significantly superior to placebo in the treatment of patients with dementia with neuropsychiatric symptoms."
According to some studies, Ginkgo can significantly improve attention in healthy individuals. In one such study, the effect was almost immediate and reaches its peak in 2.5 hours after the intake.
One study suggests that Ginkgo's effect on cognition may be attributable to its inhibitory effect on norepinephrine reuptake.
Ginkgo has been proposed as a treatment for Alzheimer's disease on the basis of positive preclinical results in mice and a 2006 study that found 160 mg of ginkgo extract as effective as a daily 5 mg dose of the cholinesterase inhibitor donepezil in human subjects. A 2008 randomized controlled clinical trial published in the International Journal of Geriatric Psychiatry found gingko ineffective at treating dementia in humans at a daily dose of 120 mg. A similar trial published in the same journal in 2010, however, found ginkgo effective at treating mild to moderate dementia at the higher single dose of 240 mg daily. Another randomized controlled trial, published in JAMA in 2009, found no benefit from ginkgo in preventing cognitive decline or dementia when given at a dose of 120 mg twice daily. A recent meta-analysis of nine studies of ginkgo for use in the treatment of dementia concluded that it was more effective than placebo although, like other dementia drugs, the clinical significance of these moderate effects was difficult to quantify.
In other symptoms
Out of the many conflicting research results, Ginkgo extract may have three effects on the human body: improvement in blood flow (including microcirculation in small capillaries) to most tissues and organs; protection against oxidative cell damage from free radicals; and blockage of many of the effects of platelet-activating factor (platelet aggregation, blood clotting) that have been related to the development of a number of cardiovascular, renal, respiratory and central nervous system disorders. Ginkgolides, especially ginkgolide B, are potent antagonists against platelet-activating factor; and thus may be useful in protection and prevention of thrombus, endotoxic shock, and from myocardial ischeamia. Ginkgo can be used for intermittent claudication.
Ginkgo has been studied as a potential treatment for sexual dysfunction related to SSRI use, but failed to show any effectiveness in placebo-controlled trials.
The World Health Organization reports that the medicinal uses of Ginkgo biloba that are supported by clinical data include treatment of the effects mild to moderate cerebrovascular insufficiency  as well as the effects of peripheral arterial occlusive diseases. Cerebrovascular insufficiency, i.e., insufficient blood flow to the brain, may manifest itself as such memory deficit, disturbed concentration or headaches. Peripheral arterial occlusive diseases are those in which the blood flow to the smaller arteries are restricted and may include claudication, i.e., painful walking, and Raynaud's disease, a condition in which the extremities such as fingers, toes, nose or ears, feel numb and cold.
Preliminary studies suggested that Ginkgo might be of benefit in multiple sclerosis, but clinical trials failed to show any effect on cognitive function in MS patients.
Ginkgo may have undesirable effects, especially for individuals with blood circulation disorders and those taking anticoagulants such as ibuprofen, aspirin, or warfarin, although recent studies have found that ginkgo has little or no effect on the anticoagulant properties or pharmacodynamics of warfarin in healthy subjects. Ginkgo inhibits monoamine oxidase, and therefore should not be used by people who are taking certain types of antidepressants (monoamine oxidase inhibitors and selective serotonin reuptake inhibitors) or by pregnant women, without first consulting a doctor.
Ginkgo side effects and cautions include: possible increased risk of bleeding, gastrointestinal discomfort, nausea, vomiting, diarrhea, headaches, dizziness, heart palpitations, and restlessness. If any side effects are experienced, consumption should be stopped immediately.