Ginkgo biloba

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, since an early period in human history, and has various uses as a food and traditional medicine.

Ginkgoes are very large trees, normally reaching a height of 20–35 m (66–115 feet), with some specimens in China being over 50 m (164 feet). The tree has an angular crown and long, somewhat erratic branches, and is usually deep rooted and resistant to wind and snow damage. Young trees are often tall and slender, and sparsely branched; the crown becomes broader as the tree ages. During autumn, the leaves turn a bright yellow, then fall, sometimes within a short space of time (1–15 days). A combination of resistance to disease, insect-resistant wood and the ability to form aerial roots and sprouts makes ginkgos long-lived, with some specimens claimed to be more than 2,500 years old.

Ginkgo is a relatively shade-intolerant species that (at least in cultivation) grows best in environments that are well-watered and well-drained. The species shows a preference for disturbed sites; in the “semi-wild” stands at Tian Mu Shan, many specimens are found along stream banks, rocky slopes, and cliff edges. Accordingly, Ginkgo retains a prodigious capacity for vegetative growth. It is capable of sprouting from embedded buds near the base of the trunk (lignotubers, or basal chi chi) in response to disturbances, such as soil erosion. Old individuals are also capable of producing aerial roots (chi chi) on the undersides of large branches in response to disturbances such as crown damage; these roots can lead to successful clonal reproduction upon contacting the soil. These strategies are evidently important in the persistence of Ginkgo; in a survey of the “semi-wild” stands remaining in Tian Mu Shan, 40% of the Ginkgo specimens surveyed were multi-stemmed, and few saplings were present.[3]

Medicinal use…

Extracts of Ginkgo leaves contain flavonoid glycosides and terpenoids (ginkgolidesbilobalides) and have been used pharmaceutically. Ginkgo supplements are usually taken in the range of 40–200 mg per day. Recently, careful clinical trials have shown Ginkgo to be effective in treating dementia[30] but not preventing the onset of Alzheimer’s Disease in normal people.[31][32]

In memory enhancement

Ginkgo is believed to have nootropic properties, and is mainly used as memory[33] and concentration enhancer, and anti-vertigo agent. However, studies differ about its efficacy. The largest and longest independent clinical trial to assess Ginkgo biloba’s ability to prevent memory loss has found that the supplement does not prevent or delay dementia or Alzheimer’s disease.[34] Some controversy has arisen over the conclusions drawn by some studies that were funded by a firm which marketed Ginkgo.[35]

In 2002 a long-anticipated paper appeared in JAMA titled “Ginkgo for memory enhancement: a randomized controlled trial.” This Williams College study, sponsored by the National Institute on Aging rather than Schwabe, examined the effects of ginkgo consumption on healthy volunteers older than 60. The conclusion, now cited in the National Institutes of Health‘s ginkgo fact sheet, said: “When taken following the manufacturer’s instructions, ginkgo provides no measurable benefit in memory or related cognitive function to adults with healthy cognitive function.”[36] … The impact of this seemingly damning assessment, however, was ameliorated by the almost simultaneous publication of a Schwabe-sponsored study in the less prestigious journal Human Psychopharmacology. This rival study, conducted at Jerry Falwell’s Liberty University, was rejected by JAMA, and came to a very different—if not exactly sweeping—conclusion: There was ample evidence to support “the potential efficacy of Ginkgo biloba EGb 761 in enhancing certain neuropsychological/memory processes of cognitively intact older adults, 60 years of age and over.”

According to some studies, Ginkgo can significantly improve attention in healthy individuals.[37][38] In one such study, the effect was almost immediate and reaches its peak in 2.5 hours after the intake.[39]

One study suggests that Ginkgo’s effect on cognition may be attributable to its inhibitory effect on norepinephrine reuptake.[40]

In dementia

Ginkgo has been proposed as a treatment for Alzheimer’s disease on the basis of positive preclinical results in mice[41]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.[42] 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.[43][44] A similar trial published in the same journal in 2010, however, found ginkgo effective at treating mild to moderate dementia at the higher dose of 240 mg daily.[45] Another randomized controlled trial, published in JAMA in 2009, found no benefit from ginkgo in preventing cognitive decline or dementia.[32] 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.[30]

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)[46] that have been related to the development of a number of cardiovascular, renal, respiratory and central nervous system disorders. Ginkgo can be used for intermittent claudication.

Some studies suggest a link between ginkgo and the easing of the symptoms of tinnitus.[47]

The World Health Organization[48] reports that the medicinal uses of ginkgo biloba that are supported by clinical data include treatment of the effects mild to moderate cerebrovascular insufficiency [49]as well as the effects of peripheralarterial occlusive diseases.[50] 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, andRaynaud’s disease, a condition in which the extremities such as fingers, toes, nose or ears, feel numb and cold.

Preliminary studies suggest that Ginkgo may be of benefit in multiple sclerosis, showing modest improvements in cognition[51] and fatigue[51] without increasing rates of serious adverse events in this population.

A study conducted in 2003 by the Department of Dermatology, Postgraduate Institute of Medical Education and Research in Chandigarh, India concluded that Ginkgo is an effective treatment for arresting the development of vitiligo.[52] A later study published in 2011 discussed the results of an open label pilot clinical trial of twelve patients taking 60 mg of gingko over 12 weeks. The study found the progression of vitiligo stopped in all participants; the total VASI (Vitiligo Area Scoring Index) indicated an average repigmentation of vitiligo lesions of 15%. The authors conclude “Larger, randomized double-blind clinical studies are warranted and appear feasible.” [53]

Side effects

Ginkgo may have undesirable effects, especially for individuals with blood circulation disorders and those taking anticoagulants such as ibuprofenaspirin, 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.[54][55] Ginkgo should also not be used by people who are taking certain types of antidepressants (monoamine oxidase inhibitors and selective serotonin reuptake inhibitors[56][57]) or by pregnant women, without first consulting a doctor.

Ginkgo side effects and cautions include: possible increased risk of bleeding, gastrointestinal discomfort, nauseavomitingdiarrhea, headaches, dizziness, heart palpitations, and restlessness.[57][58]If any side effects are experienced, consumption should be stopped immediately.

Allergic precautions and contraindications to use

People taking pharmaceutical blood thinners such as warfarin or coumadin should consult with their doctor before taking Gingko biloba extracts, as it acts as an anti-coagulant.

The presence of amentoflavone in Gingko biloba leaves would indicate a potential for interactions with many medications through the strong inhibition of CYP3A4 and CYP2C9; however, there is a lack of any empirical evidence supporting this. It is possible that the concentration of amentoflavone found even in commercial Gingko biloba extracts is too low to be pharmacologically active.

Ginkgo biloba in Morlanwelz-MariemontPark, Belgium

Ginkgo biloba leaves also contain long-chain alkylphenols together with the extremely potent allergens, the urushiols (similar to poison ivy).[29] Individuals with a history of strong allergic reactions to poison ivy, mangoes, and other urushiol-producing plants are more likely to experience an adverse reaction when consuming Ginkgo-containing pills, combinations, or extracts.

 

{Information courtesy Wikipedia}