Ginkgo Biloba

Ginkgo (Ginkgo biloba) is one of the oldest tree species on the planet, a single surviving lineage with no close living relatives. The fan shaped leaves are the part used in modern phytotherapy. Standardised leaf extracts have been studied in European clinical research since the 1970s, primarily around cognitive function in older adults and around peripheral circulation. Ginkgo trees grow well in Vienna and in many other European cities, where they are valued as ornamental street trees rather than as a foraged medicine.

The European Medicines Agency (EMA HMPCEuropean Medicines Agency, Committee on Herbal Medicinal Products (HMPC)) recognises a well established medicinal use for a specific dry extract of Ginkgo leaf (EGb 761) in the symptomatic treatment of mild dementia. That is a medicinal product indication assessed by a regulator. It is not a claim that any food supplement on the shelf will reproduce that effect. A separate traditional use indication covers symptoms of capillary fragility (heaviness in the legs, mild swelling). Outside those regulatory frames the picture is mixed, and the entry treats it that way.

Ginkgo biloba is a living fossil. The species has been part of the East Asian flora for about two hundred million years and survived in cultivation around Buddhist temples in China and Japan long before Western botanists encountered it in the 18th century. The seeds and leaves both have a place in traditional Chinese medicine, but it is the leaf, not the seed, that anchors modern European phytotherapy.

Modern Ginkgo phytotherapy is a 20th century German project. The standardised leaf extract EGb 761, developed at the Schwabe laboratories from the 1960s onwards, defined the dosage form used in most clinical trials and remains the reference extract in the EMA HMPCEuropean Medicines Agency, Committee on Herbal Medicinal Products (HMPC) well established use monograph. The documented medicinal record for the species begins in the Chinese materia medica, where the seed (bai guo) is recorded for cough and wheezing, and the tree itself reached Europe only in the 18th century, long after the medieval herbal writers. It entered the European market as a modern phytopharmaceutical, and the entry treats it that way.

Standardised Ginkgo leaf extracts contain two main groups of bioactives. Flavone glycosides (around twenty four per cent in EGb 761, with kaempferol, quercetin and isorhamnetin derivatives as the main components) and terpene lactones (around six per cent in EGb 761, made up of ginkgolides A, B and C, plus bilobalide). The standardised label values (twenty four per cent flavone glycosides, six per cent terpene lactones) are the regulatory standard for EGb 761 and the closely related LI 1370 extract. The extract is also defined by a maximum content of ginkgolic acids (below 5 parts per million) because of allergenic concerns at higher levels.

Proposed mechanisms in the published literature include vasodilation and improved microcirculation, antioxidant activity at the level of mitochondrial membranes, and platelet activating factor antagonism (mainly attributed to ginkgolide B). The platelet activating factor pathway is the mechanism most often cited in discussions of the bleeding interactions covered in the safety section. The link between any specific bioactive and a specific clinical effect in people is plausible but not firmly established, and a meaningful share of the older mechanistic work is in vitro or in animal models rather than in controlled human trials.

The Cochrane review by Birks and Grimley Evans (2009) summarised more than thirty randomised controlled trials of Ginkgo extracts in people with cognitive impairment or dementia. The conclusion was mixed. Some trials, particularly those using EGb 761 at 240 mg per day over six months, showed measurable improvements on cognitive scales and on clinician rated impressions of change. Other trials showed no benefit over placebo. The Cochrane authors described the overall evidence as inconsistent and rated the methodological quality of many older trials as low to moderate.

The Ginkgo Evaluation of Memory (GEM) study reported by DeKosky et al. in 2008 was a large multi centre trial of EGb 761 at 240 mg per day for the prevention of all cause dementia in older adults. It enrolled more than three thousand participants over six years and did not find a preventive benefit. The combined reading across Birks 2009 and DeKosky 2008 is that there is a real signal for symptomatic treatment of mild dementia with one specific extract at one specific dose (which is why EMA HMPCEuropean Medicines Agency, Committee on Herbal Medicinal Products (HMPC) recognised the well established use indication) and no convincing evidence that Ginkgo prevents dementia in healthy adults. A separate small body of research covers peripheral arterial disease (intermittent claudication, walking distance); the signal there is weak and inconsistent.

Forms and preparation

In modern phytotherapy the relevant form is a standardised dry leaf extract in capsules or tablets. EGb 761 and the closely related LI 1370 are the two extracts that account for most of the clinical research. When you buy a Ginkgo product, look on the label for the standardisation: twenty four per cent flavone glycosides and six per cent terpene lactones is the reference. Products that do not declare this standardisation are not comparable to the research extracts and should not be assumed to reproduce the same effects. Fresh Ginkgo leaves and home made teas are not the same product as the standardised extract. Fresh leaf preparations contain ginkgolic acids at much higher levels than the regulated extract maximum (5 ppm), with a real allergenic risk on contact and an irritant risk when ingested. The fan leaves you see on a Vienna street tree are not a foraging target. Take Ginkgo only as a standardised commercial extract from a reputable manufacturer.

Dosage

The dose used in the EMA HMPC well established use indication and in the bulk of the cognitive trials is 240 mg per day of a standardised dry leaf extract (EGb 761 or LI 1370), taken as one dose or split into two doses with food. Lower doses (120 mg per day) appear in some older trials and remain on the market, mostly for the traditional use indication. Effects in the well established use indication are assessed over months, not days. Most trials in this space ran six months or longer. Start at the manufacturer recommended dose and do not stack Ginkgo on top of other blood thinning supplements (for example fish oil at high doses, garlic at high doses, vitamin E at high doses). If you are on a prescription anticoagulant, an antiplatelet, or chronic non steroidal anti inflammatory drugs, do not start Ginkgo without talking to your prescribing doctor first. The bleeding interaction is the gating safety question, not the dose itself.