120–240 mg/day of standardized extract (EGb 761).
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Ginkgo biloba is one of the oldest trees on the planet (a living fossil whose evolutionary line goes back more than 200 million years), whose fan-shaped leaves have been used in traditional Chinese medicine for centuries and, in recent decades, have become one of the best-selling supplements in Europe and the Americas for cognition, especially in older adults with memory problems; the clinical evidence is heterogeneous and deserves an honest look to understand what it can and cannot offer.
The relevant active compounds are flavonoids (ginkgo flavone glycosides) and terpenoids (ginkgolides, bilobalide), a combination with effects on cerebral circulation (vasodilation of microvessels), platelet antiaggregation (especially via inhibition of platelet-activating factor), neurotransmitter modulation, and neuronal antioxidant protection; standardized extracts (EGb 761 is the most studied, found in Tebonin, Tanakene, Rökan) are the ones that have generated practically all the serious clinical evidence on the plant.
Meta-analyses on Ginkgo biloba in dementia (Alzheimer's disease, vascular dementia, mixed dementia) show modest but significant effects on cognition and activities of daily living with doses of 240 milligrams daily of EGb 761 for at least 22 weeks; the effect is comparable to that of first-generation acetylcholinesterase inhibitors (low-dose donepezil) in some head-to-head trials, with a better tolerability profile and without the complex drug interactions of anticholinesterases.
In people with mild cognitive impairment, the data are weaker but point to a possible reduction in progression to dementia with long-term use (years), although the most rigorous trials (GuidAge, the GEM Study in the US) found no significant reduction in the risk of incident dementia in healthy older people taking Ginkgo for 4-8 years, which has dampened the initial enthusiasm for its preventive use in the general population.
In healthy young adults, the effects on "normal" cognition are small or inconsistent in serious meta-analyses: some acute improvements in processing speed and working memory with single high doses, but no significant effects with chronic use in people without prior cognitive impairment; Ginkgo is not a general-purpose nootropic useful for "improving the brain" of healthy people, an uncomfortable truth for a significant part of the product's marketing.
In chronic tinnitus, several trials have shown modest improvements with EGb 761 at 240 mg/day for 12 weeks, especially in tinnitus of recent vascular origin; in intermittent claudication (leg pain when walking due to peripheral arterial insufficiency), several trials have shown 20-40 percent increases in pain-free walking distance with 120-240 mg/day for 6 months, an indication where the effect on microcirculation appears clinically useful.
In glaucoma and age-related macular degeneration, there are interesting preliminary data that are not yet consolidated; in generalized anxiety and adult ADHD, some small studies suggest modest benefits, but the evidence is limited compared with other, better-established therapeutic options.
The doses studied range from 120 to 240 milligrams daily of standardized EGb 761 (24 percent ginkgo flavone glycosides, 6 percent terpenoids), divided into two servings with or without food; the clinical effect requires prolonged use (at least 8-12 weeks for cognitive indications, 6 months for claudication) and persists for as long as treatment continues.
The most important precaution is the risk of bleeding: Ginkgo has a significant antiplatelet effect (it inhibits platelet-activating factor) that adds to that of any anticoagulant or antiplatelet drug; people taking warfarin, acenocoumarol, aspirin, clopidogrel, or NSAIDs should exercise particular caution, and it is recommended to stop it at least one week before any elective surgery; it is advisable to avoid it in pregnancy, breastfeeding, and bleeding disorders.
Information, not medical advice. Scientific evidence reflects the quality of the studies.