Benefits and Dangers of Ginkgo biloba
The sale of Ginkgo supplements has been rising steadily all over the world. On average, people have bought over $150 million dollars worth of Ginkgo in the US. Ginkgo is marketed as an extract that can enhance memory and concentration, improve blood circulation and protect cells against oxidative damage. Many of these claims are now being endorsed by science.
There is no denying that the Ginkgo plant fascinates many. The Ginkgo tree is a unique species that has survived millions of years of evolution. It is a source of food, wood and medicine. It shows botanical characteristics that have mystified plant experts. In the far east there are Ginkgo trees that have lived through generations, some over 1500 years old. It is a symbol of longevity and endurance. It is the only tree that has survived the nuclear holocaust and still stands in Hiroshima as a survivor. It is no wonder that we hold this tree with much reverence, for what it represents and what it gives.
As with many herbal remedies, the Ginkgo extract falls under the category of food supplements and is therefore not governed by the strict rules of research, scrutiny and approval to reach the market. This allows the market to mix myth and mystery to facts. From the growth figures, it is clear that this marketing ploy and the word of mouth have been hugely successful.
Perhaps it is wise then, to consider fact from fiction and be a fully informed participant of the Ginkgo cult. I am aware that although the recommendation is to consult a health professional before one starts taking it, many may not feel it is necessary to do so. Perhaps you would consider it useful to know the benefits, risks and the interactions with other prescribed medication if you are one who are already taking Ginkgo or are planning to embark on it.
Ginkgo trees live very long due to a combination of factors such as high resistance to disease and insects, resistance to wind and snow damage and the ability to form aerial roots. Some ginkgo trees in china and Japan are believed to be over 2,500 years old.
A Ginkgo Leaf fossil
The Tree that time forgot
There is a reason why Ginkgo biloba is revered by some cultures. We know that many of our trees have transcended time, have existed before civilisation came into existence. Among all those mighty Oaks and ancient Ashes, Gingko stands tall and proud - for it is the only tree that we know of that has existed over 270 million years, unchanged, enduring and ever present.
Ginkgo biloba, is in fact , a living fossil. It is a unique species that has no known living relatives.
It is also a tree that nearly went extinct and was saved by humanity. It was once widespread all over the world and eventually shrank in its distribution to two small provinces of China. Botanical evidence suggests that even these were preserved by Chinese monks by cultivation and recultivation for over a thousand years until it was discovered by the western travellers and brought over to the other parts of the world.
Linnaeus described the species in his original treatise in 1771. The name Ginkgo is thought to be a mistranslation of its Japanese name ginnan by Engelbert Kaempfer who first reported the species in 1690 during his travels to Japan. The Japanese ideograms for gin-kyo and ginnan look similar and he had unintentionally taken the former pronunciation.
Etymology of Ginkgo biloba
銀果 ( yínguǒ)
China ( Mandarin)
白果 (bái guǒ)
The Ginkgo tree has a unique behaviour during fall. While other trees shed their leaves over a period of days or weeks, Ginkgo leaves fall simultaneously as if planned within a few hours. People call this 'Ginkgo rain'.
Apart from its longevity, Ginkgo also exhibits some unique morphological features. The Ginkgo leaf is a bi-lobed distinctive shape ( hence biloba). It has fan shaped veins radiating out to the tip - unlike other plants the veins don't conjoin and anastomose to form a network and remain distinct all the way towards the edges.
Ginkgo trees have distinct sexes - a male and a female and the fertilisation takes place via 'motile sperm' . The female plants produce seeds after fertilisation. These have a fleshy outer layer and fruit like in appearance- they are not a true fruit.
The fleshy layer of the seeds has a distinct smell of rancid butter as it contains butyric acid. This can be unpleasant and lingering if you handle them.
The Ginkgo tree has a unique behaviour during fall. While other trees shed their leaves over a period of days or weeks, Ginkgo leaves fall simultaneously within a few hours, as if planned. They then turn into a yellow gold carpet covering the ground. People call this 'Ginkgo rain'.
Ginkgo in culture
The Ginkgo leaf is a symbol of many things in the far east- they tend to represent endurance and longevity. The trees are also a favourite among bonsai practitioners due to their unique features.
Gingko is a symbol of Tokyo prefecture. It is also a favourite decorative design in fashion and jewellery due to the distinctive leaf pattern.
Ginkgo in Cooking
The inside kernel of the Ginkgo seed is revered as a special ingredient in Eastern cooking. The seed is a key component of Luóhàn zhāi or lo han jai, a traditional Chinese dish served on special occasions and enjoyed by the Buddhist monks as part of their vegetarian diet. The dish is also known as 'Buddha's delight'.
The seeds are supposed to convey health benefits and a long life. Some believe the seeds also have aphrodisiac properties.
In Japan, the seeds form an essential ingredient of Chawanmushi - an egg custard dish that uses Shitake mushrooms, Ginkgo seeds, lily roots and shrimp.
Risks of eating and handling Ginkgo seeds
There are two well reported problems related to Ginkgo seeds. These are mostly related to the outer fleshy coating.
The fleshy layer contains allergenic compounds called ginkgogelic acids ( bilobol and adipostatin A) . These are chemically long chain alkylphenols similar to those found in Poison Ivy. They can cause highly irritant allergic reactions to susceptible individually who handle the seeds. The reaction can cause redness, itchiness and inflammation of the skin known as 'contact dermatitis'. Persons with cashew nut allergy can also share similar reactions to Ginkgo seeds.
It is better to handle the raw seeds with gloves when separating the fleshy outer layer.
Some may get a full blown anaphylactic reaction if they already have nut allergy. Caution is prudent.
MPN Poisoning/ Convulsions
The meat of the seed also contains a compound called Methylpyridoxine ( MPN). Those who consume large numbers of the seeds in a single sitting or over a period of time can experience MPN poisoning. This is particularly true of young children who are more susceptible. Cooking does not destroy this chemical. Symptoms can include rapid loss of consciousness and convulsions.
Thankfully once identified as a cause this can be treated rapidly to reverse the effects.
Ginkgo biloba supplements are made from its leaf. The extract contains flavonoid glycosides (myricetin and quercetin) and terpenoids (ginkgolides, bilobalides) which convey the pharmaceutical benefits.
The key action is believed to be in the brain where the ginsenosides cause reversible effects on a family of enzymes called Monoamine oxidase. These are found all over the body but particularly in the brain. Dysfunction of these enzymes may cause low mood, depression and anxiety.
The ginkgo supplements have been proven correct dysfunctions in monoamine levels by inhibiting this enzyme.
The flavonoids have also been shown to improve blood flow and reduce free radicals that cause ageing and organ deterioration.
Benefits of Ginkgo supplements
The recommended dosage for Ginkgo supplements ranges from 100mg to 240 mg per day ( although manufacturers vary in their suggested dosage). They are mainly marketed as memory and concentration boosters, relief for anxiety and improve blood flow to the brain.
A systematic review of various trials concluded that the supplement improves attention, concentration and memory in some. However, it is not proven to prevent the onset of Alzheimer's or other dementia.
Memory and Concentration
Ginkgo extracts have been shown to improve memory retention and enhance concentration.1 These are mainly thought to be due to the impact of the constituent ginsenosides on neurotransmitters such as Noradrenaline and 5HT. It is also mainly through monoamine oxidase inhibition. A systematic review of various trials have shown improvement of attention concentration and memory compared to placebos2.
It is however not proven to prevent the onset of Alzheimer's or other dementia.
There is evidence in animal trials that Ginkgo reverses brain damage caused by hypoxia or vascular insufficiency.3
Research shows that while taking Ginkgo, patients with intermittent claudication experienced improved walking distance and reduction in calf pain. It has also been shown to help in Raynaud's disease. ( painful reduction in blood flow in hands and feet during cold weather)
Blood flow and Circulation
Emerging evidence also suggests that Ginkgo can help in improving blood circulation to the brain and various organs4. The ginsenosides seem to have an impact on a substance called platelet-activating factor. The latter is responsible for normal clotting processes but is also a key factor in the build up of clots causing arterial blockage. As arterial blockage is the key reason for strokes and heart attacks - there is suggestion that Ginkgo can help in preventing them.
Recent evidence is suggesting a possible use in prevention and treatment of peripheral vascular disease. While taking Ginkgo, patients with intermittent claudication experienced improved walking distance and a reduction in their distressing calf pain 5. Ginkgo can help in improving blood flow to the leg muscles.
Vertigo and Tinnitus
Ginkgo extracts are also marketed for prevention and treatment of vertigo and tinnitus. There is emerging evidence that Ginkgo extracts improve blood flow to the middle ear and thereby help the distressing symptoms of nausea, vertigo and dizziness in disorders such as labyrinthitis.
Research has shown improved microcirculation and vestibular function6. A treatment schedule of 4-6 weeks of Ginkgo extract in recent onset vertigo showed clear improvement of symptoms. There is also some evidence that it could reverse some cochlear damage if it is of vascular origin. The results for treating Tinnitus are mixed - some show clear benefits while others are not conclusive. It is worth a treatment trial.
Energy and Vitality
The build up of free radicals in the body through oxidative damage causes aging and loss of energy. The Ginkgo extracts have some impact on reducing free radical formation and preventing cellular damage. This could lead to slowing of the aging process and higher vitality.
There is anecdotal information from consumers that they feel refreshed and energetic after routine ginkgo supplements. It is unclear if this is an actual or placebo effect.
Other Possible Benefits
Recent studies in animals have also shown the possible use of Ginkgo in reversing cerebral oedema ( following any toxicity). In animal studies has been shown to prevent bronchospasm in allergic shock - leading to improved breathing7.
1.DeFeudis FV. Ginkgo biloba extract (egb 761): pharmacological activities and clinical applications. Paris, Elsevier, Editions Scientifiques, 1991:1187.
2.Kleijnen J, Knipschild P. Ginkgo biloba for cerebral insufficiency. British journal of clinical pharmacology, 1992, 34:352–358.
3.Chatterjee SS. Effects of Ginkgo biloba extract on cerebral metabolic processes. In: Agnoli A et al., eds. Effects of Ginkgo biloba extract on organic cerebral impairment. London, John Libby, 1985:5–14.
4.Auguet M, DeFeudis FV, Clostre F. Effects of Ginkgo biloba on arterial smooth muscle responses to vasoactive stimuli.General pharmacology, 1982, 13:169–171, 225– 230.
5. Blume J et al. Placebokontrollierte Doppelblindstudie zur Wirksamkeit von Ginkgo biloba-Spezialextrakt EGb 761 bei austrainierten Patienten mit Claudicatio intermittens. VASA, 1996, 2:1–11.
6. Haguenauer JP et al. Traitement des troubles de l'equilibre par l'extrait de Ginkgo biloba. Presse medicale, 1986, 15:1569–1572.
7. Desquand S, Vargaftig BB. Interference of the PAF-acether antagonist BN 52021 in bronchopulmonary anaphylaxis. Can a case be made for a role for PAF-acether in bronchopulmonary anaphylaxis in the guinea-pig? In: Braquet P, ed. Ginkgolides, Vol. 1. Barcelona, JR Prous, 1988:271–281.
Ginkgo extracts may cause headaches, allergic reactions and occasional gastrointestinal problems such as diarrhoea or vomiting. These are thankfully not very common.
Ginkgo extracts should always be taken with caution. In case you are on treatment for other conditions, it is essential to consult your clinician and ask about safe intake.
There is no clear safety profile for pregnancy so it is better to avoid it.
Usage in children has not been tested and better avoided.
Patients with clotting or bleeding disorders should consult their doctor before taking Gingko.
With regards to other medications, Ginkgo is better avoided when taking any anticoagulant medications such as Aspirin, Warfarin or clopidogrel. Antidepressants such as the older MAOI inhibitors and SSRIs may interact with Ginkgo.
The table below lists the list of drugs known to have interactions with Gingko.
Possible Drug interactions
Monoamine Oxidase Inhibitors
Fluoxetine ( Prozac)
Warfarin ( Coumadin)
Isocarboxazid ( Marplan)
Citalopram ( Cipramil, Celexa)
Sertraline ( Zoloft)
Clopidogrel ( Plavix)
Selegline ( Emsam)
Paroxetine ( Paxil)
Escitalopram ( Lexapro)
The enduring nature of Ginkgo in the far east lends to a certain mysticism. The quality of the leaf extract has been borne out by the chemistry of the constituent compounds. While there are still some tall claims to its efficacy, these have some underlying scientific basis and the benefits are clearly emerging from clinical trials.
To improve circulation to the brain and limbs, reduce vertigo and tinnitus, improve concentration and attention - Gingko seems to be a safe option. Always buy it from a reputable source and ensure it is a true extract and not some cheap alternative.
It is wise to consult your Doctor if you have other illnesses or are on medications.
Gingko is a fascinating plant and a promising supplement with very few dangers attached to it at the dosages we consume.
© 2014 Mohan Kumar
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