|Ginkgo and Alzheimer's Disease|
The herb industry and the supplement manufacturers are making some dramatic claims for Ginkgo (Ginkgo biloba) in the treatment of dementia and Alzheimer's disease. It is worth reviewing some of the research that has been done. What follows is taken papers in the book:
Fünfgeld, E.W. (Ed.). Rökan, Ginkgo biloba. Recent Results in Pharmacology and Clinic. Springer-Verlag, Berlin 1988
Alzheimer's disease is a neurological disorder of the brain which, whilst once thought rare, is now considered the largest single cause of senile dementia. Senile dementia, a condition of irreversible mental deterioration, always involves memory loss and is almost always accompanied by numerous other difficulties in mental function. Current studies suggest that 1% of the population in developed countries with a large proportion of elderly people is affected.
The brain develops `neuritic plaques', which consist of degenerating nerve terminals and other materials associated with the appearance of fibrous structures, called the neurofibrillary tangle, within nerve cells. One proposed cause of the growths has been the decline observed in the brain's production of acetyl-choline. Recent studies show that the diseased brain also metabolizes glucose at diminished levels and that abnormally high levels of aluminum and silicon occur. No allopathic cure exists for the disease.
Attention is being given to Ginkgo leaf (Ginkgo biloba) in the treatment of such problems, with much of the clinical and pharmacological research coming from France. The herb has a classical reputation as an anti-microbial and anti-tubercular agent.1However new research has shown a profound activity on brain function and cerebral circulation. Clinically it seems to be effective in patients with vascular disorders, in all types of dementia and even in patients suffering from cognitive disorders secondary to depression, because of its beneficial effects on mood.
Of special concern are people who are just beginning to experience deterioration in their cognitive function. Gingko might delay deterioration and enable such people to maintain a normal life. The earlier treatment begins, the better the prognosis, especially in Alzheimer's. Even in advanced cases, however, improvement may begin almost immediately and continues over many months. This property is important because every cell of the body will suffer when there is an inadequate supply of blood, leading to lack of energy, susceptibility to infection, decreased mental and physical function etc.. Dementia in the elderly usually related to inadequate circulation.
Laboratory studies of Gingko show it to reduce vascular, tissue and metabolic disturbances as well as their neurological and behavioral consequences.Several membrane mechanisms seem to be involved including protection of the membrane ultra-structure against free radicals. This activity has exciting implications with the new insights about aging and free radicals.
The uniqueness of the pharmacological properties of Gingko lies in its focusing its effects on tissue that is experiencing oxygen lack, by increasing the flow of blood into is chaemic tissue.2It may help by:
- raising levels of glucose and ATP in the cell, thus maintain energy levels.
- stabilizing cellular membranes including the blood brain barrier, thus reducing any cerebral edema and hypertension.
- slowing the onset of dementia resulting from sclerosis of cerebral arteries
- ameliorating the effects of progressive cerebral circulatory insufficiency due to age
- decreasing the consumption of insulin, thus of potential use in diabetic angiopathy, especially as it has minimal impact on glucose metabolism, making it appropriate for diabetics, who generally suffer from insufficient circulation.
- being hypotensive and peripherally vaso-dilating, offering a treatment for hypertension, as an aid in recovery from coronary thrombosis, and intermittentclaudication.
Ginkgo has marked effects on neurophysiology, but it also seems to concentrate in the vascular and endocrine systems that strongly affect the function of the nervous system. This especially so in the adrenal gland, responsible for producing dopamine, epinephrine and norepinephrine as well as intermediary products required in the formation, activity and metabolism of other neurotransmitters. Ginkgo is also, through its affects on blood flow, able to improve the availability of acetylcholine, another important neurotransmitter. These effects include:
- stimulation of the synthesis of important neurotransmitters, thus increasing the capacity for physical activity, both voluntary and involuntary functioning(e.g. digestion, blood pressure regulation, hormone secretion, blood sugar regulation).
- increasing the flow of blood to the brain & stimulating the growth of receptor sites, leading to increased cerebral capacity, manifested by improved memory and reasoning power, improved mood, improved reaction time, alertness and speech.
- inhibiting the synaptic breakdown of neurotransmitters and so increasing their availability during neural stimulation. This will increase the efficiency of the nervous system, and thus improve mood, memory and self- mastery.
It is prescribed in orthodox medicine for a number of neurological and behavioral disorders of the elderly, in peripheral vascular deficiency and in some functional disorders of the ear, nose, throat and eye. Numerous controlled clinical trials have been conducted to justify this use and these excellent clinical findings are in agreement with pharmacological data currently available. Experimentally, Gingko extract is active on cerebral circulation, on neuronal metabolism threatened by oxygen lack, on neurotransmission and on neuronemembrane lesions caused by free oxygenated radicals.3Improvement of the functioning of the auditory nerve of the ear is discussed further in the section on Tinnitus.4
The herb offers much hope as a treatment in all types of dementia, and even in patients suffering from cognitive disorders secondary to depression, because of its beneficial effects on mood. Of special concern are people who are just beginning to experience deterioration in their cognitive function.Ginkgo might delay deterioration and enable these subjects to maintain a normal life. Anyone can benefit from the use of Ginkgo, whether they are already experiencing the effects of aging on mental function, or just approaching that point. In addition, the herb is quite safe even in doses many times higher than those usually recommended.5
From the experimental and clinical findings it appears that the herb may act on a number of major elements in the causation of both Alzheimer's and dementia. Current ideas about causes of Alzheimer's include (amongst other things) free radical damage, vascular insufficiency, is chemia, cholinergic and noradrenergic dysfunction. Clinically Ginkgo is active on circulatory functions, on neuronal and metabolic consequences of is chemia and hypoxia, on neurotransmission, and on membrane resistance to free radical damage. All of clinical studies so far confirm that the diverse physiological effects of Ginkgo lead to positive effects on behavior, sense of well-being, decreased hospitalization and capacity for self-sufficiency.
Free radicals have been implicated in the aging process and degenerative disease. The flavonoids of ginkgo, including quercet in, are extremely potent oxygen scavengers. Possessing a particular affinity for the central nervous system as well as the adrenal and thyroid glands, the herb is ideal for protecting the heart, blood vessels, and brain against the destructive impact of free radicals.
- In one in vitro study it destroyed free radicals, blocking their formation and inhibiting membrane lipid peroxidation, a destructive effect for which free radicals are partly responsible. The herb also stimulates the biosynthesis of prostanoids, vaso-dilators having a hypotensive effect.
- One of the side-effects of diabetes in rats is the gradual impairment of eye sight, thought to be due to free oxygenated radicals damaging the retina. Ginkgo significantly prevented the onset and severity of this damage.
- Ginkgo improved visual acuity in patients suffering from senile macular degeneration, a condition that involves free radicals damage.
- A protective effect against argon laser induced damage of retinal cells was found. Pretreatment with Ginkgo, by capturing free radicals, prevented significant tissue damage.
Clearly Ginkgo could be important herbal contribution to the treatment and prevention of Alzheimer's disease. The French workers suggest that this herb fulfills the conditions laid down by the W.H.O. concerning the development of drugs that are both effective and safe against cerebral aging.6Itwould seem that yet again the plant kingdom is truly supplying our needs.
1 Bensky & Gamble: Chinese Herbal Medicine , 1986, Eastland Press
2 Clostre F: From the body to the cell membrane: thedifferent levels of pharmacological action of Ginkgo biloba extract.
PRESSE MED 1986 Sep 25; 15(31):1529-38
3 Gautherie et.al.: Vasodilator effect of Gingko bilobaextract determined by skin thermometry and thermography
THERAPIE (Sep-Oct 72) 27(5):881-92
4 Stange et.al.: Adaptational behaviour of peripheral and centralacoustic responsesin guinea pigs under the influence of various fractionsof an extract from Gingko biloba. ARZNEIM FORSCH (1976) 26(3):367-74
5 Warburton DM: Clinical psychopharmacology of Ginkgo bilobaextract PRESSE MED 1986 Sep 25; 15(31):1595-604
6 Allard M: Treatment of the disorders of aging with Ginkgobiloba extract. From pharmacology to clinical medicine.
PRESSE MED 1986 Sep 25; 15(31):1540-5
About The Author
Whilst working in conservation and lecturing in ecology and the eco-crisis for the University of Wales, David Hoffman became convinced that to heal the world, to embrace planetary wholeness and responsibility for it with hope, he as an individual had to be whole within himself....more