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Ginkgo and Biloba Memory

Ginkgo is a prized and commonplace herb in alternative medicine. It has been recommended for treating a variety of medical conditions including memory loss. Is ginkgo any good at improving memory? There are studies that say yes and no. Read on to find out the conclusion after weighing the evidences.
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What is Ginkgo?

Ginkgo is the name given to the herbal extract obtained from the Maidenhair Tree which is also known as Ginkgo biloba. The maidenhair tree is an ancient tree whose parts have various use in traditional medicine and as food.

The leaves of ginkgo provides the most medicinal benefits of the various parts of the tree.

Key ingredients found in ginkgo extract include terpenoids such as ginkgolides and bilobalides as well as flavonoid glycosides. These ginkgo phytochemicals are known monoamine oxidase inhibitors. They also block the reuptake of neurotransmitters such as dopamine, serotonin and norepinephrine.

The effect of ginkgo on norepinephrine reuptake is believed to be responsible for the herb’s effects on cognition.

Ginkgo is a nootropic agent. This means that it is useful for enhancing memory and concentration. However, ginkgo does not appear to improve dementia or cognitive decline in Alzheimer’s disease.

The 3 proven effects that ginkgo extracts have on the body include:

  • Increasing blood flow (especially microcirculation in the capillaries) to different organs and tissues
  • Antioxidant properties demonstrated by prevention of oxidative damage through free radical neutralization
  • Preventing platelet aggregation and blood clotting

Ginkgo is not recommended for people with blood circulation disorders (because of its effects on blood flow and blood clotting) and those placed on certain antidepressants (because of its effects on monoamine neurotransmitters such as serotonin). The herb should also be avoided by pregnant women.

The anticoagulant properties of gingko also means that it should be avoided by people placed on blood thinners such as warfarin.

People who are allergic to poison ivy, cashews and mangoes should avoid ginkgo supplements because the ginkgolic acid in the herb is related to the allergenic phytochemicals in these other plants.

Common side effects of ginkgo extracts include headaches, nausea, vomiting, diarrhea, gastrointestinal discomfort, dizziness, heart palpitations and an increased risk of bleeding.

The usefulness of ginkgo extract in the restoration of cognitive function especially memory loss caused by dementia has been well studied. Over the years, the studies done on the subject have produced mixed results with some concluding there are benefits while others proving there is none.

Ginkgo and Memory: The Positive Results

In a 2001 study published in The International Journal of Neuropyschopharmacology, the researchers administered ginkgo extract to 61 healthy study participants. The study was randomized, placebo-controlled and double-blinded to eliminate bias.

After 30 days of supplementation with ginkgo, the study subjects were given the same set of standard neuropsychological tests that they took at the beginning of the trial.

The result of this trial showed that the ginkgo extract administered produced statistically significant improvement in working memory, information processing and decision making.

A 2005 study published in the Pharmacological Reports of the Institute of Pharmacology of the Polish Academy of Sciences investigated the benefits of ginkgo in relieving stress-induced memory loss in rats.

The researchers caused post-stress memory impairment by inducing chronic stress for 2 days 21 hours or with corticosterone injections.

The rats who received ginkgo extract recovered from this chronic stress and scored highest in spatial and non-spatial memory tests. In addition, the administration of 100 mg/kg of ginkgo extract before stressing the rats normalized neutralized the effects of stress on memory and cognitive functions.

Ginkgo and Memory: The Case against Ginkgo

A 2002 study published in the Journal of the American Medical Association tested the efficacy of over-the-counter ginkgo supplements for the enhancement of memory.

The actual study took 6 weeks and recruited 230 healthy participants (98 men and 132 women) over the age of 60. By randomizing who gets what, each participant either got ginkgo pills or a placebo that appeared and tasted similar. The ones who got ginkgo took it according to the manufacturer’s recommendation (40 mg taken 3 times daily).

At the end of the study, the participants took standardized neuropsychological tests to access improvements in verbal and non-verbal learning as well as memory, attention and mental focus.

The results showed that of the 88% of the participants who completed the study, there was no significance difference between the ginkgo group and the placebo group on any count of cognitive function including memory.

Not only the standard tests, but also subjective assessment by the participants’ friends and families revealed no difference between the drug group and the placebo group.

In a 2004 study published in the journal, Psychopharmacology, the memory-enhancing promise of ginkgo and ginseng was accessed in a group of 126 healthy participants.

This study was a subset of the larger Betula Prospective Cohort Study (3500 participants) done to understand the effects of medicinal agents on memory, health and aging.

A statistical analysis of the study showed that neither ginkgo nor ginseng improved scores in the eight memory tests done for those taking them compared to those who did not. The study concluded that there was no quantifiable benefit from long-term supplement of ginkgo or ginseng on memory performance.

A 2000 paper published in the Journal of American Geriatrics Society evaluated the possible efficacy, dose-dependence and longevity of ginkgo extracts on dementia caused by aging.

The randomized, placebo-controlled, double-blind, parallel, multicenter study recruited 214 residents of 39 old peoples’ homes.

The study took 24 weeks during which each participant was given one of placebo, the usual dose of ginkgo extract (160 mg daily) or a higher dose (240 mg daily). 12 weeks into the trial, the participants were assessed and drug choice randomized again.

The key tests in the assessment measured include verbal learning, memory span, memory status, geriatric symptoms of cognitive decline, depression, self-perception and self-reported behavior.

The results of this study showed that ginkgo supplementation did not improve the scores on any of these tests compared to placebo supplementation.

The Ginkgo Evaluation of Memory (GEM) Study

This is the definitive study on the subject of ginkgo and memory.

GEM took 8 years, was conducted in 4 clinical sites and was sponsored by NCCAM (National Center for Complementary and Alternative Medicine). The results published in the December 2009 issue of Journal of the American Medical Association.

GEM assessed the effect of ginkgo extracts on cognitive decline, blood pressure, the cardiovascular system and cancer.

This study recruited over 3000 participants aged between 72 and 96 years. At the start of the study, each participant either hand normal cognition or mild cognitive impairment. Although the study took place between 2000 and 2008, the mean follow-up period was 6.1 years.

During the trial, each participant either received 240 mg of ginkgo (120 mg given twice daily) or an identical placebo. Throughout the duration of the trial, the participants were periodically given cognitive tests to access general cognitive decline especially as it affects memory, mental focus, visual-spatial coordination, and language.

The results of GEM showed that ginkgo did not reduce cognitive decline in any way.

Compared to the group receiving placebo, the ginkgo group experienced the same rate of cognitive decline. Even after correcting for age, sex, race, education and initial cognitive status, ginkgo did not produce a better outcome than placebo.

In Conclusion

The GEM study and also the Cochrane review, done in 2009 to assess the benefits of ginkgo on dementia and cognitive decline from available studies done on the subject, agree that ginkgo has no statistical significant effect on memory and memory loss.

Even though early studies showed that there might be a modest benefit to taking ginkgo to enhance memory, those studies have largely been rendered irrelevant by the newer, larger studies and the Cochrane review.

It seemed that ginkgo is a victim of “doctrine of signatures” in this regard.

Proponents of this doctrine would believe that since ginkgo is the oldest living tree species and regarded traditionally as a symbol of ancient wisdom, it must have the ability to improve age-related cognitive decline including memory loss.

However, quite a large body of clinical studies have proven this cute, sentimental theory wrong.

In other respects, ginkgo works. It improves blood circulation; it has antioxidant properties and it is a powerful anticoagulant. But a memory enhancer, it is not.

Sources


http://ukpmc.ac.uk/abstract/MED/11037003

http://jama.jamanetwork.com/article.aspx?articleid=195207

http://www.springerlink.com/content/lheb14v2aj1uy2ah/

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