• Quote of the Day
    "Our job in this lifetime is not to shape ourselves into some ideal we imagine we ought to be,
    but to find out who we already are and become it."
    Steven Pressfield, posted by David Baxter

David Baxter

Mar 26, 2004
Gingko Biloba And Memory
By Dr. Steven Novella
Mon, Mar 3 2008

Gingko biloba is a plant that has long been used as a Chinese herbal remedy in a standard extract. Since the deregulation of the supplement industry in the US in 1994 gingko has become one of the more popular herbal supplements sold in the US (annual sales for 1997 were estimated at $240 million, and have only increased since). The primary claim for gingko is that it improves memory and cognitive function, and may even stave off the onset of Alzheimer?s dementia. Other claims include that it is useful for headache, depression, and tinitus (ringing in the ears).

The problem with the current regulation is that it essentially allows companies to make claims without having to provide evidence to back up those claims, therefore the marketing is ahead of the research. This has been true for gingko as well - is has been marketed as a memory aid for years and only later has the research started coming in.

The latest issue of Neurology online contains a double-blind placebo controlled study of gingko biloba extract in a health elderly population (118 subjects) which was followed for 42 months. The study is essentially negative - not supporting the use of gingko in preventing memory decline in the elderly - but there are some complexities to the interpretation of the study.

The primary outcome was an intention to treat analysis - that means the net effect was measure without taking into account whether or not the subject actually took the treatment or placebo. This type of analysis is useful if the question is whether or not it is useful to prescribe a treatment. If a treatment works, but no one can take it because it is too complex, inconvenient, or has too many side effects, then it is not a very practical treatment. But if your question is whether or not a specific treatment works (regardless of whether it is practical) then you have to account for compliance.

In this study the primary outcome was intention to treat and it was completely negative - no benefit from gingko in preventing progression to dementia. The authors did a secondary analysis, however, where they accounted for compliance and with this analysis two effects emerged: a mild protective effect from gingko, and an increase in strokes and transient ischemic attacks (TIA?s). How should we interpret this?

First - primary outcomes in a study always have more weight, for that is how the study was designed and the question that was asked prior to the data being collected. Secondary analysis is always suspect - it usually involves additional statistical complexity, may involve an analysis of only a subset of the subjects, and also may involve a re-analysis of data after it is collected, which opens the door for bias and further statistical anomalies.

Also, this study was designed as a pilot study, which means it was low power (118 subjects is a very small number for such a study). This means that the results are not very reliable, but were intended to help design a larger more definitive trial. For example, the authors used the data from this trial to calculate that a follow up trial would need at least 300 subjects to have an 80% chance of detecting an effect (depending on certain variables it may also require as many as 2800 subjects). This study also indicates that any follow up study should closely track strokes and TIA?s as a possible adverse side effect.

My opinion is that the bottom line from this study is that it does not tell us anything definitive, but that it argues against any clinically significant effect from gingko, but of course does not rule out a small effect. The increased risk of stroke and TIA is likely not real, but it could be. Gingko is known to be a mild blood thinner, and should not be taken with aspirin or coumadin, which are also blood thinners. There is concern that gingko increases the risk of bleeding, but usually (if anything) a blood thinning effect is associated with a decreased risk of non-bleeding strokes. So either this side effect was spurious or the effects of gingko on blood clotting and platelet function are more complex than we currently know.

To put this one small study into the broader context of the clinical literature, a recent Cochrane review of clinical trials of gingko and memory concluded:

The evidence that Ginkgo has predictable and clinically significant benefit for people with dementia or cognitive impairment is inconsistent and unconvincing.​
That basically means that the evidence suggests gingko does not work for memory, despite the hundreds of millions of dollars of sales based upon that claim. This new study does not alter this conclusion.

The other context that is critical to thinking about gingko and it?s clinical utility is that all of this discussion of clinical trials, possible medical benefits, and concerns over side effects is identical to the type of discussion we would have about any drug. There is a good reason for that - gingko biloba extract is a drug or combination of drugs and it should be treated as such. The medical and research community treats it exactly like a drug - with pharmacological effects that can be studied using standard techniques, active ingredients, drug-drug interactions, and potential clinical effects and side effects. Why then is it regulated as if it were a dietary supplement?

Our experience with gingko also shows that centuries of traditional use is not a good predictor of clinical efficacy. Such a history therefore does not obviate the need to conduct proper clinical trials. Gingko may, in fact, be causing more harm than good (or harm without any good).

The only rational conclusion is that drugs should be regulated as drugs.


Oct 30, 2008
Ginkgo Biloba Doesn't Slow Mental Decline

Ginkgo Biloba Doesn't Slow Mental Decline
By Daniel J. DeNoon, WebMD Health News
Dec. 29, 2009

Popular Supplement Fails to Slow Mental Decline in 6-Year Study

The hot-selling herbal supplement ginkgo biloba doesn't slow age-related mental decline, a six-year clinical study shows.

The study has already shown that ginkgo does not prevent dementia or Alzheimer's disease in the elderly.

Now study leader Steven T. DeKosky, MD, and colleagues have sifted through the data to look for some sign that ginkgo might slow mental decline in healthy, aging individuals -- or, perhaps, in those already showing the first signs of cognitive impairment.

No such sign was found.

"Compared with placebo, the use of Ginkgo biloba, 120 mg twice daily, did not result in less cognitive decline in older adults with normal cognition or with mild cognitive impairment," the researchers conclude.

The problem wasn't potency. The study used the standardized ginkgo extract from Schwabe Pharmaceuticals that is regulated and sold as a medication in Germany.

And the problem wasn't rigorous testing. Twice a year, the 72- to 96-year-old study participants received a battery of tests that measured various aspects of mental function, including memory, attention, visuospatial abilities, language, and executive function.

Regardless of which mental function was measured, the tests show gingko doesn't help slow cognitive decline.

The findings echo those of a 2009 Cochrane Review of ginkgo studies that identified no cognitive benefit from the supplement.

The Council for Responsible Nutrition, a group representing the supplement industry, suggests that the DeKosky study "should not be viewed as the final work" on ginkgo.

In a written statement, Douglas MacKay, ND, CRN vice president for scientific and regulatory affairs, notes that cognitive decline has many causes and that neither ginkgo nor any other single treatment is a magic bullet.

"As a former practicing licensed naturopathic doctor, I have had the benefit of working with patients and have seen first-hand how Ginkgo biloba can be effective in improving cognitive function," MacKay says. "I would continue to recommend Ginkgo biloba to older adults as a safe, effective option for supporting cognitive health and would encourage consumers to talk to their own healthcare professional about what is right for them."

DeKosky and colleagues report their findings in the Dec. 23/30 issue of The Journal of the American Medical Association.

{NicNak: although this article is not promoting the use of Ginko Biloba, from the various articles I have read on Ginkgo Biloba, it does seem to interact with a lot of the medications we could be taking. Always remember before taking any supplement of any kind to speak to your prescribing doctor or pharmacist}
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David Baxter

Mar 26, 2004
I find it remarkable, to say the least, that despite repeated demonstrations that ginko biloba provides no benefits, "naturopathic" doctors continue to promote its use, clearly preferring to base their practices on observational and anecdotal "evidence" rather than the data from controlled research studies. It's a testament to the persistence of naturopathy and its stubborn resistance to science.


MVP, Forum Supporter
Jul 14, 2006
I am really glad you posted this, you just saved me some money. I have been thinking about trying this, thinking there might be a chance it would help my memory and concentration. Isn't it ironic that I kept forgetting to pick it up :lol:

Yes, it reminds me of that book on procrastination that I have been meaning to buy but I haven't gotten around to it yet.

Sorry, blame my bad prairie humour, or you can also blame the New Years Punch. Hope everyone is having a safe and happy holiday.

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