Gingko Study Proves Nothing

Drugs and Clinical Trials CategoryBefore you agree with the recent JAMA report that Ginkgo biloba did not prevent dementia, you may want to consider how the study was conducted and whether or not the conclusion researchers made was legitimate.

The study was a large-scale clinical trial on the effectiveness of Ginkgo in reducing the incidence of dementia and Alzheimer’s disease. Six medical centers participated with 3069 volunteers 75 years or older. Of the total number of volunteers, 2587 had no cognitive disorders and 482 had mild cognitive impairment. The volunteers were tracked for a median of 6 years and used either a placebo or 120 mg ginkgo extract twice daily.

The dementia rate was 2.9 per 100 person-years in the placebo group and 3.3 in the Ginkgo group. The researchers concluded that 120 mg of Ginkgo biloba twice daily was not effective in reducing the rate of dementia or Alzheimer’s disease in either those with impaired or normal cognition. The press has interpreted this to mean that Ginkgo biloba is not generally effective.

GingkoDo you believe this conclusion?

“Well, yes, of course,” say a lot of health practitioners. “I won’t recommend it anymore in my practice!”

If you’re in that group of people who say they won’t consider using ginkgo, you may want to think again.

Scientific Oxymoron Unveiled

There’s a huge fallacy that exists in the minds of most people regarding research studies. That fallacy is that you can prove that something is NOT effective.

This is a scientific oxymoron. Science is the systematic observation, measurement and classification of observable phenomenon. The absence of a relationship cannot be observed, classified or measured. Thus, scientific studies can only prove what exists, not what does not exist.

You can’t show or prove safety in a research study. You can’t show or prove something does not have an effect. It’s impossible to qualify and quantify a relationship with something that does not exist. In this case, the absence of an effect of Ginkgo biloba on Alzheimer’s disease.

Pharmaceutical companies use scientific tests to prove that drugs are safe when very often it’s later found that many of them are not. Science has limitations. The ginkgo study is a good example; there are just too many variables that were not measured.

Jumping to Conclusions is Too Easy

There are too many research studies where scientists make blanket statements and generalizations and jump to conclusions without considering all of the data. These blanket statements are all too often the result of poor study design, inappropriate research study methods, lack of planning and possibly even financial backing to prove something for a company.

The ginkgo study superficially demonstrates a lack of effect of ginkgo on cognition; however, as stated above and for the following reasons, this conclusion is flawed:

  • While numerous studies have found that ginkgo improves cognition, the two main causes of Alzheimer’s disease are clearly oxidation and glycation; yet in this study, researchers did not address either.
  • Diet is the major cause of glycation and oxidation. Excess consumption of sugar and polyunsaturated fats maximize the production of advanced glycation endproducts in the body, which drastically increase the potential for Alzheimer’s disease and neurodegeneration. Any study relating to the initiation or progression of Alzheimer’s disease would have to monitor the two most important contributors to its development, glycation and oxidation.
  • The wrong herb was used. A professional herbalist should have been consulted for this study. An herbalist is not a pharmacist and a pharmacist is not an herbalist. Herbalists seldom use a single herb to remediate a health situation or attempt to produce a change in the body.
  • Hundreds of studies on ginkgo are listed, over 2000 total, on PubMed alone. These studies accurately measure both its quantitative and qualitative neuroprotective effects. A large body of evidence has been accumulated on the actions of ginkgo on the brain through population studies, animal studies, human studies with blood indices and tissue studies. It’s well known that Ginkgo increases circulation to specific tissues, including the brain. The median study time was 6 years. Alzheimer’s and dementia take decades to develop. A study with Ginkgo biloba alone would require several decades.
  • The synergistic effect of a group of herbs taken together can be expected to produce a greater effect than the benefit of each herb taken by itself. Successful treatment will not come from any one substance.
  • The bottom line is that no responsible herbalist would send someone home with Ginkgo biloba and tell them that Ginkgo was all that was needed to prevent neurodegeneration.
  • Any good researcher would have looked at the available scientific evidence and found that alpha-lipoic acid, resveratrol, numerous polyphenols, carnosine, and benfotiamine have profound effects on the processes of oxidation and glycation and designed the study based on that evidence.

The JAMA study was poorly designed. It was not conducted for an adequate length of time. The conclusions of the study falsely suggest that herbal treatment of dementia and Alzheimer’s does not work.

One of President Elect Obama’s new goals is to do a line item review of what is being funded by the government. Why not start with faulty, inconclusive medical research that proves nothing?

More on preventing and treating Alzheimer’s disease successfully next time…


S. T. DeKosky, J. D. Williamson, A. L. Fitzpatrick, R. A. Kronmal, D. G. Ives, J. A. Saxton, O. L. Lopez, G. Burke, M. C. Carlson, L. P. Fried, L. H. Kuller, J. A. Robbins, R. P. Tracy, N. F. Woolard, L. Dunn, B. E. Snitz, R. L. Nahin, C. D. Furberg (2008). Ginkgo biloba for Prevention of Dementia: A Randomized Controlled Trial JAMA: The Journal of the American Medical Association, 300 (19), 2253-2262 DOI: 10.1001/jama.2008.683

  • You are quite correct to say that science cannot prove a negative. All the JAMA study showed was that when a particular preparation of Gingko biloba was given to this group of men and women for this period of time it was no better than a placebo in preventing or delaying the onset of dementia.

    The trial appeared to be well designed. Certainly as well — or better — designed as many of the studies you cite in support of the use of such herbal products.

    Finally, the study does not “falsely suggest that herbal treatments for Alzheimer’s and dementia do not work.”

    This is what the study authors said:

    “In summary, in this randomized clinical trial in 3069 older adults with normal cognitive function or mild deficits, G biloba showed no benefit for reducing all-cause dementia or dementia of the Alzheimer type. A central issue in testing of complementary and alternative medications is the formulation of the compounds. This study used a requisite standardized formulation of G biloba extract with specified amounts of the active ingredients in a dosage based on the highest doses used and reported in the literature. The extract we tested is among the best characterized and is the one for which the most efficacy data are available. Thus, we believe that the results are applicable to other G biloba extracts. Based on the results of this trial, G biloba cannot be recommended for the purpose of preventing dementia.”

  • Ian Kemmish

    “The synergistic effect of a group of herbs taken together can be expected to produce a greater effect than the benefit of each herb taken by itself. ”

    “Expected”? By whom? Certainly not by anyone with pretensions to either call themselves a scientist or to criticise other scientists. Can you even cogently propose a mechanism by which such a counterintuitive result might arise?

  • Jacob Keum

    I see lots of patients MCI and other cognitive impairments..
    and, Gingko is one of few agents i recommend….
    One of my staff physicians brought this article to my attention and initially I was reading it incorrectly.
    Dr Dekosky study is aimed in preventing dementia…more specifically Alzheimer’s
    But there are thousands of articles published in the efficacy in cognitive improvement of Gingko which is rather different proponent than the actual preventing progression…Actually they are totally different topics.

    So I have not thrown Gingko out of my recommended herbs among many other agents with neuroprotective effect.. Aricept and other medications can claim to have neuroprotective effect….
    They are more of enzyme blockers.

    I do thank your valuable thoughts on your opinion…
    Plus, I am not sure the type of other financial interests driving research in general specially if
    Pharmaceutical market share is concerned…

  • elfman

    “The absence of a relationship cannot be observed”

    The author of this nonsense is seriously confused. Of course the absence of a relationship can be observed. It’s the foundation of the scientific method. Make an assertion and dare the world to disprove it. Claim that pressing a horn causes a honk, and let the world try to disprove it. Then, if several good studies like this one show no relationship, “the absence of a relationship” is presumed.

Donna Schwontkowski, MS, DC

Donna Schwontkowski, MS, DC, has been a professional writer for the last 20 years and authored the book "Million Dollar Memory for Names & Faces" released in 2006. She also has been the editor of a local health and fitness magazine in California for the past 12 years. She holds a doctorate in chiropractic medicine, a master's and bachelor's in nutrition, and a master's in herbology.
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