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Herbal Science Organization Clarifies New Ginkgo Study
(Austin, TX) December 28, 2009. New research findings published this week on a standardized Ginkgo biloba extract are very limited and the public should focus on the well-documented cognitive and cardiovascular benefits of ginkgo, said the American Botanical Council (ABC), an independent nonprofit research and education organization.
A new study of previously published data being published in this week’s issue of the Journal of the American Medical Association (JAMA) has reported that a leading ginkgo extract did not reduce the decline in cognitive impairment in older adults.1,2
“There are many significant limitations of this study”, said Mark Blumenthal, ABC founder and executive director.
First, the data being published this week are drawn from a previous clinical trial which was not designed to determine the decline in cognition.3 Second, about 40% of the subjects dropped out over the 6-year duration of the trial; the statistics reported in the study include the dropouts for which no final data are available. Further, the subjects in the study were not monitored for certain cognitive parameters until several years after the trial began, creating difficulty in determining accurately whether they experienced a decline in cognition or not. Also, the age of the subjects is quite advanced, at an average of 79 years at the beginning of the trial. This age group is not typical of the age of both healthy people and those with mild cognitive impairment who use ginkgo for improving mental performance.
Further, ABC noted that another weakness of this trial is the lack of an active control, i.e., a potential third arm of the trial (i.e., besides the patients on ginkgo or placebo) in which patients would have used a pharmaceutical medication with presumed efficacy, to determine to what extent the particular population being tested would respond. This was not possible for this trial since no conventional pharmaceutical drug has ever demonstrated the ability to prevent the onset of dementia or diminish its progression.
ABC also stated that several recent publications have demonstrated an improvement in cognitive performance in subjects using the same German gingko extract.4,5,6
The new publication, by Beth E. Snits, Ph.D., a neuropsychologist associated with the University of Pittsburgh, and other colleagues, analyzed outcomes from the Ginkgo Evaluation of Memory study (GEM, published in 2008 in JAMA) to determine if ginkgo extract slowed cognitive decline in older adults who had either normal cognition or mild cognitive impairment at the beginning of the study. 3
The GEM study previously found that ginkgo extract was not effective in reducing the incidence of Alzheimer dementia or dementia overall. This large, randomized, double-blind, placebo-controlled, multi-centered clinical trial included 3,069 community-dwelling subjects (aged 72 to 96 years) who received either a dose of 120 mg of ginkgo extract twice daily or an identical-appearing placebo. The trial was conducted at 6 academic medical centers in the United States between 2000 and 2008, with a median follow-up of 6.1 years. Change in cognitive function was evaluated by various tests and measures.
ABC emphasized that the original GEM trial was designed to determine whether taking ginkgo would prevent the onset of dementia. What this new publication has done is attempted to analyze the possible decline in levels of cognitive function – not a primary outcome measure of the GEM study.
“This trial is not conclusive nor should it in any way detract from ginkgo’s reputation as a useful dietary supplement to help support and improve cognitive function and enhance peripheral circulation – conditions for which it has been reported to be effective in numerous clinical trials,” reminded Blumenthal.
At least 16 controlled clinical trials have evaluated various ginkgo extracts for healthy, non-cognitively impaired adults. A systematic review has shown that in 11 of these trials, the ginkgo increased short-term memory, concentration and time to process mental tasks.7
“The results of this new trial must be viewed in proper perspective,” noted Blumenthal. “There is a vast body of pharmacological and clinical research supporting numerous health benefits for ginkgo extracts, particularly for improving various symptoms and conditions associated with declining cognitive performance and poor circulation.”
ABC also emphasized that this publication, and the one published in 2008 on which it is based, both underscore the relative safety of ginkgo extract: the amount of adverse events were basically the same in both the ginkgo and placebo groups, particularly no serious adverse effects, e.g. no statistically significant incidence of coronary heart disease, stroke of any type, and major bleeding.
The trial utilized EGb 761®, the world’s most clinically tested ginkgo extract, produced by W. Schwabe Pharmaceuticals in Karlsruhe, Germany.
About Ginkgo Extract
Ginkgo (Ginkgo biloba) is the world’s oldest living tree, dating back about 250 million years. Ginkgo leaves have been used in traditional Chinese medicine for about 500 years. For about the past 30 years the leaves of ginkgo have been made into a highly concentrated (50:1) extract, chemically standardized to compounds unique to ginkgo (ginkgolides and bilobalide) as well as other compounds. The leading German ginkgo extract has been subjected to a vast range of clinical trials documenting its ability to improve peripheral circulation and cognitive function, particularly in patients with early stages of mild cognitive impairment, senile dementia, Alzheimer’s disease, and memory loss. Clinical trials also support the use of ginkgo extract in assisting elderly patients in walking longer distances without leg pain (peripheral arterial occlusive disease, also known as intermittent claudication). Standardized ginkgo extracts are approved for use as medicines in Germany and numerous other countries.
About the American Botanical Council
Founded in 1988 the American Botanical Council is a leading international nonprofit organization addressing research and educational issues regarding herbs and medicinal plants. ABC’s members include academic researchers and educators, universities and libraries, health professionals and medical institutions, botanical gardens and arboreta, government agencies, members of the herb, dietary supplement, cosmetic, and pharmaceutical industries, journalists, consumers, and other interested parties from over 70 countries. The organization occupies a historic 2.5-acre site in Austin, Texas where it publishes the quarterly journal HerbalGram, the monthly e-publication HerbalEGram, HerbClips (over 4000 summaries of scientific and clinical publications), reference books, and other educational materials. ABC also hosts HerbMedPro, a powerful herbal database, covering scientific and clinical publications on more than 220 herbs.
ABC is tax-exempt under section 501(c) (3) of the IRS Code. Information: Contact ABC at P.O. Box 144345, Austin, TX 78714-4345, Phone: 512-926-4900. Website: http://www.herbalgram.org/.
1. Snitz BE, O'Meara ES, Carlson MC, Arnold A, Ives DG, Rapp SR, Saxton J, Lopez OL, Dunn LO, Sink K, DeKosky ST. Does Ginkgo biloba slow cognitive decline in older adults? JAMA Dec 23/30, 2009.
2. American Medical Association. Ginkgo Biloba Does Not Appear to Slow Rate of Cognitive Decline. [press release]. Chicago, IL: Dec. 23, 2009.
3. DeKosky ST, Williamson JD, Fitzpatrick AL, et al. Ginkgo biloba for prevention of dementia: a randomized controlled trial.[see comment]. JAMA. Nov 19 2008;300(19):2253-2262.
4. QWiG Institut für Qualität und Wirtschaftlichkeit im Gesundheitswesen. IQWiG Reports - Commission No. A05-19B. Ginkgo in Alzheimer's disease. Executive Summary. Cologne: IQWiG, 2008.
5. Kaschel R. Ginkgo biloba: specificity of neuropsychological improvement – a selective review in search of differential effects. Human Psychopharmacology: Clinical and Experimental 2009;24:345-370.
6. Kasper S, Schubert H. Ginkgo-Spezialextrakt EGb 761® in der Behandlung der Demenz: Evidenz für Wirksamkeit und Verträglichkeit. [Ginkgo biloba extract EGb 761® in the treatment of dementia: evidence of efficacy and tolerability.] Fortschritte Neurologie Psychiatrie 2009;77:494-506.
7. Crews W, Harrison DW, Griggin ML, Falwell KD, Crist T, Longest L, Hehemann L, Rey ST. The neuropsychological efficacy of ginkgo preparations in healthy and cognitively intact adults; A comprehensive review. HerbalGram 2005;67:42-62.