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Ginkgo Flunks its Biggest Clinical Test
1/5/2010
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Presumed herbal brain booster fails to show any benefit in largest, longest trial ever conducted; prior studies provided enough positive evidence to warrant more research
by Craig Weatherby


The leaves of the maidenhair tree, Ginkgo biloba, have been used medicinally in China for thousands of years.


Brain health was among ginkgo’s most common uses, which led to hopes that concentrated extracts of the herb might help deter mental decline.

Millions of Americans take ginkgo pills because they’ve read that it can boost memory, fight off age-related mental fog, and even reduce the risk of dementia disorders… including Alzheimer’s disease.

We cannot yet be certain that ginkgo works as advertised (or implied), given the mixed results from the limited clinical studies conducted to date.

But positive results from some clinical trials have kept consumers buying and provided sufficient evidence to keep researchers interested.

Evidence has been mixed but encouraging
Here’s how the authors of a rigorous evidence review characterized the evidence for ginkgo's brain-boosting powers eight years ago:

“Overall there is promising evidence of improvement in cognition and function associated with Ginkgo” (Birks J et al. 2002).

However, they stressed that the positive ginkgo trials available then were generally small, imperfectly designed, and lacked enough statistical heft to provide proof.

Little had changed when the same evidence-reviewers published a somewhat less hopeful update last year:

“The evidence that Ginkgo biloba has predictable and clinically significant benefit for people with dementia or cognitive impairment is inconsistent and unreliable” (Birks J et al. 2009).

And until last week, the need they identified in 2002
for larger, better-controlled clinical trialsremained unmet.

As if to answer their plea, the Journal of the American Medical Association just published the results of the largest, best-designed clinical trial conducted to date (Snitz BE et al. 2009).

Unfortunately, the outcome was negative, with ginkgo supplements performing no better than placebo pills.

Details of the new ginkgo trial
A team from the University of Pittsburgh recruited 3,069 people between 72 and 96 years of age, with the average age being 79 (Snitz BE et al. 2009).

The participants were randomly assigned to receive either ginkgo pills or placebo pills for an average period of 6.1 years.

The ginkgo group took 120mg of a common extract (EGb 761) made by Germany’s Schwabe Pharmaceuticals.

Their decision to use Schwabe’s EGb 761 ginkgo extract made sense for three reasons:
  • EGb 761 is used in many ginkgo supplements.
  • Most non-EGb 761 ginkgo extracts mimic its chemical profile.
  • EGb 761 is the most widely studied ginkgo extract and the one that has shown the most promise in prior trials.
After six years, the ginkgo group did no better than the placebo group on tests of mental performance, including memory, attention, language, and so-called “executive” (decision-making) brain functions.

As the Pittsburgh group wrote, “In sum, we find no evidence that Ginkgo biloba slows the rate of cognitive decline in older adults” (Snitz BE et al. 2009).

Still, given the large body of previously published positive evidence, the new study should not be viewed as proving ginkgo does nothing to boost aging brains.

But the evidence collected to date suggests that one can’t rely on ginkgo alone to forestall brain aging.

Instead, it makes sense to ensure adequate mental and physical exercise, as well as ample intake of all nutrients, foods, and herbs associated with brain health, including fish-derived omega-3s, curcumin (from turmeric), huperzine-A (from a Chinese medicinal moss), and berries.


Sources
  • Birks J, Grimley EV, Van Dongen M. Ginkgo biloba for cognitive impairment and dementia. Cochrane Database Syst Rev. 2002;(4):CD003120. Review.
  • DeKosky ST, Williamson JD, Fitzpatrick AL, Kronmal RA, Ives DG, Saxton JA, Lopez OL, Burke G, Carlson MC, Fried LP, Kuller LH, Robbins JA, Tracy RP, Woolard NF, Dunn L, Snitz BE, Nahin RL, Furberg CD; Ginkgo Evaluation of Memory (GEM) Study Investigators. Ginkgo biloba for prevention of dementia: a randomized controlled trial. JAMA. 2008 Nov 19;300(19):2253-62. Erratum in: JAMA. 2008 Dec 17;300(23):2730.
  • Kanowski S, Hoerr R. Ginkgo biloba extract EGb 761 in dementia: intent-to-treat analyses of a 24-week, multi-center, double-blind, placebo-controlled, randomized trial. Pharmacopsychiatry. 2003 Nov;36(6):297-303.
  • Le Bars PL, Katz MM, Berman N, Itil TM, Freedman AM, Schatzberg AF. A placebo-controlled, double-blind, randomized trial of an extract of Ginkgo biloba for dementia. North American EGb Study Group. JAMA. 1997 Oct 22-29;278(16):1327-32.
  • Le Bars PL, Kieser M, Itil KZ. A 26-week analysis of a double-blind, placebo-controlled trial of the ginkgo biloba extract EGb 761 in dementia. Dement Geriatr Cogn Disord. 2000 Jul-Aug;11(4):230-7.
  • Mix JA, Crews WD Jr. A double-blind, placebo-controlled, randomized trial of Ginkgo biloba extract EGb 761 in a sample of cognitively intact older adults: neuropsychological findings. Hum Psychopharmacol. 2002 Aug;17(6):267-77.
  • Snitz BE, O'Meara ES, Carlson MC, Arnold AM, Ives DG, Rapp SR, Saxton J, Lopez OL, Dunn LO, Sink KM, DeKosky ST; Ginkgo Evaluation of Memory (GEM) Study Investigators. Ginkgo biloba for preventing cognitive decline in older adults: a randomized trial. JAMA. 2009 Dec 23;302(24):2663-70.
  • Solomon PR, Adams F, Silver A, Zimmer J, DeVeaux R. Ginkgo for memory enhancement: a randomized controlled trial. JAMA. 2002 Aug 21;288(7):835-40.
  • Schneider LS, DeKosky ST, Farlow MR, Tariot PN, Hoerr R, Kieser M. A randomized, double-blind, placebo-controlled trial of two doses of Ginkgo biloba extract in dementia of the Alzheimer's type. Curr Alzheimer Res. 2005 Dec;2(5):541-51.
  • van Dongen M, van Rossum E, Kessels A, Sielhorst H, Knipschild P. Ginkgo for elderly people with dementia and age-associated memory impairment: a randomized clinical trial. J Clin Epidemiol. 2003 Apr;56(4):367-76.

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