reviewed by X. Li, Ph. D.
(credential)
Then it comes with another large trial2. This trial was published in JAMA,
the Journal of the American Medical Association, a high profile medical journal. The study hit the news headline
for its claim that ginkgo offers no benefits for memory (news)
that is contradictory to the other studies described above.
Similarly to the previous trial1, in this trial2, 230 volunteers who had no memory impairment
and were of both sexes and of at least 60 years old were enrolled.
The trial was also placebo-controlled, double-blind, and randomized.
In the trial, the participants received either 120 mg of the standard ginkgo biloba extract
or placebo daily for 6 weeks. As outcome measures,
14 standardized neuropsychological tests were taken at the start and the end of the trial.
These measures test verbal and nonverbal learning and memory, attention and concentration, naming
and expressive language.
The participants themselves and their close contacts were also asked to rate any change in memory.
After statistical analysis, the authors found none of the tests showed any significant difference
between volunteers who took ginkgo and placebo. Moreover, similar numbers of volunteers felt that
they have improved mental performance. Therefore, it was concluded that under the trial setup
no evidence was found to support a role of ginkgo in enhancing memory in healthy old adults2,
which is contradictory to the other studies.
The trial has drawn some criticisms and debates from other researchers. Several issues were raised
concerning the quality of the trial design and analysis. For example, the authors did not assay to
confirm the content of the standardized ginkgo biloba extract they bought from market for
use in their trial. This reviewer also noticed that the duration of the trial lasted for over 2 years,
it was not clear if the trial used the ginkgo extract from the same production batch. Second,
the randomization and double-blinding were done by the authors themselves and thus did not meet the rigor
of the FDA trial standard. This is because the researchers can be biased in evaluation if they
already know who took ginkgo or placebo. Third, the ginkgo extract was in tablets whereas the placebo
in lactose gelatin capsules. It is hard to imagine that they are "of similar appearance". Fourth,
the statistical analysis may be questionable. This reviewer noticed two tests seem to display
changes after ginkgo uptake clearly bigger than after placebo change.
So, after having discussed the available clinical evidence on the efficacy of ginkgo in memory enhancement
in healthy adults, what can we draw for conclusion?
One thing for sure is that ginkgo is not magic bullet to make anybody smart. However, although a role
of ginkgo in memory enhancement of healthy adults appears elusive, if we take into account of the modest efficacy of ginkgo in improving memory impairment
and dementia, it is safe to say
that, when taken by healthy old adults, ginkgo may have a positive effect on maintaining
mental performance and delaying the occurrence of memory impairment associated with aging.
Go to previous part
Reference
1. 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.
2. 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.
3. Cockle SM, Kimber S, Hindmarch I. The effects of Ginkgo biloba extract (LI 1370) supplementation on activities of
daily living in free living older volunteers: a questionnaire survey. Hum Psychopharmacol. 2000 Jun;15(4):227-235.
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