reviewed by X. Li, Ph. D.
(credential)
Ginkgo biloba is often marketed as a "smart drug". Although
substantial clinical trials have provided evidence to support that ginkgo may improve memory impairment
in patients of Age-Associated Memory Impairment or
Alzheimer's disease dementia, it does not necessarily
mean that ginkgo may make people smart. Ginkgo may simply restore memory from the abnormal
back to the normal but it may not make the normal further to the smart in healthy people. This
is a clear distinction.
Take fever reducers as an example. A fever reducer may reduce the fever to the normal temperature
but unlikely make people feel cold after further uptake. The real issue is whether there is
direct evidence to support a role of ginkgo in enhancing memory in healthy adults.
A number of trials intended to answer this question. Besides some small trials two large clinical
trials were recently published to study the effect of the standardized ginkgo biloba extract
on enhancing memory in healthy adults1,2. However, this time the answer is less consistent
and more contradictory.
In one trial1, 262 volunteers who had no memory impairment and were of both sexes and of at least
60 years old were enrolled in a so-called placebo-controlled, double-blind, and randomized trial
that was designed to comply with the FDA trial standards. In such trials, patients are randomly
divided into two groups, one group receives the experimental drug and the other receives the dummy.
Neither patients nor researchers know if he or she is taking the drug or dummy. In the trial,
the participants received either 180 mg of the standard ginkgo biloba extract or placebo daily for 6 weeks.
Several standardized neuropsychological measures were taken at the start and the end of the trial for
evaluation of any efficacy of treatment. The participants were also asked to rate any change in memory
themselves.
Statistical analysis showed that volunteers treated with ginkgo exhibited significant improvement in
several test tasks compared with those treated with the placebo. These improved tasks involve delayed free recall
and recognition of non-contextual, auditory-verbal material and delayed recognition of visual
material (i.e. human faces). Moreover, significant more people in the ginkgo group rated their
overall abilities to remember as "improved" than in the placebo group1. Since the participants
themselves did not know whether they took the ginkgo or the placebo, the self-assessment result
reflects how participants feel the efficacy themselves.
Interestingly, a separate trial included 1000 healthy old volunteers taking 120 mg of standardized ginkgo
biloba extract daily for a period of 4 months. Again, significant more people in the ginkgo group felt
they were able to better cope with their daily activities since the end of the first month3.
Therefore, these studies provided positive results suggesting that standardized ginkgo biloba extract
may enhance certain aspects of memory processes in healthy old adults.
Then it comes with another large trial. Continue
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.
More Ginkgo Indications
