Ginkgo Biloba for Memory Enhancement in healthy adults
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 adults^1,2. 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.

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