Ginkgo's Benefits Don't Last Long

Summarized by Robert W. Griffith, MD
August 3, 2005

Introduction

Extracts of Ginkgo biloba have been used for thousands of years in Far Eastern countries to treat different conditions. More recently, ginkgo has found favor with Westerners as a potential treatment of 'cognitive disorders', as encountered in Alzheimer's disease and vascular dementia. And it's been shown that single or just a few doses of ginkgo given to young healthy volunteers can improve performance on memory and attention tests. Disappointing clinical studies have led to the suggestion that ginkgo may lose it's effectiveness in older people. However, the possible longer-term effects of ginkgo have not been assessed in rigidly-conducted psychological studies. Here is a summary of such a study, which was published recently in the journal Psychopharmacology.

What was done

Post-menopausal women who were healthy were recruited to this study, which was done at King's College Hospital, London UK. They were randomly assigned to receive Ginkgo biloba tablets or a matching dummy tablet (placebo) for 6 weeks.¹

The volunteers were classified as Stage 1 (early stage) of the menopause if it was less than 5 years from their last menstrual period, and Stage 2 (late stage) if it was more than 5 years.

Tests of mental flexibility, planning, memory, and sustained attention were done at baseline and after 6 weeks. Ratings of mood, sleepiness, and bodily or menopausal symptoms were done at the same intervals.

What was found

Ninety-six women aged 51-67 were enrolled, but 9 dropped out for various reasons during the 6 weeks. This left 43 women in Stage 1, and 44 in Stage 2.

The only improvement related to ginkgo administration was in the area of brain functioning (cognitive ability). Performance in mental flexibility tests was found to be improved by 6 weeks of ginkgo, but only in the Stage 2 subjects; these subjects were older (as expected) and had significantly poorer results at baseline than the Stage 1 volunteers.

All subjects reported improved menopausal and anxiety symptoms at the end of the 6-week period, regardless of whether they took ginkgo or placebo. There were no effects on mood, or the other symptoms measured.

What these findings mean

This study, together with results from other trials, suggest that the published benefits of ginkgo - improved memory, attention, and mental flexibility - do not persist beyond the first few days of treatment. The authors of this study have reported a similar trial in healthy young volunteers, and found a similar lack of effect on memory and attention after 6 weeks; they also found no effect on mental flexibility in young subjects.²

Clearly the measurable effects of ginkgo are small and fleeting, at best. It seems likely that tolerance to the substance develops; in other words, the body fails to react to repeated doses because the tissues become 'used to' the presence of the molecules and fail to react to it, or the substance is broken down and removed more rapidly by the body over time, which is a known occurrence with certain drugs. Either way, taking ginkgo in the recommended doses has little to recommend it.

Because ginkgo decreases blood platelet aggregation (stickiness), there is some concern that it may increase risk of intracranial (brain) hemorrhage; in fact, there have been several reports of bleeding complications associated with ginkgo use. It would be unadvisable, therefore, for people to self-medicate with ginkgo at high doses in the hope of obtaining effectiveness.

Source

• Limited cognitive benefits in stage 2+ postmenopausal women after 6 weeks of treatment with Ginkgo biloba. S. Elsabagh, DE. Hartley, SE. File, Psychopharm, 2005, vol. 19, pp. 173--181

Footnotes
1. Ginkgo One-A-Day 120 mg tablets contain standard extract from the green leaves of the Ginkgo biloba tree, comprising 25% ginkgo flavenoids and 6% terpenoids.
2. Differential cognitive effects of Ginkgo biloba after acute and chronic treatment in healthy volunteers. S. Elsaberg, DE. Hartley, O. Ali,  et al., Psychopharmacology, 2005, vol. 179, pp. 437--446

Related Links
Alternative Medicine: Ginkgo Biloba
Ginkgo Supplements : Mind the Claims
Moving for Mental Fitness

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