The herbal supplement Ginkgo biloba does not prevent mental decline in elderly adults, researchers reported last night.
The herb is a staple of herbal teas and is promoted for its alleged brain-enhancing abilities.
Dr Beth Snitz, of the University of Pittsburgh, USA, and colleagues investigated whether Ginkgo biloba slowed the rate of cognitive decline in adults over the age of 70.
The 3,069 participants, aged 72 to 96 years, took either a twice-daily dose of 120mg extract of Ginkgo biloba or placebo for about six years. Their mental performance was tested with a range of measurements.
At the beginning of the study, the participants had good mental faculties.
Dr Snitz’s team found no evidence of overall benefit in preventing mental decline, or specific aspects such as memory, language, attention, visuospatial abilities and executive functions. The study is published in the Journal of the American Medical Association.
The authors write: "Ginkgo biloba is marketed widely and used with the hope of improving, preventing, or delaying cognitive impairment associated with aging and neurodegenerative disorders such as Alzheimer disease.
"Indeed, in the United States and particularly in Europe, ginkgo biloba is perhaps the most widely used herbal treatment consumed specifically to prevent age-related cognitive decline."
But "we find no evidence that ginkgo biloba slows the rate of cognitive decline in older adults with normal cognition or with mild cognitive impairment."
The researchers explain that these findings are consistent with previous smaller studies on the prevention of decline in cognitive performance, and with the 2009 Cochrane review of ginkgo for dementia and cognitive impairment.
The Cochrane review states: "Overall, evidence that Ginkgo has predictable and clinically significant benefit for people with dementia or cognitive impairment is inconsistent and unreliable."
Snitz, B. E. et al. Ginkgo biloba for Preventing Cognitive Decline in Older Adults: A Randomized Trial. The Journal of the American Medical Association, Vol. 302, December 23/30, 2009, pp. 2663-70.
Birks, J. and Grimley Evans, J. Ginkgo biloba for cognitive impairment and dementia. Cochrane Database of Systematic Reviews 2009, Issue 4.
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