Britain's Alzheimer's Society, together with the Cochrane Collaboration, has published what it claims is the biggest comprehensive review to date on the use of ginkgo biloba for the treatment of dementia. The systematic review has identified 33 previous clinical trials of ginkgo, dating back to 1976.
The society said that this new research provides promising evidence that taking ginkgo biloba can improve memory and overall function for people with dementia.
The review concluded that: "Ginkgo biloba appears to be safe in use with no excessive side effects compared with a placebo. Many of the early trials used unsatisfactory methods, were small, and we cannot exclude publication bias. But overall there is promising evidence of improvement in cognition and function associated with ginkgo. Our view is that there is a need for a large trial using modern methodology to provide robust estimates of the size and mechanism of the treatment effects."
Dr Mike Clarke, speaking on behalf of the Cochrane Collaboration which prepares and promotes reviews of the effects of healthcare interventions, said:"Cochrane Reviews, such as this one, aim to bring together all the relevant evidence, so that it is easier to make well-informed decisions about health care. This review helps to identify the types of research that are now needed to find the best treatments for people with dementia."
Michael McIntyre, a Trustee of the Prince of Wales Foundation for Integrated Health, chair of the European Herbal Practitioners Association and one of the UK's best known medical herbalists, said:" This work is bound to have a major impact, drawing the attention of the medical community to the benefits of this ancient oriental remedy."
The findings have provided the green light for a major new clinical trial of ginkgo in people with early dementia who are looked after by their GP. The new study, to receive funding from the Alzheimer's Society, will recruit 400 people with dementia, following them over a period of six months while they receive treatment either with ginkgo or a placebo.
The trial is being jointly run by Imperial College and the Royal London Homeopathic Hospital.
Dr Richard Harvey, director of research for the Alzheimer's Society, said:"Our new clinical trial will apply modern methods and robust quality controls to finally answer a question that has been hanging in the air for 5000 years."
Ginkgo biloba is an extract from the leaves of the ginkgo tree, which in the UK is more commonly called the maidenhair tree. This tree has survived unchanged in China for more than 200 million years and there is a history of its medicinal use for almost 5000 years.
However a study published earlier this year by scientists in the US called all previous evidence into question when it found that ginkgo biloba has no beneficial effect on memory and related mental functions of healthy older adults.
Dr Peter Fisher, director of research at the Royal London Homeopathic Hospital, said:"Ginkgo contains a number of organic biologically active components. It is the ginkgolides that are unique to the ginkgo tree although it is not fully known which component or components are the ones that give the leaves their medicinal properties."
Dr James Warner, senior lecturer and consultant in Old Age Psychiatry at Imperial College London, added:"The medicinal effects of ginkgo are believed to be gained by causing blood vessels to dilate, improving blood flow to the brain, and through thinning the blood and making it less likely to clot. Ginkgo probably also has some antioxidant effects, protecting nerve cells against biological 'rusting'. All of these effects would suggest that ginkgo might slow down a degenerative process."
Dementia affects one in 20 people over the age of 65 and one in five over the age of 80, according to the Alzheimer's Society. There are currently over 700,000 people in the UK with dementia and more than half of these have Alzheimer's disease.