Behind the headlines: Ginkgo biloba for Alzheimer’s
We’ve all seen stories and adverts for products that claim to improve your memory or boost the brain. Widely available, at a cost, these products tempt many who are looking for something that could help relieve the symptoms of Alzheimer’s. One, ginkgo biloba, has been extensively researched and sadly there’s now convincing evidence it can neither prevent nor treat Alzheimer’s. Here we look at some of that data.
The evidence – clinical trials
Ginkgo biloba, which can be called ginkgo or gingko, is also known as the maidenhair tree. Gingko seeds have been used in China for centuries to treat a range of health conditions. Extracts from the leaf are used in both China and Europe today to make tablets or teas.
Anecdotally, people have reported improved memory and thinking skills when taking ginkgo. To test these claims, researchers have used ginkgo in clinical trials. The first trials took place in the 70s and two large trials completed just last year. Clinical trials to test any potential treatment are essential – to assess safety as well as effectiveness.
Clinical trials have allowed ginkgo to be tested in large groups of patients against a placebo, or dummy, treatment. Clinical trials tell us if something really is having an effect, or reported benefits are just due to chance, or a placebo effect.
This Cochrane Summary from 2009 looked at every clinical trial into the effects of ginkgo on Alzheimer’s disease. These summaries systematically look at all the available data and include all clinical trials, which meet quality criteria, for analysis. The results of the trials are scrutinised and summarised. In this case, the summary includes 36 clinical trials of ginkgo for Alzheimer’s, which included thousands of people. While one study showed benefit, the remainder did not. The authors conclude ‘The evidence that Ginkgo biloba has predictable and clinically significant benefit for people with dementia or cognitive impairment is inconsistent and unreliable’.
Digging even deeper
Despite this negative conclusion further research has been undertaken. A clinical trial published last year in The Lancet looked to uncover whether ginkgo could be used to prevent Alzheimer’s disease. 2,854 people took part and were followed up for five years. They found that long term use of ginkgo did not reduce the risk of developing Alzheimer’s disease.
A similar long term study in the US found ginkgo was ineffective in reducing the development of dementia and Alzheimer’s. This is the largest ever trial into the effects of ginkgo on Alzheimer’s disease, following over 3,000 people for six years. Participants were randomly assigned to receive twice daily doses of either a placebo or 120 milligrams of ginkgo biloba extract. They were followed up every six months for six years. There was no difference in rates of dementia or Alzheimer’s disease between the ginkgo and placebo groups.
Over 10,000 people have now taken part in properly designed and controlled clinical trials, representing a robust test of ginkgo, but the clear indication coming through is that it can’t be recommended as a treatment or a prevention for Alzheimer’s disease.