It will be the first to test gingko as a treatment for those who are still living in the community and are being treated by their GP. Previous trials have concentrated on patients receiving hospital care, where the condition is often more advanced.

We believe gingko may prove more effective if prescribed in a community setting, where patients symptoms are usually less severe, says Dr James Warner, a psychiatrist from Imperial College London and St Marys Hospital, who is leading the study. This trial will help us to find out whether with gingko its a case of the sooner the better, for patients who may benefit from taking it.

Gingko is believed to cause blood vessels to dilate, improving blood flow to the brain, and to thin the blood, making it less likely to clot. Gingko may also have antioxidant effects, protecting nerve cells against biological rusting.

All of these effects would suggest that gingko might slow down a degenerative process such as dementia, says Dr Warner.

It is estimated that 700,000 people in the United Kingdom are affected by the condition, 60 per cent of whom are diagnosed with Alzheimers disease. Patients might occasionally misunderstand who or where they are, forget peoples names or how to get home.

Gingko could provide a cheaper alternative to conventional medicines, with fewer of the potential side effects such as nausea, loss of appetite, tiredness and diarrhoea. A quality gingko extract taken from the Gingko biloba tree costs around