Could Ginko cause a stroke?

A herbal supplement taken by thousands of Britons to keep their memory sharp into old age may do more harm than good.

Ginkgo biloba, first used medicinally by the Chinese more than 5,000 years ago, has been thought to stave off Alzheimer's disease and improve circulation.

But research shows it increases the risk of a stroke, while its effects on memory are unclear.

The U.S. study looked at the effect of three tablets a day on 118 men and women aged 85 and over.

Half were given ginkgo biloba tablets or supplements and half were given placebos - dummy pills.

During the three-year trial, seven of those taking the supplement had a stroke or mini-stroke - but none of those in the placebo group did.

Study author Dr Hiroko Dodge, an expert in age-related mental decline, said:

"Ginkgo has been reported to cause bleeding-related complications but the strokes in this case were due to blood clots, not excessive bleeding, and were generally not severe."

During the Oregon State University study 21 people developed memory problems which could be classed as dementia.

Of these, 14 had taken placebos and seven the herbal supplement.

When the researchers took into account how well the volunteers had remembered to take their tablets, however, they found those who followed the instructions the best were 68 per cent less likely to have developed memory problems.

It was unclear whether this was purely chance, said Dr Dodge, whose study is reported in the journal Neurology.

He said: "These results need to be clarified with larger studies but the findings are interesting because ginkgo biloba is widely used, readily available and relatively inexpensive.

"One of the most pressing public health problems is the rapidly growing number of people who, due to age alone, are at high risk of developing dementia.

"The potential to delay or prevent this is of great importance.

"Further studies are needed to determine whether ginkgo biloba has benefits in preventing cognitive decline and whether it is safe."

Around 700,000 Britons have Alzheimer's disease and other forms of dementia.

The number is expected to double in the next 40 years, as the population ages.

Dr Susanne Sorensen, head of research at the Alzheimer's Society, said: "This study adds to a growing body of evidence suggesting ginkgo biloba may not be effective.

"More research is needed on a larger scale."

Michael McIntyre, chairman of the European Herbal Practitioners' Association, also called for further research, but added: "I would have thought the fact they noted that people who reliably took the supplement had a 68 per cent lower risk of developing memory problems was very significant."