People who have more than five alcoholic drinks a day increase their risk of having a stroke by more than 60%, research suggests.

But two a day could reduce the risk of the ischemic stroke, the most common kind by 30%.

Over 100,000 people have a first stroke each year in England and Wales, and stroke causes almost 60,000 deaths annually.

Ischemic strokes, which occur when a blood clot interrupts the blood supply to part of the brain, account for 80% of all strokes.

Advised daily alcohol limits

Men - 3 to 4 units Women - 2 to 3 units

The rest are hemorrhagic strokes, caused when a blood vessel in the brain bursts.

Researchers from the Tulane University School of Public Health and Tropical Medicine in New Orleans, analysed 35 previously published studies into the link between stroke and alcohol carried out between 1966 and 2002.

The team compared the stroke risk for people who drank alcohol with those who did not.

'Important and timely'

Combining data from all the studies, they estimated drinking more than five drinks a day (60 grammes) increased the overall risk of having a stroke by 64%.

The risk of having an ischemic stroke increased by 69%, and the risk of an hemorrhagic stroke doubled.

However, drinking less than 12 grammes a day reduced the overall risk of stroke by 17%, ischemic stroke by 20%.

Drinking one to two drinks a day (12 to 24 grammes) reduced the risk of having an ischemic stroke by 28%.

We wouldn't encourage people to take up drinking to prevent them having a stroke Stroke Association spokeswoman

The authors, led by Kristi Reynolds, writing in the Journal of the American Medical Association, said: "Given the widespread consumption of alcohol in the general population and the recognised health and economic burdens of stroke, our findings are both important and timely.

"Our study strongly suggests that reducing alcohol consumption in heavy drinkers should be an important approach to prevention of stroke in the general population.

"Our study also suggests that moderate alcohol consumption reduces risk of ischemic stroke."

'Moderation'

But the researchers added: "The implications of these findings should be examined cautiously.

"Any advice regarding the consumption of alcohol should be tailored to the individual patient's risks and potential benefits."

The UK's Stroke Association advises people should only drink "in moderation".

A spokeswoman told BBC News Online: "Anything that curbs people's alcohol intake can only be a good thing.

"We wouldn't encourage people to take up drinking to prevent them having a stroke but, if they do, they can do it in moderation."

She added: "This research supports other studies that have been carried out that have found benefits from smaller amounts of alcohol."

Although not conclusive, there are some theories about why different amounts of alcohol have different effects on stroke risk.

Alcohol thins the blood, so can prevent clots forming. It may also affect the way cholesterol is carried in the bloodstream, reducing the risk of the build-up of fatty deposits in the blood vessel walls.

But larger amounts, especially if drunk in one go, increases blood pressure, the main risk factor for stroke.

Levels of homocysteine, a substance linked to hardening and furring of the arteries, also rise if large amounts of alcohol are drunk.