Good news for chocoholics everywhere. A few squares of dark chocolate every day could help stave off heart disease, researchers have found.

The anti-oxidants may prevent arteries narrowing and hardening, according to researchers at Zurich's University Hospital, Switzerland.

The scientists reached their conclusion after testing a group of 20 healthy male smokers.

The men were asked not to eat foods rich in anti-oxidants, such as onions, apples and cabbage, before being fed 40-gram portions of different types of chocolate.

Smokers have an increased risk of hardened arteries and heart disease.

But after two hours, ultrasound scans revealed that dark chocolate consisting of at least 74 percent cocoa solids had "significantly improved" blood flow.

Further tests revealed that platelet activity linked to the formation of blood clots had been halved.

White chocolate produced none of the beneficial effects.

Writing in the journal Heart this week the authors said dark chocolate had more anti-oxidants per gram than many other foods whose virtues were already recognized, such as red wine, green tea and berries.

They concluded: "A small daily treat of dark chocolate may substantially increase the amount of anti-oxidant intake and beneficially affect vascular health."

Research published by the American Heart Association earlier this year said a daily bar-sized helping of dark chocolate could lower blood pressure and improve insulin resistance.

Editor: Donald