Chocolate contains flavonoids which can improve blood flow

Professor Roger Corder at London's William Harvey Research Institute has applied for permission to test it on 40 patients with cardiovascular disease.

There is mounting evidence that chemicals called flavonoids found in some forms of chocolate can fight heart disease, blood pressure and strokes.

But experts say the benefits are offset by the high fat and sugar content.

The current research in this area should not be seen as an excuse to over indulge in chocolate at Easter Professor Corder

However, Professor Corder said: "It is probably wrong to say that all dark chocolate is good for you.

"I think it is going to take at least six to 12 months before it is clear which are the best dark chocolate brands to recommend.

"Many of the popular brands of dark chocolate available in the UK will be seen to contain little to make them worth consuming.

"The current research in this area should not be seen as an excuse to over indulge in chocolate at Easter."

He said the fact that chocolate was very high in calories and sugar was a drawback.

'Beneficial effects'

Professor Corder's study will be designed to see whether flavonoids, the key ingredient, can be beneficial to patients with coronary heart disease.

Any possible health benefits will be rigorously recorded.

"I am intrigued about how these ingredients change vascular function. and I think we need to study it more.

"Most of the studies to date have been looking at volunteers or people with milder diseases. We have to look at patients with severe disease," he said.

Flavonoids are not just found in chocolate, but also found in fruit and vegetables and red wine and tea.

Eating five portions of fruit and vegetables a day is a better way to get the heart-protective antioxidants Dr Charmaine Griffiths British Heart Foundation

A study using good quality grape seed extracts could be equally as informative, said Professor Corder.

Studies have suggested the flavonoids they contain can reduce the body's so-called bad cholesterol that causes the hardening of the arteries, strokes and heart attacks.

Professor Corder has already linked the consumption of red wine grown in certain vineyards in Sardinia with longer life.

Dr Charmaine Griffiths, spokeswoman for the British Heart Foundation, said there was some evidence small quantities of dark chocolate might have short-term beneficial effects on circulation.

'Better ways'

"But it is important to remember that chocolate is far more often part of the problem for heart health than the solution.

"We are certainly not suggesting people never eat chocolate - everyone can enjoy a treat from time to time - but there are much better ways of looking after your heart.

"Eating five portions of fruit and vegetables a day is a better way to get the heart-protective antioxidants without having to worry so much about the fats and sugars packed into chocolate."