Scientists have discovered compounds in cocoa that can repair blood vessels and boost circulation.

The naturally-occurring antioxidants – known as ­flavanols – are also present in green tea, red wine and some fruit and vegetables.

The average person consumes between 20 and 100mg of flavanols a day – too few to have any medical effect.

Now a team in Germany has created a special cocoa drink containing 321mg of ­flavanols per serving.

The study, published in the Journal of the American College of Cardiology, found that patients with type 2 diabetes who drank three cups a day of the cocoa saw their blood vessel function return to normal within a month.

But Dr Malte Kelm of University Hospital Aachen in Germany, who led the study, warned that ordinary cocoa or chocolate would not have the same effect.

He said: “Dietary flavanols might have an important impact as part of a healthy diet in the prevention of cardiovascular complications in diabetic patients.

“But this study is not about urging those with diabetes to eat more chocolate.”