Previous studies have generally established that a glass or two of red wine every day helps combat heart and circulatory disease by dilating blood vessels.
But the picture has been confused, because not all red wines have the same kinds of polyphenols or in the same concentrations.
In tests using endothelial cells – the cells which line the arteries and where polyphenols are believed to have their positive affect – British scientists identified the most active members of the polyphenol family, which are called procyanidins.
They then tested red wines from the Gers department, in the French Pyrenees, and from Nuoro province on the Italian island of Sardinia, where local men are famous for their longevity.
Wines from these two regions had remarkably high levels of procyanidins – often five to 10 times more than wines that were tested from Australia, South Africa and the United States.
The secret to the Sardinian and Gers wines lies partly in the grape seeds and in time-honoured wine growing methods, the paper says. In Gers, a local variety of grape called Tannat, which is rarely grown elsewhere, also yields rich amounts of procyanidins.
"The traditional production methods used in Sardinia and southwestern France ensure that the beneficial compounds, procyanidins are efficiently extracted," said Robert Corder from Queen Mary's William Harvey Research Institute in London, co-author of the paper.
"This may explain the strong association between consumption of traditional tannic wines with overall wellbeing, reflected in greater longevity."