Jean Paul Broustet, of Hart-Leveque Hospital in the Bordeaux region of France, says in the journal Heart that the Cabernet Sauvignon grape has particularly large amounts of the anti-oxidant resveratrol, which alters the balance between "good" and "bad" cholesterol in the blood, helping to prevent heart attacks.
Even when diluted 100 times, red wine is still a more powerful anti- oxidant than is vitamin E. This might account for the "French paradox" - that although Mediterranean populations have high-fat diets, they suffer low rates of heart disease.
The longer the grapes stay on the stem, the higher the concentration of tannins - bitter agents in the wine. Tannins, combined with alcohol, reduce the "stickiness" of the blood cells known as platelets, thus lowering the risk of clots forming in the blood vessels.
One study, which involved feeding dogs Chateauneuf du Pape and grape juice, showed that the wine was far more effective at reducing constrictions in blood-flow caused by a sudden aggregation of platelets.
Dr Broustet suggests, however, that the beneficial effects of a good red wine have more to do with taste and bouquet - and the good company enjoyed while drinking. He blames problems such as cirrhosis of the liver on over-indulgence.