http://www.lef.org/magazine/mag2007/sep2007_report_grapeseed_02.htm said:
Protecting Cardiovascular Health with Whole Grape Extract
By Julius G. Goepp, MD
Keeping Platelets Slippery
The formation of abnormal arterial blood clots (thrombosis) is a primary cause of heart attack and stroke. Thrombosis is the pathological clumping together of platelets, the tiny cell fragments in blood normally responsible for healthy blood coagulation after injury. There are many chemical triggers that cause platelets to clump, or aggregate, and laboratory studies have demonstrated how the polyphenols found in red grape products (including grape seed extracts) act powerfully to regulate platelet aggregation.37-40
In humans, strong support for the health-promoting effect of polyphenols from red grapes comes both from studies of large populations and from clinical trials.41 People who live in cultures where moderate red wine is consumed regularly have lower rates of illness and death from coronary heart disease, and that effect has been tracked in part to decreased platelet activity.42,43
Researchers in Chile determined the coagulation-related risk reduction more specifically when they studied two groups of 21 healthy young men given a Mediterranean diet or a high-fat diet for 90 days.44,45 For one month in the middle of that period, the men drank 8 ounces of red wine daily, and various blood factors associated with clotting were determined throughout the study. Regardless of whether the men ate the healthful Mediterranean diet or the riskier high-fat diet, when red wine was added to the mix, clotting factors decreased substantially.
Intriguing research supports the role of red grapes in averting aberrant platelet aggregation and coagulation. In 2002, Italian scientists showed that when they gave 20 healthy subjects 10 ounces per day of either red or white wine (both with the same alcohol concentration), the red wine-drinking subjects had significantly lower platelet aggregation after a stimulus than did the white wine-drinkers.46
Not to be outdone, researchers in Frances Bordeaux region showed that it didnt even have to be red wine, so long as the source of the beverage was the whole grape.47 In a study that can only be described as sophisticated, these scientists randomly assigned healthy volunteers to drink either one ounce of vodka (no polyphenols) or Armagnac, a distilled brandy derived from polyphenol-rich grapes.48 The researchers found that after 14 days, platelet aggregation in the Armagnac group was reduced by 31%, compared to only 11% in the vodka group.47 Equally importantly, two weeks after the alcohol consumption stopped, the vodka drinkers experienced a rebound increase of platelet aggregation, which was not seen in the Armagnac group. These results point to the importance of grape polyphenols as the source of the benefits.
A study from China further illustrated the blessings of the grape.49 Scientists investigated the effects of both red wine and resveratrol, one of the main components of grape extracts, on aggregation of platelets from healthy human volunteers. When they treated the platelets with resveratrol they found that aggregation was inhibited in direct proportion to the amount of resveratrol used. When they conducted the same experiment using rabbits with elevated serum cholesterol and increased platelet aggregation, the researchers were again able to demonstrate potent reduction using grape extract-derived resveratrol. These results provide strong evidence that red grape polyphenols such as resveratrol produce their cardioprotective effects at least in part by inhibiting platelet aggregation.
Some skeptics have suggested that the effects of extracts are only seen in the laboratory, where they can be directly applied to the cells being studied.50 It has been convincingly demonstrated, however, that the grape extract components are in fact absorbed from the human intestinal tract in large enough quantities to cause reduction in risk of atherosclerosis.51 This effect can be enhanced when the extracts are high in the polyphenols extracted from grape seeds, and contain a large proportion of the short-chain polyphenols known as oligomers.52-54