Grape juice, but not orange juice or grapefruit juice, inhibits human platelet aggregation

Coronary artery disease is responsible for much mortality and morbidity aro und the world. Platelets are involved in atherosclerotic disease developmen t and the reduction of platelet activity by medications reduces the inciden ce and severity of disease. Red wine and grapes contain polyphenolic compou nds, including flavonoids, which can reduce platelet aggregation and have b een associated with lower rates of cardiovascular disease. Citrus fruits co ntain different classes of polyphenolics that may not share the same proper ties. This study evaluated whether commercial grape, orange and grapefruit juices, taken daily, reduce ex vivo platelet activity, In a randomized cros s-over design, ten healthy human subjects (ages 26-58 y, five of each gende r) drank 5-7.5 mL/(kg . d) of purple grape juice, orange juice or grapefrui t juice for 7-10 d each. Platelet aggregation (whole blood impedance aggreg ometry, Chronolog Model #590) at baseline was compared to results after con sumption of each juice, Drinking purple grape juice for one week reduced th e whole blood platelet aggregation response to 1 mg/L of collagen by 77% (f rom 17.9 +/- 2.3 to 4.0 +/- 6.8 ohms, P = 0,0002), Orange juice and grapefr uit juice had no effect on platelet aggregation. The purple grape juice had approximately three times the total polyphenolic concentration of the citr us juices and was a potent platelet inhibitor in healthy subjects while the citrus juices showed no effect. The platelet inhibitory effect of the flav onoids in grape juice may decrease the risk of coronary thrombosis and myoc ardial infarction.