Changes in antioxidant status, blood pressure, and lymphocyte DNA damage from grape juice supplementation

In a placebo-controlled double-blinded study, the effect of 8 weeks of grape juice was compared to the effect of isocaloric placebo juice. Volunteers with a systolic blood pressure > 130 mmHg and diastolic blood pressure > 90 mmHg were recruited. A total of 40 healthy subjects were randomized to receive isocaloric juices for 8 weeks. Twenty-one subjects were instructed to consume 5.5 mL/kg daily of grape juice (GJ), and 19 subjects consumed placebo juice (PJ). Plasma antioxidant vitamin C, total radical trapping antioxidant capacity, blood pressure, and lymphocyte DNA damage were assessed pre- and postsupplementation. Plasma total radical-trapping antioxidant potential showed an increase at the level of 1.31 +/- 0.01 (postsupplementation) versus 1.33 +/- 0.01 (presupplementation) (P < 0.1). Grape juice consumption resulted in a 26% decrease in lymphocyte DNA (both hydrogen peroxide treated or spontaneous) in the grape juice group, while no difference was found in the PJ group. Consuming moderate amounts of daily grape juice may favorably affect antioxidant defense systems and lymphocyte DNA damage in hypertensive individuals.