Effects of blueberry and cranberry juice consumption on the plasma antioxidant capacity of healthy female volunteers

Objective: To assess whether consumption of 500 ml of blueberry juice or cr anberry juice by healthy female subjects increased plasma phenolic content and antioxidant capacity. Design: Latin square arrangement to eliminate ordering effects. After an ov ernight fast, nine volunteers consumed 500 mi of blueberry juice, cranberry juice or a sucrose solution (control); each volunteer participated on thre e occasions one week apart, consuming one of the beverages each time. Blood samples were obtained by venipuncture at intervals up to four hours after consumption of the juices. Urine samples were also obtained four hours afte r consuming the juice. Results: Consumption of cranberry juice resulted in a significant increase in the ability of plasma to reduce potassium nitrosodisulphonate and Fe(III )-2,4,6-Tri(2-pyridyl)-s-triazine, these measures of antioxidant capacity a ttaining a maximum after 60-120 min. This corresponded to a 30% increase in vitamin C and a small but significant increase in total phenols in plasma. Consumption of blueberry juice had no such effects. Conclusion: The increase in plasma antioxidant capacity following consumpti on of cranberry juice could mainly be accounted forby an increase in vitami n C rather than phenolics. This also accounted for the lack of an effect of the phenolic-rich but vitamin C-low blueberry juice.