Lowering of oxidative stress improves endothelial function in healthy subjects with habitually low intake of fruit and vegetables: A randomized controlled trial of antioxidant- and polyphenol-rich blackcurrant juice

Inadequate intake of the recommended five-a-day fruit and vegetable portions might contribute to increased cardiovascular disease risk. We assessed the effects of dietary intake of a blackcurrant juice drink, rich in vitamin C and polyphenols, on oxidative stress and vascular function. This was a double-blind, placebo-controlled, parallel group study of 66 healthy adults who habitually consume <2 portions of fruit and vegetables per day. Participants were randomly allocated to consume 250 ml of placebo (flavored water) or low or high blackcurrant juice drink four times a day for 6 weeks. Flow-mediated dilation (FMD) and plasma concentrations of F-2-isoprostanes and vitamin C were measured. In the high blackcurrant juice drink group FMD increased significantly (5.8 +/- 3.1 to 6.9 +/- 3.1%, P=0.022) compared with the placebo group (6.0 +/- 2.2 to 5.1 +/- 2.4%). Plasma vitamin C concentration increased significantly in the low (38.6 +/- 17.6 to 49.4 +/- 21.0 mu mol/L, P < 0.001) and high (34.6 +/- 20.4 to 73.8 +/- 23.3 mu mol/L, P < 0.001) blackcurrant juice drink groups compared with the placebo group (38.1 +/- 21.0 to 29.0 +/- 17.6 mu mol/L). F-2-isoprostane concentrations were significantly lower in the high blackcurrant juice drink group (225 +/- 64 pg/ml) compared with the low blackcurrant juice drink (257 +/- 69 pg/ml, P=0.002) and placebo group (254 +/- 59 pg/ml, P=0.003). At follow-up, changes in plasma vitamin C correlated significantly with changes in FMD (r=0.308, P=0.044). Consumption of blackcurrant juice drink high in vitamin C and polyphenols can decrease oxidative stress and improve vascular health in individuals with habitually low dietary fruit and vegetable intake. (C) 2014 Elsevier Inc. All rights reserved.