Increases in human plasma antioxidant capacity after consumption of controlled diets high in fruit and vegetables

Background: The putative beneficial effects of an increased consumption of fruit and vegetables have been associated with antioxidant nutrients. However, the effect of fruit and vegetable consumption on the overall antioxidant status in humans is unclear. Objective: The objective of this study was to investigate whether a diet rich in fruit and vegetables would affect the antioxidant capacity of human plasma. Design: Thirty-six healthy nonsmokers resided in a metabolic research unit and consumed 2 sets of controlled diets. Diet A contained 10 servings of fruit and vegetables each day for 15 d. Diet B was the same as diet A, except diet B also provided 2 servings of broccoli each day on days 6-10. There was a free-living period of a minimum of 6 wk between the 2 experiments using either diet A or diet B. Fasting plasma antioxidant capacity, measured as oxygen radical absorbance capacity (ORAC), and alpha-tocopherol concentrations were determined on days 1, 6, 11, and 16. Results: The fasting baseline plasma ORAC of these subjects was significantly correlated with their estimated daily intake of total antioxidants from fruit and vegetables during the previous year. Plasma ORAC of these subjects was significantly increased by both diets A and B. This increase in ORAC could not be explained by the increase in the plasma alpha-tocopherol concentration. Conclusion: Increased consumption of fruit and vegetables can increase the plasma antioxidant capacity in humans.