Effect of orange juice intake on vitamin C concentrations and biomarkers of antioxidant status in humans

Abstract

Background: Consumption of fruit and vegetables is associated with improved health and a decreased prevalence of chronic degenerative processes. Objectives: The objectives were to assess the bioavailability of vitamin C from orange juice and its influence on plasma vitamin C and 8-epi-prostaglandin F2α (8-epi-PGF2α) concentrations in a healthy human population. Design: Six men and 6 women consumed 500 mL commercial fresh-squeezed orange juice/d for 14 d, corresponding to an intake of 250 mg ascorbic acid/d. On the first day of the study, the subjects drank the juice in one dose (dose-response study), and on days 2-14 they consumed 250 mL in the morning and 250 mL in the afternoon. Blood was collected every hour for 6 h on the first day and again on days 7 and 14. Results: Baseline plasma vitamin C concentrations were significantly higher (P = 0.03) among the women than among the men (56.4 ± 4.4 compared with 44.3 ± 3.5 μmol/L). In the dose-response study, the maximum increase in plasma vitamin C occurred 3 h postdose in both the men and the women. Vitamin C concentrations remained significantly higher on days 7 and 14 than at baseline. Baseline concentrations of 8-epi-PGF2α were significantly higher (P = 0.03) among the men than among the women (249.6 ± 25.4 compared with 177.7 ± 6.2 pg/mL) but decreased significantly (P = 0.04) by day 14 of the intervention. A significant inverse correlation was observed between vitamin C and 8-epi-PGF2α (r = -0.791, P = 0.0022). Among smokers, baseline vitamin C was lower and 8-epi-PGF2α higher than among nonsmokers. Conclusions: Drinking orange juice (500 mL/d) increases plasma concentrations of vitamin C and reduces concentrations of 8-epi-PGF 2α in humans. These effects were significantly more pronounced in smokers.