8-Isoprostane F2α excretion is reduced in women by increased vegetable and fruit intake

Background: Health benefits associated with diets rich in vegetables and fruit (VF) are often attributed to the antioxidant activity of their constituent phytochemicals, However, in vivo evidence that VF actually reduce markers of oxidative stress is limited. Objective: An 8-wk dietary intervention was conducted to test the hypothesis that increased VF consumption decreases oxidative stress. Urinary excretion of 8-isoprostane F-2 alpha (8-iso-PGF(2 alpha)) was used as an index of whole-body lipid peroxidation. Design: The diets evaluated had comparable amounts of all macronutrients but varied in their content of VF. After a 2-wk low-VF (3.0 servings/d) run-in diet, 246 women were randomly assigned to receive either 3.6 (low) or 9.2 (high) servings VF/d. The low-VF group was switched to the high-VF diet during the final 2 wk of the study. Blood and first-void urine specimens were obtained at baseline and at 2-wk intervals thereafter. Results: The run-in diet reduced 8-iso-PGF(2 alpha) concentrations by 33% (P < 0.0001). The excretion of 8-iso-PGF(2 alpha) with the low-VF diet remained the same as that with the run-in diet, whereas urinary concentrations of 8-iso-PGF(2 alpha) were further reduced (P < 0.01) by the high-VF diet, either fed throughout the study or when the diet was switched from low to high VF (P = 0.05). The greatest reductions in 8-iso-PGF(2 alpha) were observed in subjects in the highest quartile of baseline concentrations of 8-iso-PGF(2 alpha). Conclusions: A significant reduction in the excretion of 8-isoPGF(2 alpha) was induced by the run-in diet and the high-VF diet. The degree of reduction was related to the subject's baseline urinary concentration of 8-iso-PGF(2 alpha).