29th Annual Meeting • American Society of Preventive Oncology San Francisco, CA • March 13–15, 2005

Isothiocyanates and indoles from Brassica vegetables (e.g., broccoli) modify phase I and II enzyme systems responsible for the metabolism of endogenous and exogenous carcinogens. These vegetables also contain micronutrients that may provide additional DNA protection. This randomized crossover trial compares the effects of a Brassica vegetable intervention (BV) against a micronutrient and fiber supplementation intervention (M F) on urinary F2-isoprostane levels (F2-iP), a stable biomarker of systemic oxidative stress. Subjects (n 20) were monitored by repeated 24-hour recalls and questionnaire. Urinary F2-iP levels were measured by mass spectrometry from first-morning urine samples collected at baseline and after each intervention, and change in natural log-transformed urinary F2-iP levels was analyzed using repeated-measures regression. Brassica consumption increased from 2 g/day during the baseline or M F intervention periods to 218 g/day during the Brassica intervention, while intakes of most antioxidant vitamins and minerals were significantly greater during the M F intervention. F2-iP levels significantly decreased 22% with participation in the Brassica intervention compared to baseline or the M F intervention (P 0.05). However, urinary F2-iP levels did not significantly differ between baseline and the M F intervention (difference, 0.2%; P 0.98). These results suggest that Brassica consumption reduces oxidative stress independent of vitamin and mineral content.