Tomato and soy phytochemicals: In vivo biodistribution, bioavailability, antioxidant/oxidative environment regulation, and prostate biomarker modulation

Tomato-based products and soy foods contain compounds that have been shown to beneficially impact health, however, adequate information on phytochemical in vivo biodistribution and bioavailability, as well as the effect of consumption of these foods on antioxidant/oxidative environment regulation and prostate biomarker modulation is not available. First, in a study of healthy individuals, the change in plasma lycopene and resistance of lipoproteins to ex vivo oxidative stress following variation in tomato-based product intake was assessed. Total plasma lycopene concentrations significantly decreased during a 7-day washout period and significantly increased after consumption of tomato-based foods for 15 days. A complex array of plasma lycopene isomers was also detected throughout the study. Additionally, dietary intervention with tomato-based products significantly enhanced the protection of lipoproteins to ex vivo oxidative stress. Secondly, a study was performed to determine if men with prostate cancer would consume tomato-based products or a soy protein supplement daily during the period between their diagnosis and surgery (i.e. a period of 2--4 weeks). In addition, this study was conducted to examine in vivo concentrations of phytochemicals from these foods and their effect on modulating hormone levels. All study participants were extremely compliant. Tomato-based product or soy protein supplement intake significantly increased plasma and prostate tissue carotenoid concentrations or urinary and prostate tissue isoflavone levels, respectively. Lycopene isomer patterns in plasma and prostate were unique, yet complicated. It also appears that tomato sauce and tomato soup provide a more bioavailable form of lycopene than vegetable juice. In addition, this study showed that dietary intervention with tomato-based products and soy decreases serum PSA concentrations. A significant increase in lycopene and isoflavone concentrations following tomato and/or soy intake suggests a preferential uptake and requirement of these phytochemical-containing foods in biological processes related to reducing both oxidative stress and prostate cancer progression. Finally, using new technologies, an evaluation of stored samples from the first two studies was conducted to assess the influence 2--4 weeks of tomato-based product consumption had on additional markers of oxidative stress in healthy participants and prostate cancer patients. Tomato-based product intake significantly increased plasma lipid-soluble antioxidant capacity in each of the study populations, while decreasing urinary levels of 8-iso-PGF 2alpha in prostate cancer patients.