Tomato phytochemicals and prostate cancer risk

Mounting evidence over the past decade suggests that the consumption of fresh and processed tomato products is associated with reduced risk of prostate cancer. The emerging hypothesis is that lycopene, the primary red carotenoid in tomatoes, may be the principle phytochemical responsible for this reduction in risk. A number of potential mechanisms by which lycopene may act have emerged, including serving as an important in vivo antioxidant, enhancing cell-to-cell communication via increasing gap junctions between cells, and modulating cell-cycle progression. Although the effect of lycopene is biologically relevant, the tomato is also an excellent source of nutrients, including folate, vitamin C, and various other carotenoids and phytochemicals, such as polyphenols, which also may be associated with lower cancer risk. Tomatoes also contain significant quantities of potassium, as well as some vitamin A and vitamin E. Our laboratory has been interested in identifying specific components or combination of components in tomatoes that are responsible for reducing prostate cancer risk. We carried out cell culture trials to evaluate the effects of tomato carotenoids and tomato polyphenols on growth of prostate cancer cells. We also evaluated the ability of freeze-dried whole-tomato powder or lycopene alone to reduce growth of prostate tumors in rats. This paper reviews the epidemiological evidence, evaluating the relationship between prostate cancer risk and tomato consumption, and presents experimental data from this and other laboratories that support the hypothesis that whole tomato and its phytochemical components reduce the risk of prostate cancer.