Attack of the Killer Tomatoes: Lycopene and Cancer Prevention
Lycopene is an acyclic hydrocarbon carotenoid containing 11 conjugated double bonds in the all-trans form. It lacks provitamin A activity, but has an exceptionally high singlet oxygen quenching ability. Carotenoids are lipid-soluble, transported in the blood by lipoproteins and appear to concentrate in tissues where lipoprotein uptake is high, as in the adrenals, testes, liver, kidney, and prostate. Increased plasma concentrations of lycopene have been shown to elevate lycopene metabolites and reduce lipid, protein, and DNA oxidation. Lycopene predominantly occurs in fresh tomatoes and tomato products such as tomato juice and tomato sauce. Its bioavailability is increased in cooked or processed tomato products and when consumed with oils. Epidemiological studies of lycopene and cancer have correlated increased tomato intake with lower incidence of gastrointestinal, stomach, and prostate cancers while decreasing serum values of lycopene increases the risks for various types of cancer. Lycopene is an effective inhibitor of cell growth and DNA synthesis in human cancer cell cultures and suppresses mammary tumor development in SHN mice and DMBA rat tumor models.