Association between High Intake of Lycopene-rich Foods (Tomato, Grapefruit, Watermelon, Papaya) and Reduced Risk of Cancer

The consumption of lycopene and lycopene-rich foods, such as tomato, papaya, watermelon and grapefruit, has been associated with decreased risk of several cancers, including prostatic, lung and gastrointestinal cancers. In vitro studies demonstrated that lycopene may inhibit the growth of several types of cancer cells and provided valuable insights into the mechanisms by which lycopene exert their cellular and intracellular effects. Mechanisms implicated in the prevention of cancer incidence and progression by lycopene-rich foods include: modulation of redox activity, enzyme detoxyfication, inhibition of cell proliferation and apoptosis induction, regulation of growth factor and hormone signalling, inhibition of cell adhesion and angiogenesis, inhibition of cholesterol synthesis, immunomodulation and enhancement of gap junction communication. A good number of animal studies indicates a protective effect of pure lycopene or lycopene-rich foods on prostatic, gastro-intestinal and lung tumorigenesis. Although numerous epidemiological studies demonstrate that lycopene and lycopene-rich foods may reduce cancer risk, intervention trials establishing a direct link between lycopene and/or lycopene-rich foods and cancer prevention are still few and controversial. This review examines the experimental and clinical evidences for a preventive role of lycopene and lycopene-rich foods on cancer as well as the mechanisms of action implicated. In addition, it speculates on the interactions existing between lycopene and other bioactive food components in cancer prevention.