Carotenoids

1. Carotenoids are 40 carbon pigmented compounds, of which approximately 600 have been identified throughout nature. The six main carotenoids found in diet, blood, and tissue are lycopene, β-carotene, α-carotene, β-cryptoxanthin, lutein, and zeaxanthin. 2. The production of retinoids, which promote cell differentiation and inhibit cell proliferation, could be one mechanism for the anticancer activity of carotenoids. However, carotenoids’ multiple conjugated double bonds also make them excellent scavengers of free radicals and thus antioxidants. 3. Epidemiological studies consistently support an inverse relationship between fruit and vegetable consumption and cancer risk. Blood β-carotene concentration has been used as a biomarker of fruit and vegetable intake because β-carotene is plentiful in most fruits and vegetables. 4. Epidemiological studies examine the relationship between tomato/lycopene consumption, serum lycopene levels, and prostate cancer. The prostate is an androgen-responsive tissue, thus the androgens, testosterone, and dihydrotestosterone stimulate proliferation and development of most prostate tumors. Androgens appear to alter lycopene metabolism and, in turn, lycopene may alter androgen metabolism by decreasing the expression of androgen-producing enzymes. 5. To reduce the risk of prostate cancer, it is recommended that men consume at least two servings of tomatoes a week. For β-carotene, it is important to eat the recommended daily servings of fruits and vegetables, especially those high in β-carotene.