[Recent advances for research on chemopreventive effect of beta-carotene]

Cancer is the culmination of the chronic disease process, and can be attributed the interactions of environment and genes. An optimistic message for 35% cancer prevention may be in dietary constituents, food supply. Carotenoids are isoprenoid compounds synthesized in plants and microorganisms, but not in animals. Human tissue contains only a fraction of the total number of carotenoids(nearly 600 have been identified in nature) present in food supply such as fruit and vegetables. People with high intake of beta-Carotene have a reduced risk of cancer. This outcome seems to bear relation to the chemical to quench singlet oxygen and inhibit peroxyl free radical reaction. But the ATBC and CARET cancer prevention study found the increase in lung cancer incidence in smokers and asbestos. This adverse effect may be explained by beta-Carotene prooxidant when tobacco smoke exposure and oxidative stress occurs, and cellular DNA damage was further aggrevated. Phase I enzymes were induced. Cell transformation was enhanced.