Cancer prevention by natural carotenoids.

Epidemiological investigations have shown that cancer risk is inversely related to the consumption of green and yellow vegetables and fruits. Since beta-carotene is present in abundance in these vegetables and fruits, it has been investigated extensively as a possible cancer preventive agent. However, various carotenoids that coexist with beta-carotene in vegetables and fruits also have anticarcinogenic activity. Some of them, such as alpha-carotene, showed higher potency than beta-carotene in suppressing experimental carcinogenesis. Thus, we have carried out more extensive studies on cancer-preventive activities of natural carotenoids, which found that lycopene and lutein had potent anticarcinogenic activity. In the present study, the cancer-preventive activity of phytoene was also confirmed biotechnologically when mammalian cells producing phytoene were resistant to H-ras-induced cell transformation. Further studies on various natural carotenoids besides beta-carotene should be continued to obtain more information about the potential of natural carotenoids in the field of cancer prevention.