Cancer-preventive activities of tocopherols and tocotrienols
S. C Picinich,
A. N Kong
C. S. Yang
The cancer-preventive activity of vitamin E has been studied. Whereas some epidemiological studies have suggested a protective effect of vitamin E against cancer formation, many large-scale intervention studies with -tocopherol (usually large doses) have not demonstrated a cancer-preventive effect. Studies on -tocopherol in animal models also have not demonstrated robust cancer prevention effects. One possible explanation for the lack of demonstrable cancer-preventive effects is that high doses of -tocopherol decrease the blood and tissue levels of -tocopherols. It has been suggested that -tocopherol, due to its strong anti-inflammatory and other activities, may be the more effective form of vitamin E in cancer prevention. Our recent results have demonstrated that a -tocopherol-rich mixture of tocopherols inhibits colon, prostate, mammary and lung tumorigenesis in animal models, suggesting that this mixture may have a high potential for applications in the prevention of human cancer. In this review, we discuss biochemical properties of tocopherols, results of possible cancer-preventive effects in humans and animal models and possible mechanisms involved in the inhibition of carcinogenesis. Based on this information, we propose that a -tocopherol-rich mixture of tocopherols is a very promising cancer-preventive agent and warrants extensive future research.