Natural agents in the prevention of cancer, part two: preclinical data and chemoprevention for common cancers.

This paper is the second of a series examining the use of nutritional supplements as chemopreventive agents. The animal and in vitro data are reviewed in support of their use. Human safety data and mechanisms of action are described as well. Many over-the-counter dietary supplements have been shown to have significant chemopreventive activity in preclinical studies. Few side effects are associated with even long-term use of these agents. Along with dietary and lifestyle risk-reducing strategies, nutritional supplementation appears to be a viable intervention for those considered to be at high risk of developing cancer.