Mechanisms for Nutritional Inhibition of Carcinogenesis

The existence of an etiologic relationship between dietary practices and human cancer is supported by data obtained from a variety of sources. Dietary practices may increase or decrease cancer risk depending upon intakes of individual nutrients and their interactions. The multitude and complexities of interrelationships that can exist among dietary constituents possibly accounts for reported inconsistencies among human studies. Nevertheless, based upon laboratory, epidemiological, and clinical data, modification in the dietary habits of humans appears to offer a means of reducing cancer risks. Selective dietary factors have long been recognized as influencing the development of tumors in experimental animals. The intake of various micronutrients has been observed to significantly alter cancer incidence and severity in a variety of experimental circumstances by modifying specific phases of carcinogenesis. Dietary constituents can alter the formation and bioactivation of carcinogens, modify the promotion and progression of neoplastic tissue, modulate immunocompetence, and lead to variations in rates of tumor growth. The influence of individual micronutrients on the constituent steps of carcinogenesis, as discussed in this chapter, continues to be an area of active examination. Continued research will likely supply needed information on the particular role of nutrients and nonnutrients in the carcinogenic process, identify critical times for nutritional intervention, and hopefully lead to sound and accurate dietary recommendations for populations at large.