ABSTRACT
Improving Public Health ...........................................................................81 3.13 Public Perception of Risk and Resulting Behavior ..................................83 3.14 Conclusions................................................................................................85 References ...........................................................................................................86
Nitrite preservatives in processed meats lead to the formation of carcinogenic nitrosamines (NAs), while smoking and cooking of meats leads to the formation of polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines (HCAs). Cigarette smoke is also a potent source of NA, PAH, and HCA carcinogens. Conversely, consumption of vegetables, spices, and green tea are associated with
decreased cancer risk, and many phytochemicals from these sources are proven chemoprotective agents in animal models. NAs, PAHs, and HCAs are stable secondary carcinogens, which are “bioactivated” by P450-based Phase I metabolism to form reactive, ultimate carcinogens. This is also required for effective metabolism, as it allows them to be conjugated (Phase II metabolism) and excreted, preventing the accumulation of parent compounds in areas like the adipose and brain tissue. Thus, the goal in cancer prevention is to find the optimal balance between Phase I and II activities, which allow clearance, while minimizing the accumulation of reactive intermediates. Smoking and regular consumption of cooked meats are negative influences, as P450 enzymes are induced and bioactivation becomes too rapid for Phase II reactions to keep pace. Chemoprotective phytochemicals improve the metabolic balance by antagonizing P450 induction, by competitively inhibiting P450 enzymes, and by inducing the expression of Phase II enzymes. Thus, phytochemical intake can dramatically alter the carcinogenicity of a given exposure to dietary carcinogens.
