Fig. 1.

Dietary phytochemicals blocking or suppressing multi-stage carciniogenesis. Certain chemopreventive phytochemicals in the diet inhibit metabolic activation of the procarcinogens to ultimate electrophilic species and/or their covalent interaction with target cell DNA, thereby blocking the initiation (blocking agents). Alternatively dietary blocking agents can stimulate the detoxification of the pro- or ultimate carcinogens. Others suppress the later steps (promotion and progression) of multi-stage carcinogenesis (suppressing agents). Some phytochemicals can act as both blocking and suppressing agents. Adapted from reference 1.