Plant anticarcinogens.

There is strong epidemiological evidence to suggest that the consumption of diets rich in plant materials is associated with a reduced risk of cancer. Human beings are probably adapted to consume relatively large quantities of biologically active phytochemicals derived from as many as 300 different plant genera. Plant foods contain a variety of potentially anticarcinogenic secondary metabolites, and these can conveniently be classified as blocking agents and suppressing agents. Blocking agents modulate the activation and detoxification of carcinogens, whereas suppressing agents are thought to modify post-initiation events including cellular differentiation, proliferation and apoptosis. The full significance of these mechanisms needs to be assessed in further research, preferably using suitable biomarkers in human subjects.