The view that dietary practices might be a causative factor in cancer is not new. There is increasing evidence that composition of daily food may significantly influence cancer incidence. This may be partially as result of direct toxic effects and partially through the equilibrium of as yet ill-defined cancer-promoting and cancer-inhibiting factors in food.
Some potent carcinogens arise from natural processes, and others are result from the pesticides and herbicides -- many of which have been implicated in cancer -- with which food products have been treated. Mutagens are present in substantial quantities in fruits and vegetables, and carcinogens are formed in cooking as a result of reactions involving proteins or fats. Rancid fats are possible causative agents of colon and breast cancer in humans, and fat intake increases the chances of getting such cancer. In addition, cancer risks are higher among people who are 40% or more overweight and heavy drinking has been linked with cancers of the mouth, larynx and oesophagus. The USA National Academy of Sciences has estimated that pesticides could be responsible for up to 5,800 cases of cancer in every million people.