Don't put mushrooms in salad. Eat mustard and pepper in moderation. Don't buy bruised celery on sale for half price. And there are affirmative things we can do as well. The same articles discuss some foods that apparently have anti-carcinogenic properties.
Vitamin E helps prevent the process of oxidation that corrupts our body chemistry.
Experts do not yet agree whether doses in excess of the recommended daily allowance afford added protection. The trace mineral selenium is essential to the body's protective de-oxygenation process, though large quantities of this element are toxic. High fiber diets are associated with lower rates of stomach cancer, probably because they shorten the time between ingestion and elimination, so there is less opportunity for foods to putrify in our intestines. In lab experiments, hunger has been shown to slow the aging process in every respect, and evidence is accumulating that the trick works as well in humans. Almost entirely through tests on rats and mice.