For the two out of three adults who do not drink alcohol excessively or smoke, the single most important personal choice influencing long-term health is what they eat. Of all the dietary factors thought to be related to cancer, the research evidence is most consistent for an association between increased consumption of fruits and vegetables and a reduced risk from a variety of cancers. Vitamin A may inhibit the initiation and promotion of carcinogenesis in the body. Vitamin A is also a powerful antioxidant and can prevent the formation of free radicals. Although vitamin A-rich fruits and vegetables are considered to be protective against certain cancers, vitamin A supplements are not recommended.
Vitamin C blocks the formation of carcinogenic nitrosamines in the digestive tract.
Vitamin C also acts as an antioxidant by preventing the oxidation of certain chemicals to active carcinogens. Rich food sources of vitamin C are citrus fruits, berries, and most dark-green vegetables like broccoli, spinach, and green peppers. Dietary fiber is the non-digestible or partially digestible materials found in plant cells. Holding onto water in the intestinal tract, increasing stool bulk, which may dilute carcinogen concentration in the colon. Binding with bile acids in the intestinal tract, some of which could convert to co-carcinogens.