Nutrients and digestive tract cancers
Diet changes also are important in digestive tract cancers--those arising in the mouth, esophagus, stomach, colon, rectum, or liver. Researchers have focused on changing the course of the disease in people who have precancerous conditions, and have identified a protective role for certain nutrients. The benefits of beta-carotene were studied in a group of men and women in Arizona who had precancerous changes in their mouths (which doctors refer to with the technical name leukoplakia, which simply means "white spots"). These people were at risk for oral cancer. The research team asked each of them to take 60-milligram beta-carotene supplements, the equivalent of four carrots, per day.
For many, the spots in their mouths regressed or disappeared. After six months the protective effect was so strong that even those who then discontinued the beta-carotene supplements still showed lingering protection a year later. As we saw earlier, however, you are better off getting your beta-carotene, along with hundreds of its relatives, from vegetables and fruits rather than pills.
Healthy Eating for Life to Prevent and Treat Cancer, Physicians Committee For Responsible Medicine.