Some nutritionists suggest that fiber speeds the passage of food through the intestine so cancer-causing agents have less time to affect the colon. But this is only a theory that has not yet been verified. In general, research findings have been inconsistent in linking colon cancer and fiber. However, there is very good data showing that eating plenty of vegetables lowers the risk of colon cancer in other ways.
Vegetables contain vitamins, minerals, and other nutrients that include anti-cancer substances.
Although fiber itself may not fight cancer, it can relieve constipation, reduce colon inflammation and irritable bowel syndrome, lower blood cholesterol and triglyceride levels, and decrease blood sugar levels for diabetics. Diets high in fiber also help people eat less and lose weight because the digestive tract becomes full sooner due to fiber's bulk. In addition, high fiber foods are usually low in fat. Besides vegetables, other good sources of fiber are grains and fruits.