The colonic microflora partially or completely ferments carbohydrates that resist digestion and absorption in the small intestine. The fermentation products such as the short chain fatty acids play a key physiological role. Undigested carbohydrate that reaches the large intestine softens stool consistency and increases stool weight and frequency of defecation. With higher dietary fiber intake stool weight tends to be higher and transit time enhances which may contribute to the prevention of large bowel disorders such as constipation, diverticulitis and large bowel cancers [46]. Most non-absorbed carbohydrates have laxative effects, both by increasing bacterial mass or osmotic effects, and by water binding to remaining unfermented fiber. The etiology of cancer involves both inherited and environmental (dietary) factors. Many large studies, mainly observational, have assessed the relationship between fiber intake and the risk of cancer in the colon or rectum. Intervention studies have addressed the effects of dietary fiber on the recurrence of adenoma, which are generally considered as an early marker for colorectal cancer. The overall evidence for an effect of total fiber intake on the risk of colorectal cancer is not considered sufficient to serve as a basis for guidelines on dietary fiber intake. However, individuals with lesser fiber intakes may have an increased risk.