Diet and physical activity in the prevention of colorectal cancer.

Diet has been linked to the prevention of colorectal cancer (CRC) and may explain some of the differences in incidence and mortality among various populations. Evidence suggests that a high intake of red and processed meats is associated with an increased risk of CRC. The protective benefits of fiber are unclear, although in some studies fiber is associated with reduced CRC risk. The role of supplements, such as calcium, vitamin D, and folic acid, remains uncertain, and these nutrients cannot be currently recommended for chemoprevention. Obesity and sedentary lifestyle have been associated with an increased risk for colon cancer. Because of the inherent difficulty in studying the effects of specific nutrients, dietary pattern analysis may be a preferable approach to the investigation of the relationship between diet and risk for human diseases. Lifestyle modifications, such as increasing physical activity and consumption of a diet rich in fiber, fruits, vegetables, fish, and poultry and low in red and processed meats, have been advocated for primary prevention of several chronic diseases, and may in fact be beneficial for cancer prevention, particularly CRC.