- Polyps free participants with any of the following high risk of colorectal polyps or cancer: (1) family history of colorectal cancer or polyps; (2) current cigarette smoker; (3) obesity (BMI≥30 kg/m2); (4) low intake of fiber (lowest fiber intake quartile: daily intake <16.6g); (5) high intake of red meat and well-done or processed meat (mutageneity index ≥5852).