A steady decrease in the incidence of colorectal cancer since the mid 1980s is probably attributable more to early screening and polypectomy than to changes in diet and lifestyle.
Researchers at the University of Illinois at Chicago College of Medicine arrived at the finding after analyzing data from several population-based studies, including the National Cancer Institute's Surveillance, Epidemiology, and End Results program. They compared exposure to such risk factors as dietary fat and fiber, energy intake, physical activity, serum cholesterol, cigarette smoking, and obesity with the incidence of colorectal cancer in the United States from 1973 to 1994. Their analysis also included data on Medicare-reimbursed colonoscopic polypectomies.
Voelker R. Colorectal Cancer Decline. JAMA. 1999;282(12):1121. doi:10.1001/jama.282.12.1121-JQU90007-4-1