ATLANTA, GEORGIA. Studies on diet and cancer have proliferated since Doll and Peto’s landmark 1981 report, estimating that 35 per cent of deaths from cancer could be attributed to dietary factors. The possibility that red and processed meat could increase risk of colorectal cancer has been investigated in many studies, with varying results. A link is frequently found, but the strength of the link and relevant types of meat are often unclear.
Now researchers from the American Cancer Society have examined the risks of long-term meat intake with colorectal cancer, and colon and rectal cancer individually. The study involved 148,610 adults who were part of the Cancer Prevention Study II (CPS II). Meat intake was assessed by questionnaire in 1982 and again in 1992/1993. By follow-up in 2001, 1667 cases of colorectal cancer had been diagnosed. Red meat and processed meat intake in 1992/1993 was linked to a higher risk of colon cancer, once age and energy intake were taken into account. However, the effect was no longer significant when BMI, smoking, and other non- dietary factors were considered. Those who ate the most processed meat in 1992/1993, as well as in 1982, were at 50 per cent increased risk of distal colon cancer. Those with the highest ratio of red meat to poultry and fish had an increased distal colon cancer risk of 53 per cent. High consumption of red meat reported in both 1982 and 1992/1993 was associated with a 43 per cent higher risk of rectal cancer. Prolonged high intake of poultry and fish was weakly linked to reduced risk of both proximal and distal colon cancer independently of red meat intake.
The study also confirms the continuing importance of factors such as BMI, smoking and physical activity in
the development of colon and rectal cancers. Commenting on the study in an editorial, Walter C. Willett,
M.D., explains that the relation between meat consumption and colon cancer is strong, but the overall data
are not yet conclusive.