The World Health Organization’s International Agency for Research on Cancer reviewed the evidence linking intake of red and processed meat with colorectal cancer (CRC). Twelve of 18 cohort studies and six of nine case control studies found an association for consumption of processed meat and CRC, while 7 of 14 cohort studies and 7 of 15 case control studies found a positive association for red meat consumption and CRC. A meta-analysis of 10 cohort studies reported a dose-response relationship between meat consumption and CRC risk, with a 17 percent increased risk per 100 g per day of red meat, and an 18 percent increase in risk per 50 g per day of processed meat.

The working group concluded that the evidence was sufficient to classify processed meats as carcinogenic, and red meat as a probable carcinogen. These conclusions were based entirely upon observational studies.

Data from randomized trials (eg, the Women's Health Initiative) have not found a lower incidence of colorectal neoplasia in women whose diets are relatively low in fat (including animal fat). In our view, the absolute risk of CRC associated with intake of red and/or processed meat is small, and modest consumption (one to two times weekly at most) is an acceptable part of a healthy balanced diet.