By David Kiefer, MD
Clinical Assistant Professor, Department of Family Medicine, University of Wisconsin; Clinical Assistant Professor of Medicine, Arizona Center for Integrative Medicine, University of Arizona, Tucson
Dr. Kiefer reports he is a consultant for WebMD.
A review of published research by the World Health Organization concludes that processed meats are probably carcinogenic.
Bouvard V, et al. Carcinogenicity of consumption of red and processed meat. Lancet Oncol 2015 Oct 23. pii: S1470-2045(15)00444-1.
The cancer arm of the World Health Organization, the International Agency for Research on Cancer (IARC), classified red meat as probably carcinogenic (Group 2A category) to humans and processed meat as carcinogenic (Group 1 category) to humans.
A Group 1 classification indicates the scientists felt that there was sufficient evidence that an agent causes cancer; in the case of processed meat, there is causation for colorectal cancer and less so for stomach cancer. The processed meats studied included meats (usually beef and pork, but also other red meats, poultry, offal, and meat byproducts) that were salted, cured, fermented, smoked, or otherwise preserved in some way. Other Group 1 carcinogens are asbestos and tobacco smoking, but the IARC stressed that its report does not quantify carcinogenicity and that it is not saying that eating processed meats is as dangerous as those other carcinogens. A Group 2A carcinogen means there is limited epidemiological evidence for a cancer association but strong mechanistic evidence; in the case of red meat, there is some evidence of a connection with colorectal cancer, pancreatic cancer, and prostate cancer.
This was the result of a review of more than 800 scientific studies (700 studies commented on red meat and 400 commented on processed meat; there was some overlap) spanning 20 years, dozens of types of cancer, many countries, and a diversity of diets. For example, the report mentioned that eating the equivalent of three pieces of bacon (50 g) daily would increase the risk of colorectal cancer by 18%. With respect to red meat, eating the equivalent of ¼ pound (100 g) of hamburger daily could increase the risk of colon cancer by 17%. Other types of red meat that the researchers included, and should be a part of patient counseling, are veal, pork, lamb, mutton, horse (perhaps not a common part of the U.S. diet), and goat. Further interpretation of the report’s results have varied widely among media outlets and health experts; the extra risk from eating red and processed meats probably remains small for individuals, but it adds to other data encouraging people to minimize their red meat intake, and creates a compelling public health argument to address this consumption.
