Hot dogs, sausages, and corned beef now have something in common with asbestos, benzene, and ionizing radiation. They are in the same class of cancer-causing substances, according to the World Health Organization’s (WHO) cancer agency, the International Agency for Research on Cancer (IARC). The organization’s October 26, 2015 press release states that a group of 22 experts from 10 countries convened by the IARC Monographs Programme classified red meat as “probably carcinogenic to humans” (IARC Group 2A), and processed meat as “carcinogenic to humans” (IARC Group 1). The group made the classifications after “thoroughly reviewing the accumulated scientific literature” and finding an association between consumption of red meat and colorectal cancer, and an increased risk of colorectal cancer with each 50-gram portion of processed meat eaten daily.
Processed meat, as defined by the IARC, “refers to meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation.” The IARC Group 1 classification puts processed meat in the same category as substances like X-ray and gamma radiation, asbestos, and benzene. Red meat, on the other hand, refers to “all types of mammalian muscle meat, such as beef, veal, pork, lamb, mutton, horse, and goat.” IARC notes that the red meat classification (IARC Group 2A) is based on “limited evidence that the consumption of red meat causes cancer in humans and strong mechanistic evidence supporting a carcinogenic effect.” Other substances in Group 2A include creosote, vinyl bromide, and PCBs.
The National Cattlemen’s Beef Association issued a quick response to the IARC report. Its news release states that science does not support the IARC’s opinion on red meat and cancer. According to the release, “A large meta-analysis, published online in May in the Journal of the American College of Nutrition, analyzed the relationship between red meat intake and risk for colorectal cancer and concluded ‘red meat does not appear to be an independent predictor of CRC risk.’” That research was conducted by epidemiologist Dominik Alexander, PhD, MSPH, on behalf of the Beef Checkoff.
Another recent study published in August by authors affiliated with Harvard Medical School, Harvard T.H. Chan School of Public Health, Dana-Farber Cancer Institute, Brigham and Women’s Hospital, Massachusetts General Hospital, Hanoi Medical University in Vietnam, and others found little evidence that higher intake of unprocessed red meat substantially increased the risk of colorectal cancer, but did observe a “significant and positive association” between processed red meat and colorectal cancer. That study, Processed and Unprocessed Red Meat and Risk of Colorectal Cancer: Analysis by Tumor Location and Modification by Time, can be found here.
The National Cattlemen’s Beef Association news release also points to disagreement within the IARC. After seven days of deliberation, IARC’s 22 experts were unable to reach a “consensus agreement” on the red meat classification and had to “settle” for a majority agreement according to the Association’s release. The release also quotes Shalene McNeill, PhD, RD as saying that “no single food has ever been proven to cause or cure cancer. The opinion by the IARC committee to list red meat as a probable carcinogen does not change that fact. The available scientific evidence simply does not support a causal relationship between red or processed meat and any type of cancer.”
This issue is clearly one to watch, and will no doubt make dinner table debates a bit more interesting.