WHO’s Linkage of Red, Processed Meats & Colon Cancer Challenged

By Mairead McArdle | October 28, 2015 | 3:03pm EDT


(AP photo)

(CNSNews.com) -- Some scientists in the U.S. and U.K. are challenging claims by the World Health Organization’s (WHO) cancer research agency that eating red and processed meats like steak and bacon causes colorectal cancer (CRC) in humans.

The International Agency for Research on Cancer (IARC) released its report in The Lancet Oncology Monday, labeling processed meat “carcinogenic to humans based on sufficient evidence in humans that the consumption of processed meat causes colorectal cancer.”

The report puts processed meats like bacon and sausage on par with other known Group 1 carcinogens such as asbestos, formaldehyde and tobacco.

Red meat was labeled as “probably carcinogenic to humans based on limited evidence that the consumption of red meat causes cancer in humans and strong mechanistic evidence supporting a carcinogenic effect.”

The National Institutes of Health reports that CRC accounts for 8 percent of all new cancer cases in the U.S. However, according to the Mayo Clinic, “in most cases, it’s not clear what causes colon cancer.” 

“Red meat does not appear to be an independent predictor of CRC risk,” said epidemiologist Dominik Alexander, who conducted a meta-analysis on the connection between red meat and CRC for Beef Checkoff. His study, which was partially funded by Meat & Livestock Australia, was published in May in the Journal of the American College of Nutrition

"The bottom line is the epidemiologic science on red meat consumption and cancer is best described as weak associations and an evidence base that has weakened over time,” Alexander said. “And most importantly, because red meat is consumed in the context of hundreds of other foods and is correlated with other behavioral factors, it is not valid to conclude red meat is an independent cause of cancer.”

"In the case of red and processed meat, the overall scientific evidence simply does not support their conclusion," said nutritional toxicologist James Coughlin, who has studied the connection between eating meat and cancer for 40 years, according to a press release by the National Cattleman's Beef Association.

“No single food has ever been proven to cause or cure cancer,” Shalene McNeill, the cattlemen group's executive director of nutrition research, added. “The opinion by the IARC committee to list red meat as a probable carcinogen does not change that fact.”

“Although there is epidemiological evidence for a statistically significant association between processed meat consumption and bowel cancer, it is important to emphasize that the size of the effect is relatively small, and the mechanism is poorly defined,” said Dr. Ian Johnson, emeritus fellow of the Britain’s Institute of Food Research, The Telegraph reported.

He continued: "It is certainly very inappropriate to suggest that any adverse effect of bacon and sausages on the risk of bowel cancer is comparable to the dangers of tobacco smoke, which is loaded with known chemical carcinogens and increases the risk of lung cancer in cigarette smokers by around 20-fold.”

Prof. Robert Pickard, emeritus professor of neurobiology at the University of Cardiff, referenced a 2014 updated study of more than 61,000 British men and women that found little difference in bowel cancer rates between vegetarians and meat-eaters, although meat-eaters had higher incidences of other cancers. 

“Avoiding red meat in the diet is not a protective strategy against cancer,” Pickard said. “The top priorities for cancer prevention remain smoking cessation, maintenance of normal body weight and avoidance of high alcohol intakes."

“Choosing a meat-free diet is a lifestyle choice – it is not vital for health," he stated.

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