Media outlets were abuzz this week vilifying processed and red meat after the International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization (WHO), released an opinion that processed meat should be classified as carcinogenic to humans (Group 1) based on sufficient evidence in humans that the consumption of processed meat causes colorectal cancer. The experts concluded that each 50 g portion of processed meat eaten daily increases the risk of colorectal cancer by 18 percent.
IARC also classified the consumption of red meat as probably carcinogenic to humans (Group 2A) based on limited evidence that the consumption of red meat causes cancer in humans and strong mechanistic evidence supporting a carcinogenic effect. This association was observed mainly for colorectal cancer, but associations also were seen for pancreatic cancer and prostate cancer.
The IARC Working Group considered more than 800 studies that investigated associations of more than a dozen types of cancer with the consumption of red meat or processed meat in many countries and populations with diverse diets. The most influential evidence came from large prospective cohort studies conducted over the past 20 years.
"These findings further support current public health recommendations to limit intake of meat," said Christopher Wild, director, IARC. “At the same time, red meat has nutritional value. Therefore, these results are important in enabling governments and international regulatory agencies to conduct risk assessments, in order to balance the risks and benefits of eating red meat and processed meat and to provide the best possible dietary recommendations."
The North American Meat Institute (NAMI) responded that the IARC’s conclusion “defies both common sense and numerous studies showing no correlation between meat and cancer and many more studies showing the many health benefits of balanced diets that include meat. Scientific evidence shows cancer is a complex disease not caused by single foods and that a balanced diet and healthy lifestyle choices are essential to good health."
“IARC’s decision simply cannot be applied to people’s health because it considers just one piece of the health puzzle: theoretical hazards," said Betsy Booren, NAMI vice president of scientific affairs. “Risks and benefits must be considered together before telling people what to eat, drink, drive, breathe, or where to work."
The National Cattlemen’s Beef Association also responded: “There are a constellation of factors that are associated with the probability of getting cancer, which include age, genetics, socioeconomic characteristics, obesity, lack of physical activity, where you grew up, alcohol consumption, smoking, and even your profession," said Dominik Alexander, principal epidemiologist, EpidStat Institute, who conducted the research on behalf of the Beef Checkoff. “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. 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."