The International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) today classified bacon, sausages, and other processed meats as cancer causing, joining items like cigarettes, asbestos, and alcohol. Additionally, IARC included the consumption of red meat in a lower risk category of “probably carcinogenic to humans.” The decision was made after 22 experts from 10 nations looked at data from both human and animal studies that suggested a correlation. Red meat is the first food that IARC has evaluated for its carcinogenic risk.

IARC said the red meat classification was based on “limited evidence” that the consumption of red meat causes cancer in humans and “strong mechanistic” evidence supporting a carcinogenic effect. The association, according to IARC, was observed mainly for colorectal cancer, but associations were also seen for pancreatic cancer and prostate cancer.

Processed meat, on the other hand, was classified as carcinogenic to humans, based on "sufficient evidence" in humans that the consumption of processed meat causes colorectal cancer. The experts concluded that each 50 gram portion of processed meat eaten daily increases the risk of colorectal cancer by 18%.

“For an individual, the risk of developing colorectal cancer because of their consumption of processed meat remains small, but this risk increases with the amount of meat consumed,” said Dr. Kurt Straif, head of the IARC Monographs Program. “In view of the large number of people who consume processed meat, the global impact on cancer incidence is of public health importance.”

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 Dr. Christopher Wild, director of 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.”

Dr. Dominik Alexander, principal epidemiologist at the EpidStat Institute, said the basis of the IARC finding is that of a meta-analysis, which, while such an approach serves a purpose in bringing together data, it is not necessarily without bias, specifically when one considers the quality and accuracy of the research being considered.

Alexander also noted that dietary studies are tricky in and of themselves as they are often based on self-reported, food frequency questionnaires where those being surveyed are asked to recall what specifically they consumed throughout a year’s time. Often ignored in these types of recall studies, he noted, is how the food was cooked and how much was consumed.

In the same sense, cancer occurs over a long period with some triggers being 20-30 years ago. Until very recently, Alexander said, most diet-based studies haven’t gone back nearly that far. Focusing on the last few years of an event that started decades earlier just doesn’t lend itself to the most accurate determinate of cause, Alexander said.

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The North American Meat Institute (NAMI) called the decision a “dramatic and alarmist overreach.”

“Red and processed meat are among 940 substances reviewed by IARC found to pose some level of theoretical ‘hazard.’ Only one substance, a chemical in yoga pants, has been declared by IARC not to cause cancer,” said Barry Carpenter, NAMI president and chief executive officer.

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, he added.

“If this is actually IARC’s decision it simply cannot be applied to people’s health because it considers just one piece of the health puzzle: theoretical hazards. Risks and benefits must be considered together before telling people what to eat, drink, drive, breathe, or where to work,” he said.

IARC evaluates the cancer-causing potential by placing them into one of the following groups:

·         Group 1: Carcinogenic to humans

·         Group 2A: Probably carcinogenic to humans

·         Group 2B: Possibly carcinogenic to humans

·         Group 3: Unclassifiable as to carcinogenicity in humans

·         Group 4: Probably not carcinogenic to humans

The latest decision from IARC classified processed meat as Group 1 and red meat as Group 2A.

The American Cancer Society (ACS) said the IARC lists themselves say nothing about how likely it is that an agent will cause cancer.

“Carcinogens do not cause cancer at all times, under all circumstances,” ACS explained. “Some may only be carcinogenic if a person is exposed in a certain way (for example, swallowing it as opposed to touching it). Some may only cause cancer in people who have a certain genetic makeup. Some of these agents may lead to cancer after only a very small exposure, while others might require intense exposure over many years.”

Even if a substance or exposure is known or suspected to cause cancer, ACS said this does not necessarily mean that it can or should be avoided at all costs.

IARC, headquartered in Lyon, France, operates as part of WHO. Three times a year, IARC forms working groups to evaluate how something (like certain occupational chemicals, etc.) impacts the risk of cancer in people.