The identification of processed meat and red meat as cancer hazards buttresses public health recommendations to limit meat consumption, said the director of the WHO agency that investigated meat. The International Agency for Research on Cancer classified processed meat as “carcinogenic to humans” – its strongest ranking – and red meat as “probably carcinogenic to humans,” the second-strongest ranking. The meat industry disputed the evidence and accused IARC of scare-mongering.
Consumption of meat, such as beef, pork, mutton, horse or goat, is associated with an increased risk of colorectal cancer although the overall risk of the disease is small, said IARC.
“These findings further support current public health recommendations to limit intake of meat. At the same time, red meat has nutritional value,” said IARC director Christopher Wild in a statement. “Therefore, these results are important in enabling governments and international regulatory agencies to conduct risk assessments, in order to balance risks and benefits of eating red meat and processed meat and to provide the best possible dietary recommendations.”
Agriculture Secretary Tom Vilsack told reporters: “The Dietary Guidelines are pretty clear. Lean meat is part of a healthy diet. That’s the science that we rely on. It’s the science that’s being reviewed now as the Dietary Guidelines are being developed and until such time as the folks who are formulating the Dietary Guidelines tell me differently, that’s the approach we are going to take.”
The USDA and the Health Department plan to issue a new edition of the guidelines before the end of 2015, more than two years after it began work on them.
An advisory committee appointed by the government recommends that the 2015 guidelines specifically advocate a diet that is “lower in red and processed meat.” The current guidelines, which were released in 2010, say only that a healthy eating pattern includes lean meats and poultry. The guidelines also recommend that diets be rich in fruits, vegetables, whole grains, low-fat dairy products and seafood while limiting salt, fat and sugar. The advisory panel for the 2015 guidelines cited moderate evidence of an association between colorectal cancer and red and processed meat.
The consumer group Center for Science in the Public Interest said the IARC’s “sound and reasoned assessment … should guide” the government in updating the Dietary Guidelines.
The American Cancer Society said it “has long recommended a diet that limits processed meat and red meat, and that is high in vegetables, fruits, and whole grains.” The World Health Organization recommends that meat-eaters moderate their consumption of processed meat.
An expert panel of 22 scientists from 10 nations reviewed more than 800 epidemiological studies for the IARC study. The large amount of data and consistent association of processed meat with colorectal cancer “in different populations … make chance, bias and confounding (factors) unlikely as explanations,” said the report, so a majority of the working group agreed there was sufficient evidence to say processed meat is carcinogenic. The studies were not as clear on red meat, so the experts decided there was limited evidence of carcinogenicity.
The working group concluded that every 50 grams, or roughly 2 ounces, of processed meat eaten daily – equal to one hot dog – increases the risk of colorectal cancer by 18 percent.
The IARC did not evaluate poultry or seafood or compare vegetarian diets with diets that include meat.
Diets high in processed meat – such as hot dogs, ham, sausage, corned beef and beef jerky – contribute to 34,000 cancer death annually worldwide, and diets high in red meat could be responsible for 50,000 deaths a year, according to Global Burden of Disease Project. Smoking is blamed for 1 million deaths a year, alcohol for 600,000 deaths and air pollution for 200,000 deaths.
House Agriculture chairman Michael Conaway, from the No. 1 cattle state of Texas, said the IARC based its conclusions on “a biased selection of studies.” The 2015 Dietary Guidelines should “promote a balanced diet with beneficial nutrients derived from a wide variety of safe and wholesome agricultural products,” he said.
The National Cattlemen’s Beef Association cited epidemiologist Dominik Alexander, who says there are myriad factors involved in cancer and therefore it was not valid to single out meat. “Studies have shown that people who consume the most red meat are the most likely to smoke, eat fewer fruits and vegetables and be overweight or obese – all of which may confound the relationship between eating red meat and risk of cancer,” said Alexander. The National Pork Producers Council also was skeptical of the level of proof available and noted that obesity and sedentary lifestyles pose a far greater risk of several types of cancer.
IARC classifies carcinogens on a five-point scale that indicates the weight of evidence that an agent is capable of causing cancer, which it calls the hazard. IARC does not measure the likelihood, which it calls risk, that cancer will occur as a result of exposure to the agent.
“The distinction between hazard and risk is important,” says IARC. The risk associated with agents given the same classification “may be very different, depending on factors such as the type and extent of exposure and the strength of the effect of the agent.”
Consumption of red meat varies throughout the world. In countries like the United States, almost everyone eats meat, while in some nations only 5 percent of the people do. High consumption of red meat is more than 200 grams a day, or 7 ounces, said the IARC report, which said there was less information available on processed meat. Americans are estimated to consume nearly 9 ounces a day of meats of all types, roughly half of which is poultry.
In May 2016, IARC is to report on “coffee, mate and very hot beverages.” On March 20, IARC listed glyphosate, the most widely used weedkiller in the world, as probably carcinogenic to humans. Monsanto, which uses glyphosate as the main ingredient in its Roundup herbicide, says the chemical is safe and is trying to convince other scientific agencies to accept its view.