WHO classifies red meat 'probably carcinogenic,' links it to higher colon cancer risk

7 key questions and answers that will help you understand latest findings on red and processed meats
Processed meats
An international report released today shows consuming red meat and processed meats, such as sausages, causes a higher risk of cancer. Stock photo by Brett Mulcahy / Feature Pics

Beef is what’s for dinner — for some eaters — but an international report asserted Monday that eating red meat causes a higher risk of colorectal cancer and malignancies in the prostate and pancreas.

A working group of 22 health experts from 10 countries, convened by the World Health Organization, reviewed 800 studies on cancer and said the data “suggest that the risk of colorectal cancer could increase by 17 percent for every 100-gram portion of red meat eaten daily.”

In fact, after reviewing the scientific literature, the WHO working group classified “the consumption of red meat 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.”

Hot dog lovers also won’t be happy with this WHO report. Using the study data, the authors estimated that “every 50-gram portion of processed meat eaten daily increases the risk of colorectal cancer by 18 percent.” Examples of “processed meats” listed by the group include hot dogs, sausages, corned beef and beef jerky plus “canned meat.”

“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,” says Dr. Kurt Straif, head of the International Agency for Research on Cancer (IARC), part of WHO. “In view of the large number of people who consume processed meat, the global impact on cancer incidence is of public health importance.”

For weekend tailgaters firing up brats on the grill, or for those with a steak-loving soul, what does this all mean?

Here are seven key questions — accompanied by answers from the WHO report and from Dr. Marian Neuhouser, a nutritional epidemiologist at Fred Hutchinson Cancer Research Center, and Dr. John D. Potter, a Fred Hutch public health sciences researcher whose work includes cancer prevention with an emphasis on colon cancer.

Q: Should I stop eating red meat and processed meat, or reduce my consumption?

A: IARC: Eating meat has known health benefits. Many national health recommendations advise people to limit intake of processed meat and red meat, which are linked to increased risks of death from heart disease, diabetes and other illnesses.

Potter: The IARC group made no recommendations.  My own view is that the evidence suggests eating no processed meat and as little red meat as can be achieved without causing distress and tension in one's household.  

There are many other reasons why we should lower our meat consumption, including the associated high fat intake and its effect on cardiovascular risk and including the impact on the planet: Cattle account for a large amount of greenhouse gas; there is high and continuing loss of forest, including rain forest to cattle ranching. … Establishing one meatless day a week is a great start.

Neuhouser: The findings are very similar to the Scientific Report of the 2015 Dietary Guidelines Advisory Committee, of which I was a member. About three servings or less a week of any red meat is what we would recommend. This includes beef, pork, and lamb.

Q: Does organic, grass-fed or free-range red meat pose a smaller cancer risk when compared to equal consumption of traditionally raised red meat?

A: Potter: (There’s) no data (available to support this) but I would doubt if there is much difference in relation to health and cancer risk. However, these practices are better for the planet.

Q: What types of meat do you define as “red meat?”

A: IARC: Red meat refers to all mammalian muscle meat, including beef, veal, pork, lamb, mutton, horse, and goat.

Q: Is eating poultry or fish healthier than eating red meat?

A: IARC: The cancer risks associated with consumption of poultry and fish were not evaluated.

Potter: … At present, we have fewer data … but, yes, in many studies where both red meat and chicken and fish have been evaluated, chicken and fish are often associated with a lower risk than red and processed meat.

Q: Do cooking methods for red meats or processed meats make them potentially more or less carcinogenic to people?

IARC: Cooking at high temperatures or with the food in direct contact with a flame or a hot surface, as in barbecuing or pan-frying, produces more of certain types of carcinogenic chemicals (such as polycyclic aromatic hydrocarbons and heterocyclic aromatic amines). However, there were not enough data for the IARC Working Group to reach a conclusion about whether the way meat is cooked affects the risk of cancer.

Potter: …Cooking at high temperature contributes, but I am not sure it can be well quantified at present. Total amount seems to be the strongest predictor.

Q: Why are processed meats considered less healthy? It is because they contain less-desirable parts?

Neuhouser: The published studies have not disentangled that minutiae, but processed meats are higher in fat, very high in sodium, used in the processing process, and often the curing agents, such as nitrites, have been shown to be detrimental. Preparation methods may also play a role, such as grilling to the point of charring or frying.

Potter: No, the evidence for processed meat is just clearer. I doubt if the parts in a lot of processed meat are, in many cases, any less desirable than the parts that constitute hamburger.

IARC: This evaluation by IARC reinforces a 2002 recommendation from WHO that people who eat meat should moderate the consumption of processed meat to reduce the risk of colorectal cancer. Some other dietary guidelines also recommend limiting consumption of red meat or processed meat, but these are focused mainly on reducing the intake of fat and sodium, which are risk factors for cardiovascular disease and obesity.

Q: What makes red meat and processed meat increase the risk of cancer?

IARC: Meat consists of multiple components, such as haem iron. Meat can also contain chemicals that form during meat processing or cooking. For instance, carcinogenic chemicals that form during meat processing include N-nitroso compounds and polycyclic aromatic hydrocarbons. Cooking of red meat or processed meat also produces heterocyclic aromatic amines as well as other chemicals including polycyclic aromatic hydrocarbons, which are also found in other foods and in air pollution. Some of these chemicals are known or suspected carcinogens, but despite this knowledge it is not yet fully understood how cancer risk is increased by red meat or processed meat.

Join the conversation. Talk about this story on Fred Hutch’s Facebook page.

Solid tumors, such as those of the colon, are the focus of Solid Tumor Translational Research, a network comprised of Fred Hutchinson Cancer Research Center, UW Medicine and Seattle Cancer Care Alliance. STTR is bridging laboratory sciences and patient care to provide the most precise treatment options for patients with solid tumor cancers.

Bill Briggs is a former Fred Hutch News Service staff writer. Follow him at @writerdude. Previously, he was a contributing writer for NBCNews.com and TODAY.com, covering breaking news, health and the military. Prior, he was a staff writer for The Denver Post, part of the newspaper's team that earned the Pulitzer Prize for coverage of the Columbine High School massacre. He has authored two books, including "The Third Miracle: an Ordinary Man, a medical Mystery, and a Trial of Faith." 

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