International Agency for Research on Cancer Evaluates Red and Processed Meat - Backgrounder

by Shalene McNeill, Ph.D., R.D., Executive Director, Human Nutrition Research and Joe Hansen, Director, National Cattlemen’s Beef Association, a contractor to the Beef Checkoff

Summary

The potential relationship between red meat consumption and cancer risk continues to be a controversial topic debated in the scientific community, among authoritative bodies, and via social and traditional media channels. In November 2014, the World Health Organization’s (WHO) International Agency for Research on Cancer (IARC) announced it will be evaluating red and processed meat with regard to carcinogenicity. A working group of international cancer research experts are currently reviewing the available evidence regarding any associations between red and processed meat consumption and the risk of developing various types of cancer. In October 2015, this group will convene for an eight-day meeting to come to a collective decision on the potential carcinogenicity of red and processed meat. Following this meeting, IARC will publish a final decision (referred to as an IARC monograph) regarding the classification of red and processed meats as a carcinogen and the degree of certainty (definite, probable, possible, not classifiable, probably not) supported by the evidence. The exact timing of the Monograph release is currently unknown, though anticipated to be sometime in 2016. The Beef Checkoff is working to prepare research summaries and scientific references for submission to IARC, including comprehensive, systematic evidence reviews to ensure that the balance of evidence is considered by the Working Group. Given that cancer is a topic of public interest and an issue that hits very close to home for many Americans, the Beef Checkoff is also developing education and communication resources that can provide important context and balanced perspectives on the role of diet and lifestyles in the development of cancer for both consumer influencers (registered dietitians, medical professionals and academics) as well as general consumer audiences. As IARC is a well-respected global agency, the evaluation presents an opportunity for the beef community to dispel the deep-seeded myth that red meat independently plays a role in the development of cancer.

Background

In an effort to reduce the incidence and healthcare cost burden associated with cancer, regulatory and risk assessment agencies commonly evaluate the available evidence regarding various agents, e.g. chemicals, pollutants and ingredients, to determine the likelihood that they may cause cancer or, in other words, if they are carcinogenic. Groups that conduct such evaluations, independently and collaboratively, include global agencies such as the World Health Organization’s (WHO) International Agency for Research on Cancer (IARC), World Cancer Research Fund International, and national agencies such as the European Food Safety Authority and American Institute for Cancer Research.

Internationally, IARC is known for its Monographs, which are a series of scientific reviews that seek to identify individual compounds and substances – such as chemicals, pollutants – and more complex exposures such as occupational hazards and foods – that can increase cancer risk. Historically and collectively, the IARC Monographs, sometimes referred to as WHO's “Encyclopedia of Carcinogens,” have reviewed more than 900 agents. Through this process, IARC has classified 400 of these agents as “known”, “probable” or “possible” carcinogens.

There are five possible classifications for exposures evaluated by IARC:

  • Group 1 Carcinogenic to humans     
  • Group 2A Probably carcinogenic to humans   
  • Group 2B Possibly carcinogenic to humans   
  • Group 3 Not classifiable as to its carcinogenicity to humans         
  • Group 4 Probably not carcinogenic to humans

Since the Monographs began in 1972, IARC traditionally has focused its research efforts on chemicals and pollutants; however, on occasion IARC has evaluated the cancer risk of specific foods, including coffee, tea, amaranth, salted fish, pickled vegetables and, on two separate occasions, alcohol (1988, 2010). Alcoholic beverages are classified as Group 1 carcinogens, coffee is a Group 2B carcinogen, and tea has not been classifiable as to its carcinogenicity to humans (Group 3). It is difficult to use these previous food-related classifications as a baseline for potential traditional and social media coverage of a beef classification because these are not contemporary examples. One factor making it difficult to extrapolate potential media coverage is the explosive growth of social media. In 2010, Twitter was only three years old and had just 54 million active users, compared to today with more than 302 million active users. Additionally, these foods do not represent a category of foods that have long been recommended as part of a healthful diet by federal agencies, such as the U.S. Department of Agriculture. For all of these reasons, it is difficult to compare the potential impact of a beef monograph to any other food. 

In November 2014, IARC announced it will be evaluating red and processed meat with regard to carcinogenicity. The Red Meat and Processed Meat Monograph (Monograph 114) marks the first time that IARC has chosen to analyze a broader food category rather than specific foods. Evidence evaluation will be completed by a Working Group of cancer research experts. IARC issued a call for experts to participate in the red and processed meat Working Group earlier this year, a public announcement of the Working Group members is expected at any time. These Working Group members are currently reviewing the available evidence regarding the risk of developing any cancer and the association with red and processed meat consumption. In October, this group will convene for an eight-day meeting to come to a collective decision on the potential carcinogenicity of red and processed meat. While the public is not invited to this meeting, a very small number of observers, selected by a nomination and review process, are allowed to attend. Observers are tasked with ensuring that all published information and scientific perspectives are considered during the meeting. The Beef Checkoff has nominated several technical experts and independent scientists to be considered as Observers. Following their meeting, IARC will publish a final decision (aka the IARC Monograph) regarding the classification of red and processed as a carcinogen and with what degree of certainty (definite, probable, possible, not classifiable, probably not) the available evidence supports this classification. The final monograph will be published in the scientific journal The Lancet sometime the following year and be made available on the IARC website.

IARC is considered an authoritative body by many regulatory agencies, meaning there is potential for significant implications if red and processed meat consumption is found to be carcinogenic to humans including the potential for “warning” labels, advisories from government agencies and possible changes to dietary guidance issued by individual countries. More information from IARC is available.

Discussion

The evidence base for diet and cancer relies on observational data – a type of research that reports observed associations between exposures (i.e. diet or dietary components) and outcomes (i.e. cancer) but cannot establish cause and effect relationships. In contrast, randomized controlled clinical trials are considered gold standard evidence that can be used to determine cause and effect relationships but these studies are less common in cancer research because the time period to develop cancer can be quite long. Many cancers develop 10-20 years after exposure thus requiring prolonged research trials that are costly and prone to subject non-compliance and drop out. Understanding whether or not red meat intake is independently associated with cancer is further complicated by imprecise meat definitions and confounded by the overall dietary pattern in which red meat is consumed.   
Over the last 10 years, the Beef Checkoff has extensively reviewed the research on red meat and cancer, and the independent scientists who have conducted this research have consistently concluded “the totality of the available scientific evidence is not supportive of an independent association between red meat or processed meat and cancer.”

As part of a public consultation, IARC has requested published evidence, including original epidemiological research, cancer bioassays, mechanistic data, systematic reviews, meta-analyses, and relevant, publicly-available government reports, which will be used in their evaluation of red and processed meat. The Beef Checkoff has already submitted a comprehensive overview of the observational evidence surrounding red and processed meat and cancer risk, including a recent Beef Checkoff-funded meta-analysis. This meta-analysis, published online in May in the Journal of the American College of Nutrition, analyzed the relationship between red meat intake and risk for colorectal cancer and concluded no observable relationship. The full paper can be found here.

The most recent, unrelated, example of an IARC decision has been the classification of glyphosate – a key ingredient in Round-Up – as a Class 2A carcinogen. Much of the news coverage focused on what a Class 2A carcinogen actually means to consumers, including a “whiteboard” YouTube video and NPR stating: “…IARC is saying that glyphosate probably could cause cancer in humans, but not that it probably does.” Overall, the consumer is confused as to what science they can believe and what science they can dismiss. We know from Beef Checkoff-funded research that there is a segment of “information seeking” consumers who are actively looking for information on these complex issues in order to make a decision and that they “googling” for much of this information. At the same time, they’re looking to influencers—registered dietitians, medical doctors and others—for advice. That is why it is so important to balance the conversation offering up both sides of the story and having a strong basis in science to back-up our story, thereby allowing the consumer to make the ultimate, informed decision. 

As a science-based, trusted leader in nutrition research, the Beef Checkoff is working to ensure a balanced perspective on the evidence related to total diet, red meat and cancer. As such, the Beef Checkoff is working to prepare a series of research summaries and scientific references covering a broad array of topics relevant to the evidence evaluation process for submission to IARC. Information will be available to interested researchers, register dietitians and many consumer-facing resources to help put this complex topic into perspective. This will include fact sheets, background materials, videos and blog posts publically available on the Beef Checkoff-funded website, FactsAboutBeef.com.

Conclusions

As IARC is a well-respected global agency, their decision regarding the carcinogenicity of red and processed meat has far-reaching implications. The challenge for the beef community in this process is to dispel the deep-seeded myth that red meat plays an independent role in the development of cancer. In collaboration with other industry trade groups and associations, the Beef Checkoff is actively participating in this process by contributing quality research on the topic to the body of evidence that will be reviewed by IARC and is concurrently engaging with key thought leaders and consumer influencers to continue demonstrating the role of beef in a healthy diet.

For detailed information on the epidemiological evidence on red meat and processed meat consumption and cancer, review this technical summary

Additional Resources

Tags: Beef Issues Quarterly, Issues Updates, Summer 2015

June 18, 2015