Thursday July 27 2017

What’s in your meat?

On October 26, 2015 the International Agency for Research on Cancer (IARC) of the World Health Organization announced that it added ‘processed meat’ and ‘red meat’ to its list of Group 1 (carcinogenic to humans) and Group 2A (probably carcinogenic to humans) carcinogens, respectively.[1] This is the first time that a dietary item besides alcohol has been added to these categories. The news became an instant hot topic internationally, triggering an outbreak of fear, confusion and scepticism.

What was the rationale underlying this bold decision made by the international experts on cancer research? The IARC has five categories of carcinogenic agents, ranging from Group 1 ‘carcinogenic to humans’ to Group 4 ‘probably not carcinogenic to humans’.[2] The new additions have been made to Groups 1 and 2A, the categories associated with the highest likelihood of causing cancer development.[1] Decisions to add suspected carcinogens to the list are made by a working group of international scientific experts that evaluates the degree and quality of evidence supporting the proposed relationship.[1] In the case of processed and red meats, the link to cancer was investigated by 22 experts through the consideration of 800 studies, with the most compelling evidence coming from prospective cohort studies conducted over the past 20 years.[1]

For many, it seems strange that the IARC has suddenly taken such a bold step. After all, processed and red meats have been an essential part of the diet for thousands around the world. If they were really so harmful, surely someone would have noticed earlier? The reality is that several studies had been published over the years indicating a link between certain types of meats and risk of cancer.[3] These studies were considered by an international advisory committee last year which recommended IARC to further explore this relationship and draw an authoritative scientific conclusion.[3] Therefore, the potential risk associated with the consumption of processed and red meats has been noted for some time, but it is only now making an appearance in the media.

At this stage, it is clear that this decision is well supported by available scientific literature. However, where do we go from here? The first step is to ensure that the public is well-informed on this matter so that people can make safe decisions regarding their health. For this, the presentation of this relationship is critical to maintain delicate balance of avoiding both alarm and ignorance. A number of media articles have presented this relationship in a misleading way by drawing parallels between processed meats and other Group 1 carcinogens such as asbestos and tobacco smoking.[4,5] The IARC has clarified that inclusion in Group 1 is determined by the degree of evidence supporting the relationship, not the risks associated with the carcinogenicity.[3] Therefore, Group 1 carcinogens are not the most ‘deadly’ in the sense that minimal exposure can lead to develop of cancer. Instead, they are the carcinogens for which the evidence appears most compelling and definitive. Despite this, many media articles continue to misinterpret the relationship, fuelling public fear and misconception. Governments and public health agencies are still in the process of developing a plan to educate the public on how to respond to this news and understand their role as individuals affecting change in their own health.

While processed and red meats are established as carcinogens, research into the underlying science is far from over. This is just the start of a new avenue in healthcare research, ranging from efforts to understand the biochemical mechanisms of these carcinogens to efforts to assess their effects on public health and policy-making. The IARC is now in the process of evaluating current evidence to understand the role of meat-cooking techniques.[3] Nutritional guidelines in upcoming years may reflect these recent discoveries, and physicians around the world may be changing their practice in making dietary recommendations. For some, the news that many favourite meat dishes may be increasing their risk for cancer could be daunting, but in the scientific community, it has accelerated the drive to understand the factors underlying our health and wellbeing.

By Fizza Manzoor



1.     IARC. Press Release: IARC Monographs evaluate consumption of red meat and processed meat [Internet]. World Health Organization; 2015 [cited 2015 Oct 28]. Available from: https://www.iarc.fr/en/media-centre/pr/2015/pdfs/pr240_E.pdf

2.     IARC. Agents classified by the IARC Monographs, Volumes 1-114 [Internet]. International Agency for Research on Cancer. [cited 2015 Oct 28]. Available from: http://monographs.iarc.fr/ENG/Classification/

3.     IARC. Q&A on the carcinogenicity of the consumption of red meat and processed meat [Internet]. World Health Organization; 2015 [cited 2015 Oct 28]. Available from: http://www.iarc.fr/en/media-centre/iarcnews/pdf/Monographs-Q&A_Vol114.pdf

4.     Boseley S. Processed meats rank alongside smoking as cancer causes – WHO. The Guardian [Internet]. 2015 Oct 26 [cited 2015 Oct 28]; Available from: http://www.theguardian.com/society/2015/oct/26/bacon-ham-sausages-processed-meats-cancer-risk-smoking-says-who

5.     Processed meats do cause cancer – WHO. BBC [Internet]. 2015 Oct 26; Available from: http://www.bbc.com/news/health-34615621


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The Meducator is McMaster University’s undergraduate Health Sciences Journal. It publishes pieces that critically address current issues with a high degree of scientific rigor, but in a way that is accessible to a broad audience.


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