On October 26, 2015, The World Health Organization announced that processed meat is carcinogenic, and red meat probably is too.1 They defined processed meat as ‘meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation’. Before you decide to pass on the bacon or defiantly include it in every meal, let’s break down the report to understand the risk.
The International Agency for Cancer Research (IARC) is the specialized cancer agency of the World Health Organization. The IARC is the body that evaluated the research to come to conclusions regarding the cancer-causing properties of processed and red meat. Over the course of a week, 22 experts from 10 countries evaluated more than 800 epidemiological studies on the relationship between meat consumption and cancer.2 Of those studies, 700 looked at red meat, while 400 considered processed meat. After evaluating the evidence, experts concluded that there was sufficient data in support of the causal relationship between processed meat and colon cancer2.
The IARC ranks substances on a 4-point scale from carcinogenic to probably not carcinogenic to humans3. Processed meat is now classified as a Group 1 carcinogen, meaning that the expert group concluded that processed meat causes cancer – specifically, colon cancer2. They also classified red meat as a Group 2A probable carcinogen, which means that there is limited epidemiological evidence (from studies) and strong mechanistic evidence for this association.
To date, the IARC has evaluated 985 substances on their potential carcinogenicity in humans. There are currently 118 agents classified as Group 1 carcinogens to humans. These include substances such as alcohol, asbestos, tobacco, and now processed meat3. However, this does not mean that tobacco and processed meat are equally dangerous. Epidemiologists use specific measures to quantify the risk from each of these substances – see the below table.
|Measure||Definition||Eg: processed meat and colon cancer||Eg: smoking and lung cancer|
|Population attributable risk||The amount of disease occurring in a population that can be attributed to the exposure of interest||Causes 34,000 deaths per year globally2||Causes 1,350,650 deaths per year globally4|
|Population attributable fraction||The proportion of disease occurring in a population that can be attributed to the exposure of interest||Estimated to be 15-20% – this means that ~18% of all colorectal cancer cases are due to a diet high in processed meat5||Approximately 85%|
Adapted from Webb and Bain, 2011.
So we can clearly see that although both tobacco and processed meat are carcinogenic, tobacco causes more mortality (death) than processed meat does. Furthermore, the exact mechanism(s) through which processed meat leads to the development of cancer is unclear – it could be that the risk is modified by cooking method, or demographic characteristics of individuals such as age or sex. Based on the recent evaluation, the IARC has estimated that eating a daily portion of 50g (2 bacon rashers) of processed meat increases the risk of colon cancer by 18%2.
What does this mean for the average Joe? Each individual will need to consider what is important to him or her. While it is advisable to cut down on processed meat and save the bacon for special occasions, eating red meat does have nutritional benefits. I personally will follow the common sense adage, ‘everything in moderation.’
- International Agency for Research on Cancer. (October 26, 2015). Press Release N. 240: IARC monographs evaluate consumption of red meat and processed meat. Retrieved from https://www.iarc.fr/en/media-centre/pr/2015/pdfs/ pr240_E.pdf
- International Agency for Research on Cancer. (October 2015). Q&A on the carcinogenicity of the consumption of red meat and processed meat. Retrieved from http://www.iarc.fr/en/media-centre/iarcnews/pdf/Monographs-Q&A_Vol114.pdf
- International Agency for Research on Cancer. (October 2015). IARC monographs on the evaluation of carcinogenic risks to humans. Retrieved from http://monographs.iarc.fr/ENG/Classification/index.php
- World Health Organization. (February 2015.) Cancer. Retrieved from http://www.who.int/mediacentre/factsheets/fs297/en/
- Nagle, C.M., Wilson, L.F., Hughes, M.C.B., Ibiebele T., Miura, K. et al. (2015). Cancers in Australia in 2010 attributable to the consumption of red and processed meat. Australian and New Zealand Journal of Public Health, 39(5):429-433.
- Parkin, D.M. (2011). Tobacco-attributable cancer burden in the UK in 2010. British Journal of Cancer, 105(Supplement 2):S6-S13.
- Webb, P. & Bain, C. (2011). Essential Epidemiology: An introduction for students and health professionals. Cambridge: Cambridge University Press.
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