WHO report says eating processed meat is carcinogenic: Understanding the findings

Late in October the World Health Organization (WHO)’s International Agency for Research on Cancer (IARC) announced that consumption of processed meat is “carcinogenic to humans (Group I ),” and that consumption of red meat is “probably carcinogenic to humans (Group 2A).”

The report differentiates the two meats as follows:

  • Processed meat – meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavor or improve preservation
  • Red meat – unprocessed mammalian muscle meat such as beef, veal, pork, lamb, mutton, horse and goat meat

The WHO analysis on red and processed meat and cancer risk was consistent with a research commissioned by Cancer Council Australia that was released earlier that month. The study found that 2600 bowel cancer cases each year could be attributed to excess red and processed meat consumption.

Unfortunately it seems that rather than encouraging a wave of positive change towards a healthier lifestyle and diet, the findings created a media frenzy. It seems like especially here in Australia rather than being relieved that progress in the cancer prevention sphere had been made, many tried to play down the risks and ridicule the recommendations provided.

Australia’s Agriculture Minister, Barnaby Joyce, quickly dismissed the report by commenting:  “If you got everything that the WHO said were carcinogenic and took it out of your daily requirements, well, you are kind of heading back to a cave.” Joyce said he did not think Australians would be concerned about the report’s findings. It may, however, cause some unease in our beef industry, which is worth more than $12 billion.

Why the prosperity of our beef industry should be valued more than our own health, is beyond me to comprehend.

I think the report finding’s should not be taken lightly. Our health is our own responsibility and the link between lifestyle, diet and cancer is so strong that cannot be ignored anymore.

The Harvard T.H. Chan School of Public Health recently published this interview between Kana Wu, a member of the International Agency for Cancer Research (IARC) Monograph Working Group for this report and a Senior Research Scientist in their Department of Nutrition.

I am reporting it here because I feel it really clarifies some of the points of the WHO report. It also addresses questions about “organic”, “nitrate-free” and other so-called “healthier” options.


The IARC Working Group said red meat is “probably” carcinogenic, but several studies showed no clear association. Can you explain why it’s probably carcinogenic?

In large population studies, but not all of them, greater red meat consumption has been associated with higher risk of colorectal cancer. Although these studies were not entirely consistent, results of laboratory studies led the IARC working group to conclude that red meat is probably carcinogenic.

Some reports in the media, particularly those from the meat industry, promote red meat consumption as part of a healthy and balanced diet. Is this true?

While it is true that red meat has nutritional value – it is rich in protein, minerals and vitamins (e.g., vitamin B12) – many studies have also shown that high consumption of red meat can increase the risk of colorectal cancer, heart disease, diabetes, and other chronic diseases, and may lead to higher risk of dying of those diseases (when compared to other good sources of protein, such as poultry, fish or legumes).  Thus, much evidence suggests that an optimally healthy diet would be low in red meat.

The IARC/WHO classified processed meat as a Group 1 carcinogen, the same category as tobacco smoking and asbestos. Some media reports have indicated that eating bacon or hot dogs is as bad as smoking. Is this true?

It has been known for a while that high consumption of red or processed meat can adversely affect health, including raising risk of colorectal cancers and some other cancers. So the conclusions drawn by the IARC Working Group are consistent with what we already know. However, the way the media has reacted to last week’s IARC/WHO announcement has created a lot of confusion and this requires clarification.

Smoking vs. high consumption of processed meat

Even though smoking is in the same category as processed meat (Group 1 carcinogen), the magnitude or level of risk associated with smoking is considerably higher (e.g., for lung cancer about 20 fold or 2000% increased risk) from those associated with processed meat – an analysis of data from 10 studies, cited in the IARC report showed an 18 percent increased risk in colorectal cancer per 50g processed meat increase per day. To put this in perspective, according to the Global Disease Burden Project 2012, over 34,000 cancer deaths per year worldwide are attributable to high processed meat intake vs. 1 million deaths per year attributable to tobacco smoke.

 High consumption of red or processed meat also increases risk of other chronic diseases and mortality

It is important to keep in mind that the above estimates pertain to cancer deaths only. It is well known that besides increasing the risk of some cancers, high red and processed meat intake can also increase risk of other chronic and potentially life threatening diseases such as coronary heart disease, stroke and type II diabetes compared to other protein sources such as poultry, legumes and fish. Our group at the Harvard T.H. Chan School of Public Health and theHarvard Medical School and others have also found higher rates of total mortality with higher intake of red or processed meat. In fact, according to 2013 data from the Global Burden of Disease Project, the number of total deaths (including deaths from cardiovascular disease or diabetes and colorectal cancers) attributable to a diet high in processed meat was 644,000.

Some people purchase “nitrate-free” processed meats, a fairly new food trend. Could that help make processed meat less carcinogenic?

So-called “nitrate-free” processed meats are often preserved with celery juice, a plant rich in nitrate. The source of nitrate added for meat preservation will likely not matter. Furthermore, processed meats can also contain other carcinogenic compounds such as PAHs which can be formed during smoking of meat (e.g. salami). Processed meats, particularly those containing red meat also contain heme iron, which can enhance the formation of carcinogenic compounds (NOCs) in the body. Until we know more about the exact mechanisms underlying the relationship between processed meat and cancers, it is best to treat those nitrate-free processed meats the same as any other processed meats and limit intake.

 How about chicken or turkey hot dogs, or turkey bacon – are those safer to eat than bacon or hot dogs containing red meats such as beef or pork?

Chicken and turkey hot dogs and turkey bacon may also contain preservatives such as nitrates. However, those meats contain less heme iron than processed meats made from red meats. A good alternative is to replace red or processed meat with unprocessed, fresh chicken or turkey, which is a good source of protein, vitamins and minerals. Also to be considered are nuts, peanuts, soy, and legumes, such as hummus.

Are processed meats made from so-called “organic” meats safer?

Processed meats made from so-called “organic meats” are generally treated with natural nitrate such as celery juice or smoked as well. At this point there is insufficient data to conclude whether those meats are safer than the “non-organic” meats.

Are there any specific types of processed meats that should be avoided more than others?

IARC evaluated consumption of total processed meat, not one specific type of meat, because data relating specific subtypes of processed and red meat to risk of cancers are currently limited. Therefore, it is not yet possible to draw a conclusion on whether specific types of meats are safer. Overall, it is best to limit consumption of any processed meat.

How much red or processed meat, if any, can I eat? What do you recommend?

Studies have shown that the higher the intake of processed meat, the higher the risk of colorectal cancers and other chronic diseases (dose-response). This does not mean you have to cut out all red and processed meats from your diet. In our Healthy Eating Platewe suggest avoiding processed meat and consuming red meat occasionally at most.   Ideally, we should be thinking of red meat as we do lobster, having it for a special occasion if we like it. This is how red meat is consumed in many traditional eating cultures, such as the Mediterranean diet. Other organizations have also recommended limiting consumption of red meat for better health, including the American Heart Association, the World Cancer Research Fund (WCRF) and the American Cancer Society. For example, the WCRF recommends to limit intake of red meat to 500g per week and to avoid processed meat.

You can read the full interview here.

Source: The Nutrition Source

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