True or false: processed meat causes cancer

The World Health Organization (WHO) made an official statement linking the consumption of red and processed meat with cancer last Monday. Well, that’s what all the social media links and clickbait all over the web would have you believe. For example, there’s this fear-mongering headline from The Guardian that blares, “Processed Meats rank Alongside Smoking as Cancer Cause,” or this super intellectual post  from CNN:

CNN

Courtesy of CNN via Facebook

Pieces like this do little to educate readers on actual risks. Instead of allowing a reader to take in facts and compose an informed opinion, headlines and content of “science” articles are formulated to draw clicks, likes and shares, so they have to be catchy and controversial.  Even this article from the normally balanced The Associated Press does little to explain the facts rather than just publish scary numbers that demonize red and processed meats.

The report was done by the International Agency of Research into Cancer (IARC), a branch of World Health Organization. The press release says that the IARC has “classified the consumption of red meat as probably carcinogenic to humans (Group 2A), based on limited evidence that the consumption of red meat causes cancer in humans and strong mechanistic evidence supporting a carcinogenic effect,” and “Processed meat was classified as carcinogenic to humans (Group 1), based on sufficient evidence in humans that the consumption of processed meat causes colorectal cancer.”

To break it down the effect down into tangible numbers, the study looks at additional 50-gram portions of processed meat. Each additional portion in a person’s daily diet has been associated with an 18 per cent increased risk of developing cancer.

So how should you, healthfully worried, and careful, reader approach understanding of these daunting claims? Let’s break this down: first of all, we have to understand the carcinogen classification system is using, which is pretty confusing. The next major concern is sample size and methodology. This refers to how many people were involved in the study and how the study was actually done, and finally what these numbers really mean in everyday life.

Courtesy of Unsplash

So processed meat has been put into Group One, things that are definitely  carcinogenic to humans. This category is for products that IARC knows to be definite carcinogens: smoking, alcohol, etc. Fine, no one thought bologna was healthy, no arguments there. But then all red meat is classified as Group 2A, a category listed as  probable carcinogenic to humans.

That’s cool, but it’s important to note that there’s another group, classified as Group 2B, that lists possible carcinogenic. It’s confusing firstly because there is barely a difference.

But here’s the big thing that most coverage on this report have missed: These groups do not evaluate the degree of risk for each product but rather that strength of the evidence. So no, processed meats are not necessarily as dangerous as smoking, but the study shows the same amount of evidence that the two are carcinogenic. This article from The Atlantic explains that “[t]wo risk factors could be slotted in the same category if one tripled the risk of cancer and the other increased it by a small fraction.”

Rebecca Wood Headshot

A photo of Rebecca Wood (Brittany Ferreira/ Ryersonian Staff)

Beyond convoluted terms and mysterious wording you should want to know about the study itself. Who did the study? Who funded it (yes, it can affect the relative outcome), how big was the sample size, what is the margin of error, are there other factors that couldn’t have been controlled for? With this particular story we have to realize that there are many, many risk factors associated with developing cancer. So, as this article eloquently asked, we’ve got to wonder, is processed meat the maker or the marker of an unhealthy person? In other words, be sure to take into account the lifestyle of your average processed-meat-eater (on average less active, more likely to smoke and higher BMI).

Last but not least, do your math homework, people. The original study notes (while many of the publications covering the story did not) that these carcinogenic associations were mainly observed for colorectal cancer. According to numbers from the World Cancer Cancer Research Fund International, 1.4 million people will develop colorectal cancer at some point their lives. The IARC study states that by eating 20 grams of processed meat per day, a person is 18 per cent more likely to develop colorectal cancer. That’s 252 thousand more people per year which means less that 4 more people out of every 100,000 people could be affected. Obviously there are other factors that can affect how likely or unlikely a person is to develop cancer, family history and lifestyle to name a few, so these stats should be taken as an approximation.

Needless to say, just be wary of articles that overly simplify, you can almost always rightly assume that there’s more to a story, particularly those which start off with such provocative, slap-you-in-the-face headlines. A good place to start when you see a claim like this one is to read the actual study and check facts, check your facts and use critical thinking before retweeting and perpetuating fear-mongering headlines that simply do not tell the whole story. And as for this one, I think I’ll keep that side bacon, thank you very much.

This article was published in The Ryersonian on Nov. 4, 2015.

 

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