The World Health Organization (WHO) report linking red and processed meat consumption to colon cancer stirred controversy as soon as it was published on October 26. In particular, the North American Meat Institute (NAMI) called the WHO’s claims “alarmist” and “dramatic.” But now it’s time to take a step back and look at the data on the competing claims made by the WHO and the meat industry.
Using data from the Department of Agriculture and National Cancer Institute, HealthGrove looked at the relationship between red meat consumption and colon cancer. Do red and processed meats really cause cancer? It turns out the answer isn’t as simple as either the WHO or the NAMI would have you believe.
Instead, much of the misunderstanding comes from how the meat is categorized. The International Agency for Research on Cancer (IARC) — the WHO agency that released the report — provided technical definitions for the two, but in the media frenzy that followed the release of the report, they were often confused. Basically, red meat can be processed, and processed meat can be red, but they’re not always the same. For example, both bacon and a cut of steak from the butcher are red, but bacon is processed while steak isn’t.
In their formal response, the North American Meat Institute, the largest trade association for the meat industry, stated that there is “no correlation between meat and cancer.” In doing so, they lumped red and processed meat together and likely misled many readers into doing the same. Even the papers cited by the NAMI are clear about this distinction, though the NAMI is not.
The IARC ranks substances for carcinogenicity based on real-world observations and lab tests. Their five categories for carcinogenicity, from most cancerous to least, are Group 1, 2A, 2B, 3, and 4. In their report, the IARC classified processed meat as carcinogenic to humans (Group 1), based on sufficient evidence that consumption causes colorectal cancer in humans. However, red meat fell into Group 2A: probably carcinogenic to humans, based on limited human evidence and strong biological evidence.
The carcinogenicity of processed meat goes mostly unchallenged, according to data cited by both the IARC and the meat institute. Even though the meat institute claims there is no correlation between processed meat and cancer, they contradict themselves with the scientific evidence they cite — both articles mention an association between processed meat and cancer.
When it comes to red meat and cancer, though, things aren’t as clear. To examine this relationship, HealthGrove looked at red meat consumption and colon cancer mortality over time. The trends support the IARC’s categorization.
Since peaking around 1970, American’s consumption of red meat has experienced a consistent decline.
When looking at the mortality of colon cancer over time as shown below, one can see a similar downward trend. These visualizations support the idea of a correlation between the two. However, this does not mean one caused the other.
With these kinds of epidemiological studies, it’s important to keep in mind the differences between causation and correlation. And there very well may be confounding variables. Sure, the mortality of colon cancer could have gone down due to decreased red meat consumption. But it could also be due to advancements in colon cancer treatments. Or increased consumption of vegetables. Or anything else.
Although lab studies indicate that there might be something in red meat that could cause cancer, the IARC explains that, in the grand scheme of things, there isn’t yet a lot of evidence for this cancer-causing relationship.
It is this weak, and therefore inconclusive, association that landed red meat in Group 2A as opposed to Group 1. So, despite seemingly being at odds, the IARC and meat institute actually cite data supporting roughly the same conclusions.
They also agree on other points. Both confirm that red meat has nutritional benefits. The IARC attested to red meat’s nutritional value in its report (though the meat association claimed it ignored that fact). And, both organizations corroborate that cancer is a complex disease not caused by any one single factor. The meat association does so in its formal response, and the IARC does so on its website.
The biggest takeaway from both organizations is something we’ve all heard before: moderation. Red and processed meats have nutritional benefits and are fine in limited quantities as part of a balanced diet. Just don’t go living off hot dogs and bacon.
This article was written by Sabrina Perry from Business2Community and was legally licensed through the NewsCred publisher network.