Category: Facebook

I’m all for looking for deeper context. Dietary headlines are pretty much always overly simplistic, and it’s important to consider scale (doubling a tiny risk is still tiny), interactions, and trade-offs (avoiding one ingredient and increasing another beyond healthy levels isn’t going to help).

But ridiculing an organization for saying that sunlight and air pollution can cause cancer? That’s so blatantly dishonest I thought I was reading a satirical quote from the Onion.

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Also: Treating the various categories as if they’re all the same. Quick reference: Group 1 means there’s sufficient evidence that something causes cancer. Group 2A and 2B mean there’s limited evidence, so they’re not saying they’re sure. Group 3 means that there’s no indication that it causes cancer, but they haven’t ruled it out.

If anybody tells you something is dangerous because it’s a Group 3 carcinogen, they are either mistaken or lying to you. It might very well be dangerous for other reasons, but Group 3 specifically means they looked at it and didn’t see enough evidence either way.

(I recently saw someone claiming bananas were carcinogenic because of the ethylene gas used to ripen them after they’ve been picked. Ethylene is in Group 3. It’s also given off naturally by plants to do things like…ripen fruit.)

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https://www.iarc.fr/wp-content/uploads/2018/07/pr240_E.pdf

Here’s the actual IARC press release. It still doesn’t describe the scale of the effect they found, but it does at least define what they consider to be “processed meat” (basically anything cured, smoked, etc. so I guess that does include cold cuts). It’s worth noting that they don’t suggest people *stop* eating red & processed meat, but *limit* it, and that that risk/benefit analysis needs to be done to determine the best guidelines.

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https://www.vox.com/2015/10/26/9617928/iarc-cancer-risk-carcinogenic

Aha! Some numbers to indicate the actual *scale* of the risks involved: “In the United States, a person’s lifetime risk of getting colorectal cancer is roughly 5 percent. The IARC says that eating 50 grams of processed meat per day (about one hot dog’s worth) will boost that to about 6 percent.” For comparison, the article cites the lifetime risk of lung cancer at 1.3% for non-smokers and 17.2% for regular smokers – a *much* bigger difference!

I’d seen the 18% increase stat in several articles, but this is the first place I’d found the baseline rate, which is an important piece of information.

It’s an 18% increase for each daily serving, basically. If you assume the average American eats say, three servings of red/processed meat a day (I don’t know) for that 5% risk, then eating four servings daily brings you to 6%, five daily servings would bring you up to 7% and so on. Presumably going veggie or sticking to poultry would drop it to 3%. And that’s not considering confounding factors.

I understand reporting the findings primarily in terms of ratios since different cultures eat different amounts on average and will have different average rates…but at the same time, if you’re in science you’ve got to know that science reporting — and worse, health reporting — is pretty much worthless at trying to find the context. A few countries’ average consumption and cancer rates should have been in the press release.