ELi5: why are processed meats Group 1 carcinogenic along cigarettes and plutonium?


ELi5: why are processed meats Group 1 carcinogenic along cigarettes and plutonium?

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Being a Group 1 carcinogen means that there is a strong evidence of a link between the material/habbit/consumption and the chance on getting cancer.

In Australia, one in six new bowel cancer cases in Australia were associated with consuming too much red meat and processed meat. In terms of cancer risk there is no reason to cut red meat completely from your diet, but by limiting the amount you eat, you can reduce your risk of cancer.

Processed meat is often made from red meat and it also contains added nitrates and nitrites which are also broken-down during digestion to form chemicals that can cause cancer. Another factor could be that those who eat a lot of meat may miss out on eating other protective foods such as fruit and vegetables or wholegrain cereals.

The simple answer is that “Group 1” was not defined well. It just means we “know for sure” that something causes cancer.

But think about what this implies. Suppose we “know for sure” that product A will cause cancer in 99% of the people who use it. That’s Group 1! Clearly we should disallow that product.

Suppose we “know for sure” that product B will cause cancer in one person out of a million who use it. Since we “know for sure,” that’s also Group 1, but it’s barely dangerous at all. No reason to ban that product.

I’ve used exaggerated numbers to make the point, but the big picture is that cigarettes are super-dangerous whereas processed meats are not nearly so much.

Processed meats contain a class of compounds called nitrites that are toxic to bacteria. This prevents the meat from spoiling and prolongs its life. However, nitrites can equilibrate with nitrous acid in the body. The DNA bases cytosine and adenine can become oxidatively deaminated into uracil and hypoxanthine from the action of nitrous acid. In other words, nitrous acid can mutate your DNA by changing the bases in the DNA itself. Over time, when enough mutations in certain genes accumulate in a cell, it can become cancerous.

Basically we know with enough certainty that processed meats cause cancer. Just as much as we know plutonium exposure or smoking causes cancer. Group 1 just means “we are very very sure about this guys”.

The thing that is probably confusing you here is the classes:

They say HOW SURE we are that something causes cancers, not HOW SEVERE the cancerios effect is.

This just says that we are 100% sure it has a carcinogenic effect. Something in class 2 can be way more dangerous, but we are not completly sure about it yet (=more research required). What it doesn’t say is HOW bad it is.

So no, processed meat is not as bad as plutonium. Its not healthy, but you are probably fine with a reasonable amout of processed meat.