In the past couple days, unless you’ve been living under a rock, you’ve probably been seeing headlines of the “Red Meat as Carcinogenic as Smoking!” variety. To understand this issue, you have to understand just a bit about the science of red meat metabolites as well as about epidemiology. The following is a quick primer.
What did the paper actually say? The headlines are based on a short summary paper that refers to a massive analysis of over 800 studies. Earlier this month, experienced researchers met at the International Agency for Research on Cancer (IARC), an arm of the World Health Organization (WHO), and came up with some strong conclusions on red meat. Specifically, with regard to colorectal cancer, they classified processed red meat as a “Group 1” carcinogen (“carcinogenic to humans”). As for regular red meat, it was classified as a “Group 2A” carcinogen (“probably carcinogenic to humans”).
First, the findings were mostly referring to colorectal cancer (the third leading cause of cancer death in the US), so you can’t generalize the researchers’ findings to all other cancer types. Second, it’s not like we didn’t know this stuff already. Processed red meat has been strongly linked to colorectal cancer for many years. Regular unprocessed red meat is more of a mixed bag in terms of evidence, but still has several mechanisms by which it may increase cancer incidence. Third, just because the WHO is a big deal doesn’t mean they can’t be wrong. Expert opinion doesn’t equal fact. Major health organizations have disagreed on the health impact of food and nutrients several times before. Fourth, much of the evidence that was reviewed was epidemiological evidence, observing people over time to see if disease develops. Much of the evidence reviewed was observational/epidemiological in nature, rather than from randomized trials. Finally, and we can’t say this enough: The dose makes the poison.This means that causation is hard to pin down. Red meat is not inherently unhealthy. As with most everything, the type and dose make the poison. There is always something to be said about moderation.