Bacon (photo via Flickr/Kietil Ree).

‘The World Health Organization (WHO) announced on Monday that it has classified processed meat as a human carcinogen.

‘Red meat also was classified as a probable human carcinogen, according to the release by WHO’s International Agency for Research on Cancer (IARC).

‘The group cited “sufficient evidence” linking processed meat—such as bacon and sausage—to colorectal cancer, and noted associations with stomach, prostate, and pancreatic cancers. Processed meat is preserved by smoking, salting, fermenting, or by the addition of chemicals, and the category includes bacon, sausage, deli meats, and hot dogs. The red meat category includes beef, veal, pork, and lamb. . . .

‘Like much of the research on how diet affects health, the research on the link between meat and cancer has enough ambiguity that it’s possible to cherry-pick a research list that supports either position, but many reviews of research on the best-established link between meat and cancer—colorectal cancer—find, as this 2014 review published in the American Journal of Clinical Nutrition does, that there is a convincing association between meat eating and colorectal cancer. The question, though, is whether the meat eating causes the cancer, or whether meat eaters, who are different from non-meat eaters in many ways, are eating or doing other things that put them at risk. . . .

The IARC acknowledges the difficulty of determining causality, but their report concludes that, ‘the consistent associations of colorectal cancer with consumption of processed meat across studies in different populations, which make chance, bias, and confounding unlikely as explanations.’

On red meat, though, ‘Chance, bias, and confounding could not be ruled out with the same degree of confidence.’. . .