The science: IARC assessed more than 800 epidemiological (population based) studies to evaluate the link between red meat, processed meat, and cancer, giving the greatest weight to prospective cohort studies, and taking additional evidence from high quality population based case-control studies. They made a point of focusing on data that included large sample sizes and controlled for possible confounding factors (these are other factors that could be responsible for the same result, for example smoking). Their meta-analysis found:
1. An 18% increased risk of colon cancer per 50g of daily processed meat consumption (with confidence that there was no confounding or other explanation for the results);
2. A 17% increased risk of colon cancer per 100g of daily red meat consumption (with less confidence that there was no other explanation for the results)
3. Positive associations between consumption of processed meat and stomach cancer;
4. Positive associations between consumption of red meat and cancers of the pancreas and prostate.
Based on these results, they have classified processed meats as being carcinogenic (cancer causing), and red meat as ‘probably carcinogenic’ to humans.
It seems that how meat is cooked or processed is relevant to this discussion. Meat processing, such as curing or smoking, can result in the formation of cancer causing chemicals such as N-nitroso-compounds and polycyclic aromatic hydrocarbons (PAH). Cooking meat can produce chemicals also suspected of causing cancer, including heterocyclic aromatic amines and PAH. High temperature cooking (pan frying, BBQ, or grilling) produces the highest amounts of these chemicals.
While red meat does contain lots of good quality protein and important nutrients such as B vitamins, iron and zinc, these nutrients can be found in other, healthier food choices.
So, meat lovers: you’re best off to limit your intake of processed meats and red meats; consider healthier alternative such as poultry or fish.
A scientific discussion of the evidence can be found in The Lancet Oncology, and you can read more about the IARC (if interested) here.