In an article published today in The Lancet, the World Health Organization concludes there is sufficient evidence that eating processed meats such as bacon, sausages and hot dogs can cause cancer. Additionally, the WHO says there is some, but much more limited evidence, that eating red meats can cause cancer.
This conclusion comes from a group of 22 scientists who met on behalf of the International Agency for Research on Cancer, an agency within the WHO that evaluates potential environmental causes of cancer and categorizes their hazard based on strength of scientific evidence.
The results of their evidence review place processed meats in the same category of cancer hazard as tobacco and asbestos. Red meats including beef, pork, veal and lamb were placed in a lesser category, which indicates the IARC deems they are “probably carcinogenic” to people.
It is important to note that this does not mean that tobacco and asbestos are equally dangerous as processed meat consumption. While they are in the same category of cancer hazard, the classification describes only the strength of scientific evidence that something is capable of causing cancer. It is not an assessment of risk.
In response to the classification, Susan Gapstur of the American Cancer Society told NPR that the society recommends “consuming a healthy diet with an emphasis on plant foods and limiting consumption of processed meat and red meat.”
The American Cancer Society recommendation is supported by research. Both the ACS—and The Lancet article published today—reference a systematic literature review on colorectal cancer published in 2011 by the World Cancer Research Fund, which found a 16 percent increased risk of colorectal cancer associated with each 100 grams of red and processed meat consumed per day. This is an amount of meat the size of a deck of cards.
The WHO classification of red meat does not consider potential benefits research has shown eating red meat can have. In their review, the WHO does acknowledge red meat contains “high biological-value proteins and important micronutrients such as B vitamins, iron and zinc.”
The North American Meat Institute, for its part, released a statement defending potential benefits of red meat consumption.
“Scientific evidence shows cancer is a complex disease not caused by single foods and that a balanced diet and healthy lifestyle choices are essential to good health,” writes Barry Carpenter, president of the North American Meat Institute, in a statement on the new WHO classification.
Carpenter emphasizes the limited scope of assessing cancer hazard. “IARC’s panel was given the basic task of looking at hazards that meat could pose at some level, under circumstance, but was not asked to consider any off-setting benefits, like the nutrition that meat delivers or the implications of drastically reducing or removing meat from the diet altogether.”