In 2019, I was surprised to learn that Processed Meat was classified as IARC Group 1 Carcinogen in 2015. What does that mean? What is IARC? What does it mean to classify something as Group 1 Carcinogen?

What is "Processed Meat"? Wikipedia article on Processed Foods explains:

I noticed that definition of Processed Meat is very broad!

How harmful is Processed Meat? In 2015, Processed Meat was classified as IARC Group 1 Carcinogen!

IARC (International Agency on Research in Cancer) is part of WHO (World Health Organization); it focuses on cancer research. It divides carcinogens (substances capable of causing cancer in living tissues) into 5 broad groups (see image below).

How are IARC Groups defined? See this article: A Rough Guide to the IARC's Carcinogen Classifications (2015)

Group 1 consists of carcinogens for which "sufficient evidence in humans; causal relationship established'.

Those familiar with Machine Learning or Statistical Modeling techniques in life sciences and medicines may appreciate how much effort it takes for something to be classified as a "causal" agent for some phenomenon, and agreed upon by a committee of world scientists. For Processed Meat, causality has been established; in 2015, it was agreed upon that it causes cancer in humans. That's why it's classified as IARC Group 1 Carcinogen.

Complete list of IARC Group 1 Carcinogens? here (Wikipedia). This list includes carcinogens like asbestos, plutonium and alcoholic beverages. Yes, alcohol is also known to be a Group 1 Carcinogen! Many of my friends don't seem to know this.

Is processed meat carcinogenic?

• IARC: Carcinogenicity of consumption of red and processed meat by Bouvard et al, The Lancet Oncology, 2015, 16 (16), pp.1599-1600 (PDF)

  This article defines processed meat as follows:

  "Processed meat refers to meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance fl avour or improve preservation. Most processed meats contain pork or beef, but might also contain other red meats, poultry, off al (eg, liver), or meat byproducts such as blood."

  Summary of concerns:

  "Meat processing, such as curing and smoking, can result in formation of carcinogenic chemicals, including N-nitroso-compounds (NOC) and polycyclic aromatic hydrocarbons (PAH). Cooking improves the digestibility and palatability of meat, but can also produce known or suspected carcinogens, including heterocyclic aromatic amines (HAA) and PAH. High-temperature cooking by panfrying, grilling, or barbecuing generally produces the highest amounts of these chemicals."

  Is home cooked meat okay? The excerpt above is fascinating. It explains that even home cooked meat may produce HAA and PAH, which are known or suspected carcinogens. And high-temperature cooking by panfrying, grilling and barbecueing produces the highest amounts of such chemicals. How may we minimize cooked meat carcinogens? Dr Greger explores the subject in this article: Avoiding Cooked Meat Carcinogens (2013). For more details on HAA, PAH and other potentially health damaging compounds produced when we cook meat, see Is Meat An IARC Group 1 Carcinogen?

  No wonder point 4(d) in American Heart Association (AHA)'s 2021 nutrition guidelines says "if meat or poultry is desired, choose lean cuts and avoid processed forms" — the key word is "if" — my interpretation is that AHA is telling us that meat and poultry are optional; if we really wish to consume then, then we should choose lean cuts (to reduce animal fat) and to avoid processed meat (because it's an IARC Group 1 carcinogen).

• WHO: Q&A for Cancer: Carcinogenicity of the consumption of red meat and processed meat (2015)

US Dietary Guidelines and Processed Meat: In 2020, Dr Greger gave a 3-min presentation imploring the US Dietary Guidelines Advisory Committee for 2020 to start clarifying that Processed Meat is harmful and should be avoided, based on the IARC Group 1 Classification of Processed Meat.

News:

1. (2019) New York City Schools Ban Processed Meat.
2. (2019) 69% of London Parents want Processed Meat Banned from Schools
3. (2021) Judge Rules That California Must Answer Lawsuit Calling for Processed Meat to Be Added to State Carcinogen List.

   In California, when a commercially sold product contains something listed in Proposition 65, manufacturers must label it with "WARNING: This product contains chemicals known to the State of California to cause cancer and birth defects or other reproductive harm."

   Should processed meat be part of Proposition 65? The State of California will decide soon. In 2015, processed meat was classified as an IARC Group 1 carcinogen by WHO. This group includes hundreds of substances known to cause cancer, e.g., tobacco, lead, asbestos, radiation & alcohol.

I was wondering… It's been 5 years since Processed Meat was classified as IARC Group 1 Carcinogen. How many more years will it take before it becomes common knowledge and we have guidelines or regulations in place to help us avoid Processed Meat consumption?