Processed meats have been classified as carcinogenic to humans, and red meat has been classified as probably carcinogenic to humans, according to a new report from The World Health Organization’s International Agency for Research on Cancer (IARC) Monograph Working Group published in The Lancet.
The Working Group determined that processed meats cause colorectal cancer in humans and have a positive association with stomach cancer. They also found that red meat has a positive association with colorectal, pancreatic, and prostate cancers.
Red meat includes any unprocessed meat from a mammal, including minced or frozen meat. Processed meats include any meat that has been salted, cured, fermented, smoked, or put through any other process to help preserve the meat or enhance its flavor.
The IARC Monograph Working Group consists of 22 scientists from 10 countries. They assessed over 800 epidemiological studies that investigated an association between red or processed meat and any type of cancer. The studies included data from diverse ethnicities and diets.
The studies yielded a significant body of evidence on meat consumption and colorectal cancer. Out of 18 cohort studies that provided relevant data, 12 showed a positive association between consumption of processed meat and colorectal cancer. Out of 14 cohort studies that provided relevant data, 7 showed a positive association between consumption of red meat and colorectal cancer. The Working Group gathered supporting evidence both case-control studies and a meta-analysis of cohort studies.
Aside from colorectal cancer, the studies included data on 15 other types of cancer. Analysis of these data showed a positive association between red meat consumption and cancers of the prostate and pancreas. The researchers also found a positive association between consumption of processed meats and stomach cancer.
The Working Group notes that meat processing can cause the formation of carcinogenic chemicals such as N-nitroso-compounds (NOC) and polycyclic aromatic hydrocarbons (PAH). Certain cooking methods, especially those that use high temperatures, may also produce known and suspected carcinogens.