The World Health Organization (WHO) International Agency for Research on Cancer (IARC) has classified processed meat as carcinogenic to humans, which is the most dangerous rating that any substance can receive from the IARC. Red meat on the other hand is considered probably carcinogenic to humans. Shockingly, the Global Burden of Disease Project estimates that cancer induced by processed meat causes 34,000 deaths per year while cancer induced by red meat causes 50,000 deaths per year. Equivalently, that is nearly 10 deaths every hour due to cancer caused by processed meat and red meat.

According to scientific studies, most cases of meat induced cancer are colorectal, but meat can also cause cancer in the prostate, pancreas, esophogaus, and stomach. Also, the risk of cancer is found to increase with the amount of meat consumed, with every 50 gram portion per day of processed meat consumed increasing the risk of colorectal cancer by 18%, and every 100 gram per day portion of red meat consumed increasing the risk of colorectal cancer by 17%.

Red meat naturally contains heme iron, which is carcinogenic since it causes oxidative stress and DNA damage, and heme iron catalyzes the formation of N-nitroso compounds, which are potent carcinogens. According to a study, the N-nitroso compounds which arise from ingesting red meat include diazopeptides and N-nitrosopeptides, which form DNA adducts in the colon, leading to mutations and potentially cancer. .

Other carcinogenic compounds arise when red meat is cooked, such as heterocyclic aromatic amines and polycyclic aromatic hydrocarbons. Apparently, high temperature cooking via pan-frying, grilling, or barbecuing increases the concentration of these carcinogens in the meat. Therefore, it is perhaps best to cook meat slowly on a low temperature.

Processed meat, which is meat that has been salted, fermented, cured, or smoked in order to preserve the meat or enhance its flavor, contains even more carcinogens than cooked red meat. Specifically nitrates are added to processed meat and then these turn into nitrites within the body, which can then further react with amino acids to form carcinogenic nitrosamines.

All of this being said, even the WHO IARC is not recommending that people simply stop eating meat, since meat consumption has important dietary benefits. However, this research shows that if someone is consuming meat then they should seek out red meat and avoid processed meat. Further, the red meat should be cooked on a low temperature, and certainly the red meat should not be burned. Finally, red meat should only be eaten as a treat once in awhile rather than constantly consumed.