Why do red meat and processed meat cause cancer?
Both red meat and processed meat contain a variety of chemicals harmful to human health. For example, bacon, barbecue and fried meat contain polycyclic aromatic hydrocarbons (PAHs), while meat heated at high temperature contains heterocyclic amines (HAA), which is genotoxic. These chemicals can cause DNA damage, but at present people lack direct evidence of DNA damage after eating meat.
After eating red meat or processed meat, human colon will metabolize and produce nitroso compounds (NOC), which will react with DNA to produce adducts, leading to DNA malformation. The researchers detected this reaction product by rectal biopsy of people who ate 300-420 grams of red meat every day.
In addition, the researchers used rodents such as mice to find that the intake of red meat and processed meat would lead to the increase of lipid peroxide products in their feces. Three independent experiments have proved that the changes of oxidative stress indexes in urine, feces and blood are related to the intake of red meat or processed meat. After eating red meat, the number of bacterial mutations in human urine increased. In 185 colon cancer samples, the researchers found that 75 cases (43%) had APC gene mutation, and 4 cases (23%) had gene promoter DNA methylation level change.