Nitrites and nitrates present in processed meats undergo chemical transformation into nitrosamines, such as NDMA, under acidic gastric conditions, and these nitrosamines are carcinogenic agents that cause DNA damage.

Study: Risk of colorectal and other gastro‐intestinal cancers after exposure to nitrate, nitrite and N‐nitroso compounds: a follow‐up study

The study looked at people eating foods with nitrites and nitrates, like cured meats, and found it increased cancer risk, which matches the claim that these can form harmful chemicals in the stomach.

Study: Endogenous Formation of N-Nitrosodimethylamine (NDMA) from Dietary Nitrite and Nitrate Intake and Its Association with Cancer Risk.

The study found that eating foods with nitrites and nitrates, like processed meats, can lead to harmful chemicals that raise cancer risk, which backs up the claim.

Study: Dietary Nitrosamines from Processed Meat Intake as Drivers of the Fecal Excretion of Nitrosocompounds

The study shows that eating processed meats leads to more harmful chemicals in the gut that can damage cells, which supports the idea that these meats might cause cancer.

Study: N-Nitrosamines: A Potential Hazard in Processed Meat Products.

The study says that nitrites and nitrates in processed meats can turn into harmful chemicals in your stomach that might cause cancer, which matches the claim exactly.