A December 2001 study (1) found that, 

“Atherosclerosis may result partly from processes that occur following food consumption and that involve oxidized lipids …” 

“We suggest that human gastric fluid may be an excellent medium for enhancing the oxidation of lipids and other dietary constituents.” 

“The results indicate the potentially harmful effects of oxidized fats intake in … catalysts found in foods, and the major benefit of including in the meal plant dietary antioxidants.”

A November 1986 study (2) said,

“All foods that contain lipids are susceptible to oxidation but especially affected are foods which are dehydrated, subjected to high temperatures or cooked and subsequently stored, e.g. dehydrated eggs, cheeses and meats, foods fried in frying oils, and cooked (uncured) meats.”


References

(1) “The stomach as a bioreactor: dietary lipid peroxidation in the gastric fluid and the effects of plant-derived antioxidants”

(2) Occurrence of lipid oxidation products in foods