A 2005 study suggests to us a conclusion that food that which contains iron which is then cooked in vegetable oil could cause inflammation in the digestion system and that adding Vitamin C and/or stress may not help.

Source

Lipid Peroxidation by “Free” Iron Ions and Myoglobin as Affected by Dietary Antioxidants in Simulated Gastric Fluids Agric. Food Chem. 2005, 53, 9, 3383–3390