Fats breakdown into smaller odorous molecules in the presence of oxygen. This mean that the product is spoiled and that it shouldn't be eaten any more. Unsaturated fat become easily oxidized. Some antioxidants are used in order to stop this process and keep the food fresh for a longer time. BHT (butylated hydroxytoluene) and BHA (butylated hydroxyanisole) are among the antioxydants that are added to cereals to keep them fresh and extend their shelf life. Studies on these antioxidants are inconclusive, some suggest that they cause cancer whereas other say that they prevent the disease. These additives are used at very low concentrations and in theory do not pose any health risks at that concentration.

             Sulfites are the only food additives that have been linked with human death. Sulfites are responsible for keeping fruits and vegetables looking fresh. They prevent a "browning" reaction that makes the fruit look brown. They were widely used in salad bars but now are outlawed because people who were very sensitive to this chemical died. An elderly woman died after eating raisin bread in which sulfites were used to keep the raisins fresh. Proper labelling is now required even for secondary ingredients, such as the raisins in the case of the raisin bread.

             Nitrites are used in food to avoid botulism poisonning. Nitric oxide is the active ingredient in nitrites, which have been linked to deaths if consummed in high doses. Animals who were fed fish preserved with nitrites got liver cancer. This problem was traced to nitrosamines, a cancer causing agent that is created by a reactin between amines and nitrites. This reaction could be reduced by the presence of vitamines C and E. Lately the level of nitrites in our food has been less than 100 parts per million. Nitrosamines have been demonstarted to be naturally created in our bodies without any connnection to the nitrites that we consume as food additives.