Processed foods are unhealthy when they contain high levels of saturated fats or trans fats or additives such as sodium, sugar, nitrites and nitrates; or when they are overprocessed so they lose their nutrients. However, some processed foods are beneficial, including minimally processed foods that retain their nutrients, such as quick frozen vegetables; pasteurized foods that no longer contain harmful bacteria, such as milk; or certain foods that are cooked to enhance their nutritional value, such as tomatoes.
Saturated and trans fats are associated with several health risks such as obesity, cardiovascular diseases and cancer. Trans fats are fats that are artificially produced when vegetable oils are hydrogenated to make them solid at room temperature. They are commonly found in margarine, snack and junk foods, packaged baked goods, and fried fast foods. Excessive levels of sodium increase the risk for cardiovascular diseases, and high intake of sugar contributes to obesity and endangers diabetics. Because nitrate and nitrite preservatives may be carcinogenic, the World Health Organization and U.S. Food and Drug Administration set upper limits for them in food.
Some unhealthy processed foods to avoid include canned foods containing high amounts of sodium or fat, high-calorie junk foods such as candies and chips, boxed cakes and cookies, sugary breakfast cereals, and processed meats and hams. Other foods to pass are fish sticks encased in high-sodium batter, frozen dinners laden with fat and sodium, as well as packaged meals prepared with refined white flour instead of whole grains. Overprocessed foods also lose a lot of their natural vitamins and minerals during the industrial cooking process and therefore have low nutritional value.