A preservative is any ingredient added to a food to slow down spoilage. Antioxidants are an important branch of preservatives as they inhibit the oxidisation process which turns fats rancid. Both preservatives and antioxidants can come from natural sources (such as vitamin E and rosemary oil) or be artificially created. Here we will talk only about artificial preservatives and antioxidants.
Although artificial preservatives certainly work at slowing down decomposition, there are wide ranging concerns over their effects on health. Ethoxyquin (E324), for example, has been linked to the development of allergic reactions, skin disease, behaviour problems and far worse conditions. Likewise, the antioxidants BHA (E320) and BHT (E321) have long been suspected of contributing to cancer. Another common preservative, potassium sorbate (E202), is listed as a skin, eye and respiratory irritant.
Needless to say, while there is any uncertainty over their side effects, these ingredients are certainly best avoided.
If a food contains artificial preservatives or antioxidants it must be stated somewhere on the label. They may be listed in a number of ways and are not always easy to spot: ‘preservatives’; ‘EU permitted additives’; ‘BHA and BHT’; and ‘E320 and E321’ are all ways of listing the same preservatives. They may also not appear on the ingredients list at all but be found at the end of the typical analysis. If you want to be completely sure, look for foods that clearly state ‘no artificial preservatives’.