There are natural antioxidants, such as enzymes, vitamins and minerals, within the cat's body. These are designed to protect the body from damage caused by substances called free radicals that are produced during day-to day metabolism. Unless 'mopped up' by the body free radicals can damage cells. As a cat gets older it may get less efficient at mopping up free radicals and this has been implicated as a factor in the ageing process. It has been suggested that providing more natural antioxidants in the food may keep a cat healthier for a longer time.

Some antioxidants that are present in dry food have been added to extend the shelf life of the food. Canned foods are preserved by heat sterilisation and sealing and do not require the addition of antioxidants.