ABSTRACT
Ageing is characterized by many changes in the organism and very complex difficult process to understand. Although this process is tried to be explained with various theories, these approaches should not be considered separately from each other. The free radical theory put forward by Harman in 1956 and later the arrangement of this theory centered on the mitochondria were accepted. Antioxidant defense systems have been shown to work in balance with reactive oxygen products against the damage caused by reactive oxygen products at pathological levels. It has been shown that oxidative stress arises as a result of the disturbance of this balance. It has been shown that various diseases other than aging due to oxidative stress occur. It has been reported that reactive oxygen products formed in physiological doses can protect the organism against various diseases. Today, oxidative damage in the organism can be measured at certain levels and this damage mechanism can be shown in some diseases.