Oxidative stress, the term and the concept.

The 30th birthday of a central concept in biomedicine, such as oxidative stress (OS) is a good time for re-evaluation of its contribution to science and particularly to the field of redox biology. In his recent communication, Sies described the history of the concept as well as the benefits and pitfalls of the term OS. In this mini-review, we discuss the problems associated with the still common perception of "bad OS, good antioxidants". Specifically, the term OS is an intuitively understood term originally used to describe an imbalance between pro-oxidative factors and anti-oxidative factors. It has no units, its level is dependent on the way it is measured and there is no correlation between various criteria of OS, which indicates that there are sub-classes (types) of OS (other than the classifications presented by Sies). In spite of these limitations, it is commonly regarded a measure of a person's probability to suffer from oxidative damages and is being held responsible for many diseases and antioxidants are predicted to be good to us. In fact, a "Basal OS" is vital and antioxidants may interfere with the mechanisms responsible for maintaining the oxidative status. We also discuss the linkage of OS to the outcome of antioxidant supplementation and comment on the importance of kinetic studies in evaluation of OS and on the ranking of antioxidants.