Not many subjects in the field of life sciences have led to so many discussions as antioxidants. Polarised views on antioxidants range from antioxidants cure any disease to antioxidants increase mortality. Other opposing views are the more the better versus at high doses, antioxidants become pro-oxidant. In a recent review (Bast and Haenen, 2013), we have addressed 10 misconceptions about antioxidants and analysed this antioxidant controversy. An important factor is that the word antioxidant designates a general common action which does not take into consideration that antioxidants are in fact distinct chemical entities with different modes of action for their specific effects.
Antioxidants should be clearly defined based on their physiological and physico-chemical properties. With this in mind, let us categorise and start by asking the question, what is an antioxidant? We will answer this by looking at nutritional antioxidants (i) from a perspective of direct scavengers of reactive oxygen species (ROS); (ii) with regard to their effect on ROS formation; and (iii) their interplay with other enzymatic and non-enzymatic antioxidants.
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