*The Function of Ascorbic Acid through Occam's Razor: What We Know, What We Presume… DOI: http://dx.doi.org/10.5772/intechopen.109434*

The common opinion that antioxidants are the key to a long and healthy life dates back to the 1970s and 1980s, when Linus Pauling (who had been awarded the Nobel Prize twice, in Chemistry and for Peace) became a fervent communicator of this new concept [53]. The main assumption of his theory was that high AsA doses (18 g daily or more!) can counteract many diseases (from the common cold to cancer) and delay aging. Pauling's conclusions were mainly based on his own experience and on the limited clinical evidence obtained by Ewan Cameron, a physician who had been using AsA in the treatment of cancer with apparently good results. Pauling's claims opened the way to the view that antioxidant supplements are always good for human health irrespective of the amount taken: the more the better. It is worth noting that the main international agencies suggest a daily intake of vitamin C in the order of 80–90 mg per day [54].

Of course, it is undeniable that AsA, with a redox potential of 0.28 V [55], is an excellent reducing agent and an efficient antioxidant. As already mentioned, the fortunate encounter of Szent-Györgyi with his hexuronic acid occurred because it inhibited the peroxidase reaction [1]: a typical "antioxidant job". On the other hand, the opinion that harmful ROS must be totally removed is not consistent with many experimental observations, which could be summarized in three categories. First, enzymes "deliberately" producing ROS are known for a long time: NADPH oxidases occur in many organisms and use NADPH-reducing power to produce ROS. Second, ROS in turn activate several forms of communication, including defense response and epigenetic control of lifespan extension [56–59]. Third, as a corollary to the previous point, some reports established that improving ROS removal beyond a certain threshold has negative effects on the lifespan of different organisms [60]. In addition, recent studies on AsA reactivity showed that it reacts preferentially with iron and copper, rather than ROS [61, 62]. All this concurred with the definition of a totally new vision of ROS/antioxidant dynamics, overriding the simplistic "good antioxidant/bad ROS" duality [63–67]. Aerobic organisms produce ROS, but rather than finding ways to erase them, cell metabolism implemented new resources in two different directions: on one side developing antioxidants to control ROS accumulation in some specific cell locations or developmental stages; on the other side using ROS generated by fluctuating environmental conditions as an opportunity to drive cell responses.
