So how can we explain the protective capacity of H2O2 when this radical is well known to be toxic, killing cells? According to the first author of the article, Ana Mesquita, and Ludovico the explanation is in a phenomenon called hormesis, where a substance normally toxic can have beneficial effects if used in low doses. Why this happens is not totally clear but it is suspected that small amounts of stress (like small amounts of H2O2) can activate the body's repair mechanisms without really provoking any damage so ending up having "bizarre" beneficial effects. In this case H2O2 is enough to activate the antioxidants specific for O2- , slowing down the aging normally provoked by this radical.

In conclusion, Ludovico and colleagues' new work have a few crucial results - first that it is possible to have little oxidative damage despite having high levels of free radicals (H2O2 in yeast with a low caloric diet) and second, that high levels of oxidative damage can exist in long-living organisms (like it occurs in yeast without functional catalases). Finally, in discovery that puts up side down the way we see anti-aging therapy and research, they prove that a free radical (H2O2) can actually be anti-aging.

 These results seriously challenge the free radical theory and introduce a totally new vision for the role of free radicals (at least H2O2) in the body,  and no doubt will have important implications in the way aging processes are seen from now. After all, the free radical theory has guided investigations into the causes and consequences of aging for more than 50 years, while free radicals have been always considered the "bad guys". And while (most) radicals  probably have a role in the deterioration that accompanies old age, the process (and the radicals' role) is no doubt much more complex than the simple equation - free radicals: oxidative damage: aging - that the free radical theory proposes. 

 Interestingly, Ludovico's results also suggest that H2O2 can be used as an anti-inflammatory since O2- is known to participate in inflammation although this will need further research.  Another interesting discovery is the fact that catalases appear as pro-aging in opposition to the current idea - behind much research - that these proteins can be used to slow down aging.

Finally this new work might also explain why, contrary to what is expected by the radical theory, in some studies, anti-oxidants are shown to reduce longevity.

But would this affect the anti-oxidant industry? Most probably not.  After all there was never any scientific evidence that dietary anti-oxidant supplements affected the body's free radicals levels (despite what the industry want us to believe), and, still, millions of people continue to buy this elusive promise of a new lease of life. In the end, it's all about hope (at least for now)

Source :  University of Minho