A group of researchers at Nippon Medical School in Japan published in prestigious medical journal, Nature Medicine, in 2007 that molecular hydrogen might act as a selective antioxidant (1). Specifically, the study suggested that molecular hydrogen might neutralize hydroxyl radical, the most reactive of all reactive oxygen species (ROS), as well as peroxynitrite, the most reactive of all reactive nitrogen species (RNS).

You can find a variety of antioxidant supplements on the shelves of pharmacies and health stores. However, there are certain misconceptions among the public in relation to the role of oxidants and antioxidants in maintaining health.

Oxidants and Antioxidants

Oxidants (ROS and RNS) contain oxygen molecule split into unpaired electrons and react easily with other molecules. This process is called oxidation. Antioxidants are molecules on the opposite end of the spectrum. They can donate an electron to oxidants without making themselves unstable and turn oxidants less reactive. Oxidative stress occurs when the production of oxidants exceeds the removal by body’s antioxidant systems of oxidants.

Oxidative stress has been implicated in the pathogenesis of many diseases. However, oxidants are not always enemies of the body. The editors of an international journal, Oxidant and Antioxidant Medical Science, wrote an article titled “Oxidants and Antioxidants: Friends or Foes?” (2). This article is based on their recognition that oxidants are both detrimental and beneficial to the body. For example, some of oxidants (e.g. superoxide, hydrogen peroxide and nitric oxide) do not cause indiscriminate damages to cellular components. Instead, they can play an important role in maintaining normal physiological functions as signalling molecules.

Figure - Major known oxidant/antioxidant pathways in living organisms. Many pathologic processes including inflammation, ischemia and irradiation as well as physiological functions such as cellular respiration can trigger or increase superoxide O2 production.

We often hear that regular physical activity can reduce the risk of many diseases. This is because the moderate and progressive production of oxidants works to strengthen body’s antioxidant systems, both enzymatic (e.g. superoxide dismutase, catalase, glutathione peroxidase) and non-enzymatic (coenzyme Q10, glutathione, lipoic acid). Intense and prolonged physical activity, on the other hand, can lead to the excessive production of oxidants and exhaust body’s antioxidant systems. This explains why a number of elite athletes suffer from insomnia, mood swing, cardiovascular conditions and reduced immunity. A group of Italian researchers recently published an excellent review article on this subject (3).

Finally, it is important to note that a considerable number of antioxidants have been shown to trigger a chain of oxidative reactions. Researchers at Maastricht University in the Netherlands writes (4):

Conclusion

The balance between oxidants and antioxidants in the body is essential for health. Importantly, an excessive intake or a wrong choice of antioxidant supplements may have a detrimental effect on the body. In this regard, it is noteworthy that there has been no report of an adverse effect in the use of molecular hydrogen in the human. Among possible reasons is that molecular hydrogen acts as a selective antioxidant, neutralizing only the most reactive and therefore most harmful oxidant.

References

1. Ohsawa, M. et al., 2007. Hydrogen acts as a therapeutic antioxidant by selectively reducing cytotoxic oxygen radicals. Nature Medicine, 13: 688-694.
2. Oter, S. et al., 2012. Oxidants and antioxidants: friends or foes? Oxidant and Antioxidant Medical Science, 1: 1-4.
3. Simioni, C. et al., 2018. Oxidative stress: role of physical exercise and antioxidant nutraceuticals in adulthood and aging. Oncotarget, 9: 17181-17198.
4. Bast, A. and Haenen, G.R., 2013. Ten misconceptions about antioxidants. Trends in Pharmacological Science, 34: 430-436.