EVOLUTION, ADAPTIVE STRESSORS AND MOLECULAR HYDROGEN

Molecular hydrogen (H2) has demonstrated therapeutic properties across numerous models. To date, the mechanism underlying the beneficial responses toH2 exposure remains elusive. The initial hypothesis that molecular hydrogen acts as a direct, selective antioxidant in vivodoes not reconcile models where H2 has shown to increase oxidative stress, nor does it explain numerous other physiological changes that have been observed throughout the literature. Some researchers have proposed that H2acts as ahormetic stress. This hypothesisdoes not reconcile H2 being non-toxic in nature, even at high doses. Hormeticstressors have contributedto evolutionary adaptations, with the absence of these stressors causing cellular dysfunction.H2 has played an intimate role in the evolution of our planets atmosphere, the evolution of mitochondria andof life on the planet.Endogenously produced H2 volumes vary dramatically between individuals and are expected to have varied through human evolution.Our cells have evolved to tolerate erratic and intermittent exposure to H2. Intermittent exogenous H2exposure yields results similar to various hormetic stressors. Continued research elucidating how H2 acts as an adaptive stressor, both through endogenous levels and exogenous supplementation, are highly warranted.