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.