Numerous benefits have been attributed to alkaline-electrolyzed-reduced water (ERW). Sometimes these claims are associated with easily debunked concepts. The observed benefits have been conjectured to be due to the intrinsic properties of ERW (e.g., negative oxidation-reduction potential (ORP), alkaline pH, H2 gas), as well enigmatic characteristics (e.g., altered water structure, microclusters, free electrons, active hydrogen, mineral hydrides). The associated pseudoscientific marketing has contributed to the reluctance of mainstream science to accept ERW as having biological effects. Finally, through many in vitro and in vivo studies, each one of these propositions was examined and refuted one-by-one until it was conclusively demonstrated that H2 was the exclusive agent responsible for both the negative ORP and the observed therapeutic effects of ERW. This article briefly apprised the history of ERW and comprehensively reviewed the sequential research demonstrating the importance of H2. We illustrated that the effects of ERW could be readily explained by the known biological effects of H2 and by utilizing conventional chemistry without requiring any metaphysical conjecture (e.g., microclustering, free electrons, etc.) or reliance on implausible notions (e.g., alkaline water neutralizes acidic waste). The H2 concentration of ERW should be measured to ensure it is comparable to those used in clinical studies.
Keywords: alkali ion water; alkaline water; alkaline-ionized water; alkaline-reduced water; electrolyzed–reduced water; functional water; hydrogen water; ionized water.