Alkaline-electrolyzed reduced water (ERW) has been credited with numerous health benefits, though many of these claims are tied to unscientific or misleading concepts. Proposed explanations for its effects have ranged from legitimate properties like its negative oxidation-reduction potential (ORP), alkaline pH, and dissolved hydrogen gas, to more questionable ideas such as altered water structures, micro-clusters, free electrons, and active hydrogen. This pseudoscientific marketing has hindered ERW’s acceptance in mainstream science. However, extensive in vitro and in vivo research has gradually debunked these unverified theories, ultimately confirming that molecular hydrogen (H₂) is the true source of ERW’s health benefits and its negative ORP. This article outlines the historical development of ERW research and presents evidence showing that H₂ alone accounts for its biological effects—without needing to rely on speculative or metaphysical explanations. It also stresses the importance of measuring the actual hydrogen concentration in ERW to ensure it aligns with doses proven effective in clinical studies.

Alkaline-electrolyzed reduced water (ERW) has been linked to various health benefits, though many early claims were based on unproven concepts like micro-clusters and altered water structures. These pseudoscientific ideas led to skepticism in mainstream science. However, extensive in vitro and in vivo research has confirmed that molecular hydrogen (H₂) is the sole active component responsible for ERW’s therapeutic effects and negative ORP. This review summarizes the research progression and emphasizes that ERW’s benefits can be explained by known biological actions of H₂, without relying on implausible theories. Accurate measurement of hydrogen concentration is essential for aligning ERW with effective clinical outcomes.