Widely distributed electrolytic-generators for hydrogen-water are not fully considered for the dependencies of post-electrolytic values of the dissolved hydrogen concentration (DH) and the oxidation-reduction potential (ORP) on the properties of the pre-electrolytic water. We investigated the dependencies of DH and ORP on mineral-based hardness, temperatures and the container materials, and effects on the oral cavity by oral washing or drinking. Along with an increase in mineral-based water-hardness, DH decreased from 960 to 870 μg/L and the ORP unexpectedly increased from -460 to -320 mV. Purified water of almost zero hardness, however, caused a post-electrolytic DH as low as 80 μg/L and an ORP as high as +20 mV. Post-electrolytic DHs were not significantly changed (780-900 μg/L) upon electrolysis at 1.5-30°C and decreased at 40-50°C. The diffusion of hydrogen from the inside to the outside of the container was extremely small even after 12 hours for an aluminum- or stainless steel-made container, but not for containers made of diverse plastics. The ORP of the intact saliva was +136 mV, and decreased to +90 mV at 20 minutes after 1-minute oral-cramming of hydrogen-water, but returned to +135 mV after 60-minute leaving, showing a transient ORP-decrease in the saliva. Drinking-pause for 4 weeks after drinking hydrogen-water, however, saliva ORP, gradually but not instantly, increased to +60 to +80 mV, but upon drinking-resumption and 2 weeks thereafter, decreased again to -100 to -110 mV, suggesting that several-week hydrogen-water drinking caused a certain decrease in the saliva ORP. Thus, the present study provided the appropriate conditions such as hardness and temperatures for hydrogen-water production by the electrolytic generator, and the container materials suitable for hydrogen-water preservation. Furthermore, we clarified ORP changes of human saliva, being an indicator for human oxidative stress. The study was approved by the Medical Ethics Committee of the NPO (Non-Profitable Organization)-Corporate Japanese Center for Anti-Aging Medical Sciences (approval No. 09S02) on May 2, 2012.
Keywords: dissolved hydrogen concentration; hydrogen-water; hydrogen-water generator of the portable type; oxidation-reduction potential; oxidative stress; saliva; storage of hydrogen-water; water quality; water temperature; water-hardness.