A new type of electrolyzed hydrogen-saturated (EHS) side is alkalized by the OH“ produeed. Our device, water was produced using a water-electrolyzing deviee however, is equipped with a special perfiuorosulfonic equipped with a special cation exchanger. Use of the acid cation-exchanging Nafion® membrane (Du Pont, El-IS water tor drinking in a feeding test with rats Tokyo) which facilitates movement of the produced H‘ elicited an antioxidative en’ect. Alter intraperitoneal (l) into the cathode side because the ionic form of our iniection of 2,2-azobis-amidinopropane dihydrochlo- membrane is H". The water thus turns to neutrality ride, urinary secretion of 8-hydroxydeoxyguanosine (approximately pH 7.5). These two processes, electrol- and hepatic formation of peroxidized lipid were ysis and cation exchange, can be carried out using the cantly lessened in rats which had received the EHS apparatus shown in Fig. 1.1'2’ The water produced is water tor one week. These results suggest the possibility saturated with hydrogen at 1.6 ppm with oxidation- that this drinking water shows an eflect in reduction ot reduction potential at -600 mV or less. oxidative stress in the body. Here we report on the antioxidative activity observed when rats were given this EHS water for drinking use. Key words: water; clectmlyzcd hydrogcn-saturatcd