Molecular Hydrogen Consumption in the Human Body During the Inhalation of Hydrogen Gas

Abstract

Inhaling or ingesting hydrogen (H₂) gas improves oxidative stress-induced damage in animal models and humans. We previously reported that H₂ was consumed throughout the human body after the ingestion of H₂-rich water and that the H₂ consumption rate (${\text{V}}_{{\text{H}}_{2}}$) was 1.0 μmol/min/m² body surface area. To confirm this result, we evaluated ${\text{V}}_{{\text{H}}_{2}}$during the inhalation of low levels of H₂ gas. After measuring the baseline levels of exhaled H₂ during room air breathing via a one-way valve and a mouthpiece, the subject breathed low levels (160 ppm) of H₂ gas mixed with purified artificial air. The H₂ levels of their inspired and expired breath were measured by gas chromatography using a semiconductor sensor. ${\text{V}}_{{\text{H}}_{2}}$ was calculated using a ventilation equation derived from the inspired and expired concentrations of O₂/CO₂/H₂, and the expired minute ventilation volume, which was measured with a respiromonitor. As a result, ${\text{V}}_{{\text{H}}_{2}}$ was found to be approximately 0.7 μmol/min/m²BSA, which was compatible with the findings we obtained using H₂-rich water. ${\text{V}}_{{\text{H}}_{2}}$ varied markedly when pretreatment fasting to reduce colonic fermentation was not employed, i.e., when the subject’s baseline breath hydrogen level was 10 ppm or greater. Our H₂ inhalation method might be useful for the noninvasive monitoring of hydroxyl radical production in the human body.