Estimation of Molecular Hydrogen Consumption in the Human Whole Body After the Ingestion of Hydrogen-Rich Water
Recent studies have revealed that inhaled or ingested hydrogen gas (H2) inactivates reactive oxygen species such as hydroxyl radicals in various kinds of diseases and disorders in animal models and that H2 reduces oxidative stress-induced damage in brain, heart, and other peripheral tissues. These reports suggested that exogenous H2 is partially trapped by oxygen radicals. This study was conducted to evaluate H2 consumption after the ingestion of H2-rich water. Seven adult subjects ingested H2-rich water. The H2 content of their expired breath was measured by gas chromatography with a semiconductor. The ingestion of H2-rich water rapidly increased breath H2 content to its maximal level of approximately 36 ppm at 10 min after ingestion and thereafter decreased it to the baseline level within 60 min. Taken together with simultaneous measurements of expiratory minute volume, 59% of the ingested H2 was exhaled. The loss of H2 from the water during the experimental procedures accounted for 3% or less of the H2. H2 release from the skin surface was estimated as approximately 0.1%. Based on the remaining H2 mass balance, approximately 40% of the ingested H2 was consumed in the body. As the H2 molecule is reported to be a weak scavenger of hydroxyl radicals and is not effective against superoxide or hydrogen peroxide, the rate of hydroxyl radical production was estimated to be at least 1.0 μmol/min/m2 (equivalent to 29 nmol/min/kg), assuming that the H2 molecules were all used to scavenge hydroxyl radicals and that bacterial consumption in the alimentary tract and on the skin surface could be excluded. In summary, 59% of ingested H2 was exhaled, and most of the remainder was consumed in the body.
KeywordsAlimentary Tract Bacterial Flora Scavenge Hydroxyl Radical Colonic Fermentation Bacterial Consumption
This work was supported by the Japan Society for the Promotion of Science (Grant-in-Aid 16209020, 21240057, 21659211, 19–1063) and the Intramural Research Fund of the National Cerebral and Cardiovascular Center (22-4-5). The authors have no conflicts of interest to report. We thank all the volunteers who participated in this study.