Persistent oxidative stress is one of the major causes of most lifestyle-related diseases, cancer, and the aging process. Hydrogen can be inhaled as a gas at low concentrations (1-3%). Despite the clinical importance of oxidative damage, antioxidants have been of limited therapeutic success. Molecular hydrogen (H2) has potential as a “novel” antioxidant in preventive and therapeutic applications. H2 has several advantages as a potential antioxidant: H2 rapidly diffuses into tissues and cells, and it is mild enough neither to disturb metabolic redox reactions nor to affect reactive oxygen species (ROS) that function in cell signalling, thereby, there should be little adverse effects of consuming H2. There are several methods to consume H2, including inhaling hydrogen gas.