Molecular Hydrogen Benefits? What Research Says About Mitochondria

Interest in molecular hydrogen grew after a 2007 study by Ohsawa and colleagues, published in Nature Medicine. Working with cultured cells and animal models, the researchers reported that hydrogen reacted selectively with the hydroxyl radical, one of the most reactive oxygen species, while leaving other signalling molecules largely unaffected [1]. That paper prompted hundreds of follow-up studies; a 2015 review catalogued more than 300 original research articles on the biological effects of hydrogen [2].

Mitochondria generate energy through a chain of chemical reactions. A by-product of this process is a group of molecules called reactive oxygen species. In normal amounts these molecules play roles in cell signalling; in excess, the imbalance is described as oxidative stress.

Because mitochondria are a major source of reactive oxygen species, researchers have examined whether hydrogen's interaction with these molecules involves mitochondrial processes. Reviews by Ohta discuss proposed mechanisms, including selective reactivity with hydroxyl radicals and possible effects on cell signalling pathways [3, 4]. A 2017 cell-culture study by Murakami and colleagues examined a process called mitohormesis, in which a mild stress on mitochondria appears to trigger the cell's own protective responses, and reported that hydrogen influenced this process in the cells studied [5].

These findings come mainly from cell and animal studies. Laboratory results do not always carry over to people, and the mechanisms proposed are still being investigated and debated.

Studies have used several methods to deliver hydrogen: inhaling low concentrations of hydrogen gas, drinking hydrogen-rich water, bathing in hydrogen-rich water, and, in clinical research settings, injecting hydrogen-rich saline. A 2015 paper compared how drinking, injection and inhalation affect hydrogen concentrations measured in the body, finding that the route and dose change how much hydrogen reaches the bloodstream and how quickly it is cleared [6].

Human research on molecular hydrogen exists but is limited. Most studies are small, short and conducted in specific patient groups or settings, and many have not been independently replicated. For example, a 2016 first-in-human pilot study examined the feasibility and safety of hydrogen gas inhalation in a hospital setting [7]. Pilot studies of this kind are designed to test feasibility and safety, not to establish effects in the general population.

Larger, well-controlled clinical trials are needed before firm conclusions can be drawn about benefits in people. Research into hydrogen bathing is at an earlier stage than research into inhalation or drinking.

Animal studies have examined the safety of inhaled hydrogen at research concentrations [8]. Hydrogen is produced naturally in small amounts by gut bacteria and is not considered toxic at these levels. Hydrogen gas is, however, flammable at concentrations between about 4% and 75% in air. Any hydrogen equipment should be used strictly according to its manual, in a ventilated space, and away from open flames, sparks and smoking.

The honest answer is that the research is still developing. Laboratory studies have generated hypotheses about how hydrogen interacts with oxidative stress and mitochondrial processes. Human evidence remains early and limited, and no benefit in people should be regarded as established. Anyone considering hydrogen for a health reason should speak with their doctor.

For an overview of how hydrogen behaves in the body, see our article on hydrogen in the human body: /learning/hydrogen-in-the-human-body