Hydrogen-rich water (HRW) has been studied for cardiovascular, metabolic, and exercise outcomes for years. The gut microbiome is a newer frontier. A 2021 narrative review in the Journal of Functional Foods, authored by Sergej M. Ostojic, brought together the small body of evidence available at the time and asked a focused question: does drinking molecular hydrogen actually change the composition or function of the bacteria living in our intestines?
What the review examined
Ostojic synthesised the available pre-clinical and clinical evidence on HRW and gut microbiota — a handful of rodent studies and one human randomised controlled trial, all published from 2018 onwards. The framing is mechanistic: hydrogen can be both produced and consumed by gut bacteria, which makes the intestine a natural site of action for exogenous molecular hydrogen.
Feeding hydrogen-producing bacteria
Several studies suggested HRW shifts the microbial balance toward bacteria that themselves produce endogenous H2, including species that contribute to gut barrier integrity. The result is a small but consistent enrichment of bacterial groups associated with healthier microbiome profiles.
Upregulation of butyrate-producing species
Butyrate — a short-chain fatty acid produced when gut bacteria ferment fibre — is one of the most important molecules for intestinal health and barrier function. The review highlights that across the available studies, HRW intake was associated with an upregulation of butyrate-producing bacteria, which may partly explain its observed gut-protective effects.
Protecting the intestinal barrier
In rodent models of gut microbiota disturbance, HRW improved clinical features such as diarrhoea rate, weight loss, and fluid loss, and protected the integrity of the intestinal barrier. These effects are consistent with H2‘s broader role in dampening oxidative stress and inflammation in tissue.
What it means in practice
This is an early-stage field. With only one human RCT in the review, no claims about specific clinical outcomes can be drawn for individual readers. What the review does establish is a plausible mechanism and a consistent direction of effect across the small evidence base — enough to take HRW seriously as a topic for further microbiome research, not enough to position it as a treatment.
Citation: Ostojic, S.M. (2021). Hydrogen-rich water as a modulator of gut microbiota? Journal of Functional Foods, 78, 104360. DOI: 10.1016/j.jff.2021.104360
