Hydrogen Gas Inhalation Improved Intestinal Microbiota in Ulcerative Colitis: A Randomised Double-Blind Placebo-Controlled Trial
Maruyama T et al. · Biomedicines. 2025;13(8):1799.
What kind of evidence is this?
Human
Randomized double-blind placebo-controlled pilot trial
Gastrointestinal health
Inhaled H₂
Not reported in this record.
Not reported in this record.
Methods at a glance
Adults with active ulcerative colitis continuing standard treatment
10 participants: H₂ n=5, placebo n=5
4 hours/day for 8 weeks
Hydrogen in air inhaled at home for 4 hours/day
H₂ in mixed air — H₂ only was generated; this was not Brown’s gas and no O₂ stream was co-delivered.
5–6% H₂ in a total airflow of 4 L/min.
200–240 mL/min H₂, calculated as 5–6% of the reported 4,000 mL/min total flow.
No separate O₂ stream was reported; ordinary air supplied the background oxygen.
Air from a visually identical placebo machine
Outcomes and reported result
Clinical and endoscopic indices, microbiome diversity and functional-gene analyses, safety
The trial found no clear therapeutic effect on ulcerative colitis. Alpha diversity was not significant (p=0.19); beta-diversity change was reported at p=0.02. No inhalation-related adverse events were reported.
Methods, flow, main clinical and microbiome results, early stopping and funding checked in the free full text.
A reported association, difference or mechanism is not automatically a clinical benefit. Null findings, outcome type, study design and precision all matter.
Cautions and applicability
Only five participants per arm, many microbiome comparisons, standard therapies continued, and recruitment stopped after interim review because clear clinical improvement was absent. MiZ Co., the device manufacturer, funded the study.
Adults with active ulcerative colitis meeting this pilot trial’s criteria.
Not reported in this record.
Not reported in this record.
Not reported in this record.
No single-study GRADE certainty rating is assigned. Certainty is assessed by important outcome across a complete eligible evidence set, not by attaching a final grade to one source.
Sources and record status
PMID: 40868053 · DOI: 10.3390/biomedicines13081799
Open-access article.
Free full text on PMC and publisher page; identifiers cross-checked in PubMed.
2026-08-10