Molecular hydrogen inhalation modulates resting metabolism in healthy females: findings from a randomized, double-blind, placebo-controlled crossover study
Grepl P et al. · Med Gas Res. 2025;15(3):367–373.
What kind of evidence is this?
Human
Randomized double-blind placebo-controlled crossover study
Metabolic and lipid health
Inhaled H₂
Not reported in this record.
Not reported in this record.
Methods at a glance
Physically active healthy young women
20 participants; mean age 22.1 years
Single 60-minute session per condition with a 7-day crossover washout
Gas through a nasal cannula at 300 mL/min for 60 minutes while seated at rest
H₂ alone at high source-gas purity — not Brown’s gas.
99.8% H₂, 0.12% N₂, 0.055% O₂ and less than 0.002% CO₂.
299.4 mL/min H₂, calculated as 300 mL/min total source-gas flow × 99.8% H₂.
0.165 mL/min O₂, calculated as 300 mL/min × 0.055% O₂; this is a trace constituent, not supplemental oxygen.
Ambient air through a modified generator at 300 mL/min
Outcomes and reported result
Respiratory exchange ratio, ventilation, indirect-calorimetry measures and estimated substrate use
H₂ inhalation lowered respiratory exchange ratio and ventilation across intervals, interpreted as greater resting fat oxidation. This was an acute resting physiological study, not a clinical outcome trial.
Gas composition, flow, methods, results, funding and conflict statement checked in the open-access full text; independent appraisal remains incomplete.
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
Small acute study in healthy young women, using surrogate metabolic outcomes. One author was an external research consultant to H2 Global Group; Palacký University support was reported.
Healthy physically active young women resting under the reported laboratory protocol.
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: 39923133 · DOI: 10.4103/mgr.MEDGASRES-D-24-00085
Open-access full text is available through PMC.
Open-access PMC full text and PubMed bibliographic record.
2026-08-10