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.
Study at a glance
Human
Physically active healthy young women
Gas through a nasal cannula at 300 mL/min for 60 minutes while seated at rest · 99.8% H₂, 0.12% N₂, 0.055% O₂ and less than 0.002% CO₂.
Single 60-minute session per condition with a 7-day crossover washout
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.
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.
What kind of evidence is this?
Human
Randomized double-blind placebo-controlled crossover study
Metabolic and lipid health
Inhaled H₂
Information not yet classified
Some editorial classification fields are still pending. The source-reported outcomes and result are shown below; Hydrogenology does not infer a positive or negative signal from prose automatically.
Methods
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.
Limitations 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.
No single-study GRADE certainty rating is assigned. Read how records and evidence assessments are prepared.
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.
10 August 2026
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