Effects of hydrogen-rich water bath on visceral fat and skin blotch, with boiling-resistant hydrogen bubbles
Asada R, Saitoh Y, Miwa N. · Medical Gas Research. 2019;9(2):68–73.
Study at a glance
Human
Two men and two women aged 41–48 years, each assigned different skin, waist/visceral-fat or blood-marker observations.
Immersion in 40–41 °C H₂-rich bath/washbowl water for 10–15 minutes per session over one to seven months, with schedules differing by participant. · Bath/washbowl dissolved H₂ was generally reported as 175–300 μg/L (normal water <10 μg/L); the large bath contained 180–200 L. Water tests examined retention after boiling.
One to seven months depending on outcome; most full-body sessions were 10 minutes daily.
The report describes lighter/smaller photographed blotches and lower waist/visceral-fat measurements in selected participants; one participant's LDL changed from 132 to 109 mg/dL and fasting glucose from 103 to 89 mg/dL at six months. The abstract incorrectly says fasting glucose increased 13.6%, whereas its own table shows a decrease of that magnitude. No inferential clinical statistics or controlled comparison were provided.
Only four uncontrolled cases with different regimens/outcomes, subjective photographs, no sham/temperature control, lifestyle self-report, commercial bath apparatus, mechanistic speculation and an internal glucose-reporting contradiction. A Japanese anti-aging NPO grant partly supported the work; authors declared no conflicts.
What kind of evidence is this?
Human
Uncontrolled four-person collection of heterogeneous before/after bathing case observations plus water-characterization tests
Skin, wound and aging research
Other forms
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
Two men and two women aged 41–48 years, each assigned different skin, waist/visceral-fat or blood-marker observations.
Four participants total; individual outcomes were usually reported for one to three participants, without a concurrent control group.
One to seven months depending on outcome; most full-body sessions were 10 minutes daily.
Immersion in 40–41 °C H₂-rich bath/washbowl water for 10–15 minutes per session over one to seven months, with schedules differing by participant.
H₂ dissolved in bath water generated electrolytically — not classified as Brown's gas because the study did not report an H₂/O₂ gas composition, and not inhalation.
Bath/washbowl dissolved H₂ was generally reported as 175–300 μg/L (normal water <10 μg/L); the large bath contained 180–200 L. Water tests examined retention after boiling.
Each participant's own baseline only; no sham bath, ordinary-water control, randomization or blinding.
Outcomes and reported result
Photographic skin blotches/appearance, waist circumference, ultrasound-estimated visceral fat in three participants and lipid/glucose values in one participant.
The report describes lighter/smaller photographed blotches and lower waist/visceral-fat measurements in selected participants; one participant's LDL changed from 132 to 109 mg/dL and fasting glucose from 103 to 89 mg/dL at six months. The abstract incorrectly says fasting glucose increased 13.6%, whereas its own table shows a decrease of that magnitude. No inferential clinical statistics or controlled comparison were provided.
The complete free PMC article, participant-specific protocols, photographs/tables, water tests and disclosures were checked for dissolved concentration, missing flow/composition, heterogeneous outcomes, the abstract/table glucose contradiction, funding and conflicts.
A reported association, difference or mechanism is not automatically a clinical benefit.
Limitations and applicability
Only four uncontrolled cases with different regimens/outcomes, subjective photographs, no sham/temperature control, lifestyle self-report, commercial bath apparatus, mechanistic speculation and an internal glucose-reporting contradiction. A Japanese anti-aging NPO grant partly supported the work; authors declared no conflicts.
Very low-certainty cosmetic/metabolic observations; they do not establish that H₂ bathing changes skin disease, body fat, cholesterol or glucose.
No single-study GRADE certainty rating is assigned. Read how records and evidence assessments are prepared.
Sources and record status
PMID: 31249254 · DOI: 10.4103/2045-9912.260647
Free full article in PubMed Central.
Complete PMC article and PubMed metadata; full-text extraction checked 9 August 2026.
10 August 2026
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