Randomized, crossover clinical efficacy trial in humans and mice on tear secretion promotion and lacrimal gland protection by molecular hydrogen
Kubota M et al. · Sci Rep. 2021;11:6434.
Study at a glance
Human
Ten healthy adult participants in an acute crossover study, plus separate mouse lacrimal-gland experiments.
Ten persistent H₂-generating capsules consumed with 500 mL mineral water · The capsule-level H₂ dose was not quantified in the article.
Acute measurements through 60 minutes after ingestion
Exhaled H₂, tear stability and some dry-eye symptom measures improved after capsules. No side effects were reported; the human group was exploratory and very small.
Only 10 healthy participants, acute crossover timing, multiple ocular measures and a separate mouse model. One sponsor-author was CEO of a dry-eye product company, helped design and write the study, and the company paid participant rewards.
What kind of evidence is this?
Human
Randomized two-period crossover exploratory human study with separate mouse experiments
Eye health
H₂-rich water
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
Ten healthy adult participants in an acute crossover study, plus separate mouse lacrimal-gland experiments.
10 human participants
Acute measurements through 60 minutes after ingestion
Ten persistent H₂-generating capsules consumed with 500 mL mineral water
Oral H₂-generating supplement — H₂ was generated after ingestion; not H₂-rich water and not Brown’s gas.
The capsule-level H₂ dose was not quantified in the article.
500 mL mineral water without the H₂-generating capsules; 1–3 day crossover interval
Outcomes and reported result
Exhaled H₂, tear stability, tear secretion and subjective ocular symptoms
Exhaled H₂, tear stability and some dry-eye symptom measures improved after capsules. No side effects were reported; the human group was exploratory and very small.
Human intervention, methods, main results, funding and competing interests 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
Only 10 healthy participants, acute crossover timing, multiple ocular measures and a separate mouse model. One sponsor-author was CEO of a dry-eye product company, helped design and write the study, and the company paid participant rewards.
Healthy adults under the acute capsule protocol; not proof of treatment for diagnosed dry-eye disease.
No single-study GRADE certainty rating is assigned. Read how records and evidence assessments are prepared.
Sources and record status
PMID: 33742060 · DOI: 10.1038/s41598-021-85895-y
Open-access full text is available through PMC and the publisher.
Open-access PMC and publisher full texts plus PubMed bibliographic record.
10 August 2026
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