Effects of hydrogen-rich water on growth, redox homeostasis and hormonal, histological and immune systems in rats exposed to high cage density stress
Kuru BB, Makav M, Kuru M, Aras SY, Sarı EK, Bulut M, Alwazeer D, Bektaşoğlu F, Ölmez M, Kırmızıbayrak T, LeBaron TW. · Veterinary Medicine and Science. 2025;11(2):e70305.
What kind of evidence is this?
Preclinical
Eight-group sex-stratified rat experiment combining high-cage-density stress and H₂-rich drinking water
Other molecular hydrogen research
H₂-rich water
Not reported in this record.
Not reported in this record.
Methods at a glance
Sixty-four eight-week-old Wistar albino rats (32 female, 32 male) housed under standard or half-standard floor-area conditions.
Eight groups of eight rats each: female and male control, H₂ water, crowding stress, and crowding stress plus H₂ water.
Three months of ad-libitum water exposure; individual water consumption was not reported.
H₂-rich water was available ad libitum for three months and was remade every four hours; stressed groups were housed at half the guideline area.
The water was prepared by bubbling gas that the article calls oxyhydrogen from an electrolytic machine; this is therefore an H₂/O₂ (Brown's-gas-type) preparation step, not H₂-only gas and not inhalation by the rats.
Two litres of drinking water were bubbled for 30 minutes at 1.25 L/min total oxyhydrogen flow. The resulting dissolved H₂ was estimated, not directly measured, at approximately 1 mg/L by Henry's law/ORP.
Not directly reported because the article gives only 1,250 mL/min total oxyhydrogen flow and no measured gas composition. Under a conventional 2:1 H₂:O₂ mixture, the conditional calculated flows would be about 833 mL/min H₂ and 417 mL/min O₂ during water preparation.
O₂ was part of the reported oxyhydrogen preparation gas, but its measured percentage/flow was not stated; no gas was administered directly to the animals.
Sex-matched standard-water groups with and without crowding stress, plus H₂-water groups without stress.
Outcomes and reported result
Weekly body/terminal organ weights, thiol/disulfide balance, GSH, MDA, thyroid/cortisol/PTH/calcium markers, liver/kidney/heart histology and SOD-2 immunoreactivity.
Crowding reduced weight gain; H₂-water groups generally gained more than stressed controls. Several redox, hormonal and SOD-2 comparisons favored H₂ water, but effects were sex- and endpoint-specific: stress-related MDA was reduced in females but not males, GSH differences were not significant, and many thiol, FT3/FT4 and other subgroup comparisons were null.
The complete free PMC article, methods, main figure/table text and disclosures were checked for sex-specific groups, oxyhydrogen preparation and conditional flows, estimated dissolved concentration, positive and null subgroup results, generator support and conflicts.
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
Rat crowding model, multiple outcomes and sex-stratified comparisons, no blinded-assessment statement, estimated rather than measured dissolved H₂, unreported water intake and uncertain generator gas composition. EPOCH Energy Technology supplied the generator; TÜBİTAK ULAKBİM paid the open-access fee. Authors declared no conflicts.
Stress and growth markers in crowded rats; it does not establish effects of H₂ water on human crowding or chronic stress.
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: 40104881 · DOI: 10.1002/vms3.70305
Free full article in PubMed Central.
Complete PMC article and PubMed metadata; full-text extraction checked 9 August 2026.
2026-08-10