Benefits
Cholesterol and blood sugar markers (small effects)
In a 24-week randomized trial in 60 adults with metabolic syndrome in India, hydrogen-rich water (about 11 mg H2 a day) lowered total cholesterol by roughly 18 mg/dL, triglycerides by roughly 47 mg/dL, fasting glucose and HbA1c versus placebo. LDL did not change significantly and HDL fell slightly. The tablet manufacturer part-funded that trial, a later 3-month trial in 181 people found no overall difference, and a meta-analysis pooling 13 randomized trials in 757 overweight or obese adults found average reductions of only 6.7 mg/dL in total cholesterol and 3.2 mg/dL in LDL, no change in triglycerides, and a small fall in HDL. Its authors concluded those effects are too small to matter for cardiovascular risk.
Selective radical scavenging (shown in cells and rats)
In cultured cells, hydrogen reduced the hydroxyl radical, the most damaging reactive oxygen species, and did not react with hydrogen peroxide, superoxide or nitric oxide, which have signalling roles. Inhaled hydrogen then reduced brain injury in a rat stroke model. This selectivity has not been demonstrated in people drinking hydrogen water.
Blood vessel function (one 2-week trial)
In a randomized trial in 68 healthy adults, drinking 500 mL of water containing 7 ppm of hydrogen (3.5 mg) improved finger-artery endothelial function on peripheral arterial tonometry, while the placebo group did not change. The hydrogen group's own reading rose about 22 percent at 24 hours and 25 percent after 2 weeks; the difference between the two groups reached significance at both points (p=0.02). That is one small, short trial of a surrogate measure, not of heart attacks or strokes.
Inflammation markers (one trial, not replicated)
In the 24-week metabolic syndrome trial, hydrogen-rich water lowered TNF-alpha, IL-6 and C-reactive protein versus placebo. That is the main human inflammation result, and it comes from a single manufacturer-funded trial in 60 people. Work on ulcerative colitis and COPD is either in animals or uses inhaled hydrogen gas in hospital, not hydrogen water by mouth.
Exercise: less perceived effort and lactate, no endurance gain
A 2024 meta-analysis of 27 studies in 597 adults found no effect of hydrogen on VO2max, endurance exercise, 30-second anaerobic capacity or muscular strength. It did find small effects on lower-limb explosive power, on rating of perceived exertion and on blood lactate. A separate randomized trial in trained runners found no change in time to exhaustion.
Cognition: the one-year trial was negative
In a one-year randomized double-blind trial, 73 adults with mild cognitive impairment drank about 300 mL of hydrogen water or placebo daily. There was no difference between the groups on the ADAS-cog score, the trial's main measure. Only a subgroup carrying the APOE4 gene improved, which is an after-the-fact finding that needs its own trial.
Mechanism of action
Selective scavenging of hydroxyl radicals and peroxynitrite
In cultured cells, H2 reacted with •OH (hydroxyl radical, the most reactive ROS) and ONOO- (peroxynitrite) but not with H2O2 or O2•- (superoxide). If that selectivity holds in people it would reduce the most damaging ROS while preserving physiological ROS signalling, unlike typical antioxidants that may blunt adaptive responses. It has not been shown directly in humans.
Nrf2 pathway activation
H2 activates Nrf2 (nuclear factor erythroid 2-related factor 2) transcription factor — upregulating endogenous antioxidant defenses (HO-1, NQO1, GST, glutathione synthesis). Mechanism for sustained antioxidant effects beyond direct radical scavenging.
NF-κB inhibition and inflammasome modulation
H2 inhibits NF-κB nuclear translocation, reducing pro-inflammatory cytokine production (TNF-α, IL-6, IL-1β). Modulates NLRP3 inflammasome activation. Mechanism for anti-inflammatory effects observed in clinical studies.
Mitochondrial function support
H2 reduces mitochondrial ROS production while preserving electron transport chain function. Improves mitochondrial respiration and ATP synthesis. Mechanism may involve direct effects on mitochondrial membrane and indirect effects via reduced oxidative damage.
Anti-apoptotic effects via Ras-ERK1/2 and Akt pathways
H2 inactivates pro-apoptotic Ras-ERK1/2-MEK1/2 and Akt pathway elements while preserving cell survival signals. Mechanism for tissue protection in ischemic and toxic injury models.
Gut microbiome modulation
Hydrogen affects gut microbiota composition — interesting given that gut bacteria themselves produce H2 endogenously through fermentation. Supplemental H2 may modulate this signaling axis. Mechanism for some metabolic and inflammatory benefits.
Clinical trials
Randomized double-blinded placebo-controlled trial (LeBaron TW, Singh RB, Fatima G, Kartikey K, Sharma JP, Ostojic SM, Gvozdjakova A, Kura B, Noda M, Mojto V, Niaz MA, Slezak J, Diabetes Metab Syndr Obes 2020;13:889-896, doi:10.2147/DMSO.S240122).
60 adults of Indian ethnicity (30 men, 30 women, mean age 43) with metabolic syndrome, recruited in Moradabad, India, randomized to hydrogen-rich water or placebo for 24 weeks. Dose was one hydrogen-generating tablet in 250 mL of water three times daily, more than 5.5 mmol (about 11 mg) of H2 per day. Endpoints: body composition, blood lipids, glucose, inflammation and redox markers.
Versus placebo, hydrogen water lowered total cholesterol (about 18 mg/dL), triglycerides (about 47 mg/dL), fasting glucose, HbA1c, TNF-alpha, IL-6 and CRP (P<0.05). LDL did not reach significance (P=0.06), HDL fell slightly in the hydrogen group while it rose in placebo (P=0.01), and TBARS did not change (P=0.309). The manufacturer, HRW Natural Health Products, donated the tablets and part-funded the study. A later 3-month trial in 181 people found no overall difference, and the effect sizes here are two to three times larger than the average across 13 pooled randomized trials.
Laboratory study in cultured cells and in rats, not a trial in people (Ohsawa I, Ishikawa M, Takahashi K, Watanabe M, Nishimaki K, Yamagata K, Katsura K, Katayama Y, Asoh S, Ohta S. Hydrogen acts as a therapeutic antioxidant by selectively reducing cytotoxic oxygen radicals. Nat Med 2007;13(6):688-694, doi:10.1038/nm1577).
Cultured cells and rats. No human participants. The animal work used inhaled hydrogen gas, not hydrogen water by mouth.
In cultured cells, H2 reduced the hydroxyl radical (•OH) and peroxynitrite (ONOO-) but not H2O2 or superoxide (O2•-), which have signalling roles. In rats, inhaling 2 to 4 percent H2 reduced brain infarct volume after artery occlusion. This is the paper the whole selective-antioxidant idea rests on, and it is preclinical: nothing in it was measured in people, and nothing in it was given by mouth.
Narrative review article, not a study in people (Ge L, Yang M, Yang NN, Yin XX, Song WG. Molecular hydrogen: a preventive and therapeutic medical gas for various diseases. Oncotarget 2017;8(60):102653-102673, doi:10.18632/oncotarget.21130).
No participants. This is an author summary of other people's animal and human studies, most of them animal, and most using routes other than drinking water.
The review collects reports of hydrogen effects in animal models of ischemia-reperfusion injury, inflammation and metabolic disturbance, and describes proposed mechanisms including selective radical scavenging, Nrf2 activation and NF-kB inhibition. Much of the material uses inhaled gas, injected hydrogen-rich saline or hydrogen baths rather than hydrogen water by mouth. A review pools other people's results and cannot itself show that hydrogen water works.