Hydrogen Water and Oxidative Stress: What the Studies Show

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Evidence at a glance: Very low. "Antioxidant" is the most-marketed benefit of hydrogen, and one of the least consistent in human trials. In a double-blind trial in healthy adults, the main blood markers of oxidative stress didn't differ from plain water. In a trial in people with chronic mountain sickness, hydrogen water raised a marker of oxidative damage. A meta-analysis of exercise studies found no drop in a standard oxidative-stress marker.

This page covers oxidative stress: the balance between reactive oxygen molecules and the body's antioxidant defenses, as measured by markers in blood and urine. Those markers aren't health outcomes in themselves. Of the 232 studies in our database tagged oxidative stress, 41 were in people. Of those 41, 25 reported an improvement in their main outcome, 8 had mixed results, 2 found no clear effect and the rest didn't report one; many were small, short or had no comparison group.

Where does the antioxidant idea come from?

From a 2007 study in cells and rats. It reported that hydrogen reacted with the most damaging oxygen radicals, such as the hydroxyl radical, but not with the milder ones the body uses as signals, and that breathing hydrogen reduced brain damage in rats after a stroke-like injury [7].

That "selective antioxidant" idea underlies most hydrogen research since; a 2012 review traces how hydrogen went from being considered biologically inert to being studied as an antioxidant [8]. It hasn't been confirmed as the way hydrogen acts in people.

What have human trials found?

Mixed results. Blood markers improved in some trials and not in others, and in one trial a marker of oxidative damage went up.

• 38 healthy adults, 4 weeks (double-blind). 1.5 liters a day of hydrogen water didn't change the main blood markers of oxidative stress or antioxidant capacity compared with plain water. Antioxidant capacity rose more in participants aged 30 and over, and their blood immune cells showed less cell death and lower activity in inflammation-related genes [2].
• 61 healthy workers, 8 weeks (double-blind). 1.5 liters a day of electrolyzed reduced water lowered a blood marker of oxidative stress (d-ROMs) more than mineral water did [3].
• 59 adults with chronic mountain sickness, 8 weeks (blinded). About 1 liter a day of hydrogen-rich water raised total antioxidant capacity but also raised malondialdehyde, a marker of oxidative damage, more so in people with a higher body mass index. The authors concluded it didn't reduce oxidative damage. Side effects, mostly dizziness, were reported by 50% of the hydrogen group and 37% of the placebo group [4].
• 40 physically active adults, 8 weeks. After alkaline hydrogen-enriched water, an inflammation marker (IL-6) after a maximal exercise test was lower than in the control group. The groups differed at the start, which the authors said limits what the result means [5].
• 534 adults, observational. People who had drunk electrolyzed hydrogen water for more than 6 months had lower d-ROMs than matched people who hadn't. People who choose a habit can differ in other ways, and two authors had funding from or worked for an electrolyzed-water device maker [6].
• After exercise (pooled). A 2024 meta-analysis of 6 studies with 76 healthy adults found hydrogen didn't lower a standard blood marker of oxidative stress after exercise, though antioxidant capacity rose slightly [1].

What do cell and animal studies suggest (not human evidence)?

Most of the oxidative-stress studies we index were done in cells or animals, often after sudden, severe injuries, and hydrogen often reduced markers of oxidative damage in them. Those models don't show that drinking hydrogen water changes oxidative stress in healthy people, and an antioxidant effect in a lab dish doesn't guarantee one in a person [7].

What doses and durations were studied?

No trial compared doses. The drinking trials gave about 1 to 1.5 liters a day for 4 to 8 weeks [2][3][4][5].

What don't we know yet?

Whether changes in these markers mean anything for health, and why the trials disagree.

• Markers versus outcomes. None of the trials above linked a change in an oxidative-stress marker to a health outcome.
• Hydrogen or alkalinity? Two trials used alkaline electrolyzed water, which differs from plain water in pH as well as hydrogen [3][5].
• Possible harm. In one trial, a marker of oxidative damage rose with hydrogen water [4].
• Independence. One study's authors had funding from or worked for a device maker [6].

Drafted with AI assistance and checked against each linked source by our editorial team. General information, not medical advice.