Of all the conditions studied with molecular hydrogen, Parkinson’s disease has the most complete evidence trail. Not the largest, and not the most positive, but the most complete: a small pilot trial with a striking result, a properly powered confirmatory trial designed to test it, and a published outcome for that confirmatory trial. Very few supplement questions get that far.
The reason it is worth reading in full is that the story does not end where the marketing copy stops. This page walks the whole sequence, in order, including the part that did not work.
Why anyone tested hydrogen in Parkinson’s at all
Oxidative stress is implicated in the progression of Parkinson’s disease, and molecular hydrogen behaves as a selective antioxidant that reacts with hydroxyl radical rather than scavenging useful signalling molecules indiscriminately[1]. Hydrogen-dissolved water reduced oxidative stress and improved Parkinson’s features in animal models before any human work began[2].
Parkinson’s was also one of the most heavily studied conditions in the preclinical hydrogen literature. A 2012 review counted 63 disease models and human diseases studied to that point, with two separate rodent models of Parkinson’s among them[3]. So by the time human trials started, the animal case was unusually well developed.
The 2013 pilot trial
The first human test was a placebo-controlled, randomized, double-blind, parallel-group pilot study in Japanese patients with levodopa-medicated Parkinson’s disease[2]. Participants drank 1,000 millilitres per day of hydrogen water or pseudo water for 48 weeks.
The outcome measure was the total Unified Parkinson’s Disease Rating Scale score, usually shortened to UPDRS. It is the standard instrument in the field, combining motor examination, activities of daily living and mental state into a single number, where a rising score means worsening disease.
Total UPDRS scores in the hydrogen group improved, with a median change of minus 1.0 and a mean of minus 5.7 with a standard deviation of 8.4[2]. Scores in the placebo group worsened, with a median change of plus 4.5 and a mean of plus 4.1 with a standard deviation of 9.2. The difference between groups was significant at p less than 0.05.
That is a genuinely interesting result, because the two groups moved in opposite directions over 48 weeks in a progressive disease. It is also a result built on 9 patients in the hydrogen group and 8 in the placebo group. The authors said so themselves, writing that the difference was significant “despite the minimal number of patients and the short duration of the trial”[2].
Note also what the standard deviations are doing. A mean change of minus 5.7 with a standard deviation of 8.4 means individual patients varied far more than the average moved. With 9 people, one or two unusual responders can carry the whole result.
The confirmatory trial
To their considerable credit, the same group did the thing that most of the supplement world never does: they ran a larger, longer trial specifically designed to confirm or refute their own pilot, and they registered it publicly in advance.
The protocol and baseline characteristics were published separately in 2016, before the results were known[4]. That paper is fully public and its numbers are worth stating precisely, because they show how much bigger the second attempt was.
178 participants with Parkinson’s disease were enrolled across 14 hospitals and randomized[4]. Mean age was 64.2 years with a standard deviation of 9.2, and mean baseline total UPDRS was 23.7 with a standard deviation of 11.8. 154 participants were on levodopa medication and 24 were not, with a mean daily levodopa dose of 344.1 milligrams and a mean total levodopa equivalent dose of 592.0 milligrams.
The hydrogen group drank 1,000 millilitres per day of hydrogen water and the placebo group drank normal water[4]. The pre-registered primary endpoint was the change in total UPDRS score from baseline to week 72, with additional assessments at weeks 8, 24 and 48. The trial was registered as UMIN000010014.
Two design details matter. First, the trial ran to 72 weeks rather than the pilot’s 48, so a slower-emerging benefit had room to appear. Second, it included patients not taking levodopa, whereas the pilot was restricted to levodopa-medicated patients.
What the confirmatory trial found
It did not reproduce the pilot. On the pre-registered primary endpoint, the change in total UPDRS score from baseline to week 72, there was no significant difference between the hydrogen water group and the placebo group[5].
One point of transparency about this page. The 2018 result was published as a brief item in the journal’s “Letters: New Observations” section, and unlike every other study cited here it has no abstract in the PubMed record. That means the exact effect sizes, confidence intervals and p-values are not available from a source this page can verify directly, and none are quoted above. What is stated is the primary-endpoint outcome and nothing more. Every hard number in the section before this one comes from the 2016 protocol paper, which is fully public.
This is the most important paragraph on the page, so it is worth being blunt about what it means. A small trial found a benefit. A trial roughly ten times larger, running fifty percent longer, run by the same investigators, testing the same dose of the same product, did not. When those two disagree, the larger trial is the more reliable answer. That is not a technicality, it is the entire reason the larger trial was run.
The inhalation attempt
There was one further attempt, using the other delivery route. A placebo-controlled, randomized, double-blind, parallel-group pilot study tested hydrogen gas inhalation in Japanese patients with Parkinson’s disease on levodopa[6].
Twenty participants meeting Movement Disorder Society criteria were enrolled. They inhaled 6.5 volume percent hydrogen gas in 2 litres per minute of mixed air, or placebo air, for 16 weeks, twice a day for one hour each time[6].
There were no significant differences in the change in total MDS-UPDRS score from baseline to week 16 between the hydrogen and placebo-air groups, by Mann-Whitney U test at p greater than 0.05[6]. No adverse events were seen. The authors concluded that inhalation of molecular hydrogen gas was safe but did not show any beneficial effects.
Two caveats cut in opposite directions and both should be stated. Against the null result: five of the twenty participants were excluded for deviating from the protocol with a total inhalation time under 112 hours, which leaves a very small analysed sample and makes the trial underpowered to detect a modest effect. The authors also found that compliance decreased with older age, higher daily levodopa dose, and higher scores on the PDQ-39 emotions items, at p less than 0.05.
In favour of taking it seriously: it points the same direction as the larger drinking trial, and a null result that agrees with another null result is more informative than one on its own.
One disclosure worth making because the paper makes it. The 2021 inhalation paper carries a declared conflict-of-interest statement in which several authors report lecture fees and departmental endowments from pharmaceutical companies[6]. Declaring it is the correct behaviour and it does not invalidate the finding. It is mentioned here because a reader assessing evidence should know it, and because a null result from investigators with industry ties is, if anything, harder to dismiss than a positive one.
How to read the sequence as a whole
The honest summary is that hydrogen water for Parkinson’s disease was a promising hypothesis that was tested properly and did not hold up.
That sequence is what good evidence looks like when it goes against the product. A pilot generates a signal, a larger pre-registered trial tests it, the larger trial comes back negative, and a third trial using a different delivery route also comes back negative. Nothing here suggests fraud or sloppiness. Small trials producing effects that vanish in larger ones is one of the most common patterns in all of clinical research, and it is exactly why larger trials get run.
It is worth noticing that the marketing use of this literature almost always stops at 2013. If you have seen hydrogen water promoted for Parkinson’s, check whether the citation is the pilot study. It usually is.
If you or someone in your family has Parkinson’s
Parkinson’s disease is a serious progressive neurological condition, and its treatment belongs with a neurologist. Levodopa and the other established therapies have decades of evidence behind them. Nothing on this page is a reason to change, delay or stop any of it, and the trials above were all conducted in patients who continued their normal medication.
Across all three trials, hydrogen was well tolerated and no adverse events were reported in the inhalation study[6]. Safety is not the problem here. Efficacy is. The reasonable conclusion is that hydrogen water is unlikely to do harm and, on the best available evidence, unlikely to help the course of Parkinson’s disease.
Anyone considering it anyway should raise it with the treating neurologist first, mostly so that it is documented alongside the actual treatment plan rather than running in parallel to it.
The bottom line
A 2013 pilot trial in 17 patients found that hydrogen water improved total UPDRS scores over 48 weeks while placebo worsened, at p less than 0.05[2]. A pre-registered confirmatory trial in 178 patients across 14 hospitals, running to 72 weeks, found no significant difference on its primary endpoint[4][5]. A separate trial of hydrogen gas inhalation over 16 weeks also found no beneficial effect[6].
Hydrogen appears safe in this population. On the current evidence it does not appear effective for Parkinson’s disease, and the strongest single study on the question is the one that says so.
References
- Hydrogen acts as a therapeutic antioxidant by selectively reducing cytotoxic oxygen radicals. Nature Medicine, 2007
- Pilot study of H2 therapy in Parkinson’s disease: a randomized double-blind placebo-controlled trial. Movement Disorders, 2013
- Molecular hydrogen as an emerging therapeutic medical gas for neurodegenerative and other diseases. Oxidative Medicine and Cellular Longevity, 2012
- A randomized double-blind multi-center trial of hydrogen water for Parkinson’s disease: protocol and baseline characteristics. BMC Neurology, 2016
- Randomized, double-blind, multicenter trial of hydrogen water for Parkinson’s disease. Movement Disorders, 2018
- Randomized double-blind placebo-controlled trial of hydrogen inhalation for Parkinson’s disease: a pilot study. Neurological Sciences, 2021
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Content is for informational purposes only and is not medical advice; consult a qualified healthcare provider before starting any supplement. As an Amazon Associate we earn from qualifying purchases.
