Your body produces molecular hydrogen (H₂) every day. Bacteria in the large intestine release it when they ferment fibre and other carbohydrates that the small intestine doesn't absorb. Part of this hydrogen passes into the bloodstream and is breathed out, which is why doctors can measure it with a routine hydrogen breath test. Hydrogen atoms are also part of water and every organic molecule in the body. Since a landmark 2007 study, researchers have been investigating molecular hydrogen as a selective antioxidant. That research is active and promising, but it is not yet settled medical fact.
Hydrogen is part of every cell
Hydrogen is the most common atom in the human body. It is part of water, proteins, fats, carbohydrates and DNA, and by mass makes up roughly one-tenth of body weight.
It is also central to how cells make energy. In the mitochondria, cells pump hydrogen ions (protons) across a membrane. As those protons flow back, they drive the enzyme ATP synthase, which produces ATP, the molecule cells use for energy. This mechanism, known as chemiosmosis, earned Peter Mitchell the 1978 Nobel Prize in Chemistry [1].
It's important to be precise: these are hydrogen atoms and hydrogen ions, built into molecules. They are not the same as molecular hydrogen gas (H₂), which is two hydrogen atoms bonded together.
Your body makes hydrogen gas every day
Your large intestine is home to trillions of bacteria. When they ferment fibre and carbohydrates that weren't absorbed higher up the gut, one of the by-products is molecular hydrogen gas [2].
Not all of it stays in the gut:
- Some is used by other gut microbes.
- Some leaves the body as intestinal gas.
- Some is absorbed into the blood, travels to the lungs, and is breathed out [2].
How much hydrogen each person produces varies widely. It depends on diet and on the mix of bacteria in the gut, and it drops sharply after antibiotics or bowel preparation for colonoscopy [3].
How doctors use this: the hydrogen breath test
Because gut-produced hydrogen ends up in the breath, it can be measured. The hydrogen breath test is a standard, non-invasive clinical test used to help diagnose conditions such as lactose intolerance and small intestinal bacterial overgrowth. Gastroenterology specialists have published consensus guidance on how it should be performed and interpreted [4].
In practice, the breath test is everyday evidence that the body produces hydrogen gas and that some of it circulates in the blood.
Is hydrogen gas safe?
In 2014, the US Food and Drug Administration (FDA) reviewed a notice that hydrogen gas is "generally recognised as safe" (GRAS) as an ingredient in drinking water and beverages, at up to 2.14% by volume. The FDA's response was that it had "no questions" (GRAS Notice No. 520) [5].
This is a food-safety finding about hydrogen in drinks. It is not an approval of any health claim.
Hydrogen gas is also flammable. Any device that produces it should be used in a ventilated room, away from naked flames and sparks, following the manufacturer's instructions.
What researchers are studying
Modern research into molecular hydrogen began with a landmark 2007 study published in Nature Medicine by Ohsawa and colleagues [6]. In cell experiments, hydrogen selectively neutralised the two most reactive and damaging oxygen radicals, hydroxyl radical and peroxynitrite, while leaving other oxygen molecules the body uses for normal signalling untouched. In a rat model, breathing 2% hydrogen gas reduced brain injury after an induced stroke-like event. This "selective antioxidant" finding is why the paper became one of the most-cited in the field.
Since then, hundreds of studies have explored how hydrogen acts in the body, including whether the hydrogen produced by gut bacteria plays a protective role of its own [7]. This research is ongoing. Many studies are small, use animals or cells, or measure short-term markers, and results vary. Molecular hydrogen is not recognised as a nutrient, there is no recommended daily intake, and no health authority describes a "hydrogen deficiency".
Where hydrogen wellness products fit
Hydrogen inhalation machines and hydrogen water systems produce molecular hydrogen by splitting water (electrolysis). People use them as part of a wellness routine.
These are wellness products, not medical devices. They are not intended to diagnose, treat, cure or prevent any disease. If you have a medical condition, are pregnant, or take medication, talk to your doctor before using any new wellness product.
Frequently asked questions
- Does the human body produce hydrogen?
- Yes. Bacteria in the large intestine produce molecular hydrogen (H₂) when they ferment fibre and unabsorbed carbohydrates. Some is absorbed into the blood and breathed out [2].
- How do doctors know the body produces hydrogen?
- The hydrogen breath test measures hydrogen in exhaled breath. It is a routine test used to help diagnose lactose intolerance and small intestinal bacterial overgrowth [4].
- What started scientific interest in hydrogen as an antioxidant?
- A 2007 study in Nature Medicine by Ohsawa and colleagues found that hydrogen selectively neutralised the most reactive oxygen radicals in cell experiments, and that breathing 2% hydrogen reduced brain injury in a rat model [6].
- Is hydrogen an essential nutrient?
- No. Hydrogen atoms are part of water and all organic molecules, but molecular hydrogen gas is not classed as a nutrient and has no recommended intake.
- Is hydrogen gas safe to drink in water?
- The US FDA had "no questions" about a 2014 notice that hydrogen gas is generally recognised as safe in drinking water and beverages at up to 2.14% by volume (GRAS Notice No. 520) [5].
- Does hydrogen inhalation or hydrogen water treat disease?
- We do not make that claim. Research into molecular hydrogen is ongoing, but these products are wellness devices, not medical treatments [7].
References
- [1] The Nobel Prize in Chemistry 1978: Peter Mitchell, "for his contribution to the understanding of biological energy transfer through the formulation of the chemiosmotic theory." https://www.nobelprize.org/prizes/chemistry/1978/summary/
- [2] Levitt MD. Production and excretion of hydrogen gas in man. New England Journal of Medicine. 1969;281(3):122–127.
- [3] Gilat T, Ben Hur H, Gelman-Malachi E, Terdiman R, Peled Y. Alterations of the colonic flora and their effect on the hydrogen breath test. Gut. 1978;19(7):602–605. https://gut.bmj.com/content/19/7/602
- [4] Rezaie A, et al. Hydrogen and methane-based breath testing in gastrointestinal disorders: the North American Consensus. American Journal of Gastroenterology. 2017;112(5):775–784.
- [5] US Food and Drug Administration. GRAS Notice No. 520: Hydrogen gas. Closed 28 November 2014; FDA response: "no questions".
- [6] 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. Nature Medicine. 2007;13(6):688–694. https://pubmed.ncbi.nlm.nih.gov/17486089/
- [7] Molecular hydrogen therapy: mechanisms, delivery methods, preventive, and therapeutic application (review). PubMed Central, PMC12035766. https://pmc.ncbi.nlm.nih.gov/articles/PMC12035766/