Is molecular hydrogen safe to drink?

Hydrogen isn't new to your body

Your gut bacteria make hydrogen every day as they break down food. A 1992 study measured about 35 mL of hydrogen a day leaving the body on a diet with no starch or fibre, and several times more after a fermentable sugar. Gut microbes also use up a lot of it.

Dissolved in water, hydrogen is stable and not flammable, as the FDA letter below notes. Flammability is a concern for cylinders of hydrogen gas, not for a drink.

What the FDA notice means

In 2014 a beverage company, MitoGene, notified the FDA that it considered hydrogen gas “generally recognized as safe” (GRAS) as an ingredient in drinking water, flavoured drinks and sodas, up to 2.14% by volume, the saturation level. It estimated that someone drinking 2 litres a day would take in about 3.2 mg of hydrogen. This is GRAS notice GRN 520.

On 28 November 2014 the FDA replied that it had “no questions”. That wording matters. The FDA's letter states that it has not made its own determination about the GRAS status, and that safety remains the company's responsibility. It is not an approval, and it says nothing about any health claim.

What the researchers tested

A Japanese team ran three standard toxicology tests on neutral-pH electrolysed hydrogen water containing about 0.9–1.1 ppm of hydrogen.

First, an Ames test, which checks whether something causes mutations in bacteria, using five bacterial strains, with and without liver enzymes. Second, a chromosome test in hamster lung cells. Third, rats were given 20 mL of the water per kg of body weight every day for 28 days. Their weight, blood, urine, organs and tissues were then checked.

What they found

There were no mutations in any bacterial strain and no chromosome damage in the cells. The rats showed no treatment-related changes in behaviour, weight, food intake, blood, urine, organ weights or tissue under the microscope.

The highest dose tested was the “no observed adverse effect” level. The authors say this is consistent with a 60 kg adult safely drinking up to at least 1.2 litres a day.

“

“No questions” means the FDA didn't challenge the company's safety conclusion. It is not an approval.

What human studies add

A 2015 review of 321 hydrogen studies reported no toxic effects to the authors' knowledge, while noting there may be effects not yet found. A 2024 systematic review described hydrogen-rich water as “mostly considered safe, with no to minimal side effects”, and called for bigger, longer trials.

In one 8-week trial where 20 adults drank 1.5–2 litres a day, made with a magnesium stick, there were a few mild events possibly related to it: loose stools in three people, plus one case each of more frequent bowel movements, heartburn and headache. The magnesium may play a part. If your hydrogen comes from magnesium tablets, the magnesium counts toward the 350 mg a day upper limit the US National Institutes of Health sets for supplemental magnesium in adults, so check the label.

At the extreme end, commercial deep-sea divers in the 1990s breathed gas mixes containing about 49% hydrogen at huge pressures. The problems seen there were the effects of breathing dense gas at depth, not poisoning, and it's far beyond anything in a glass of water.

What this study doesn’t show

• It tested one electrolysed water in bacteria, cells and rats, not in people.
• The rat study lasted 28 days, so it can't speak to drinking it every day for years.
• There is little or no research for pregnancy, breastfeeding or children. Ask your doctor first.

Sources

1. [1]Saitoh Y, Harata Y, Mizuhashi F, Nakajima M, Miwa N. Biological safety of neutral-pH hydrogen-enriched electrolyzed water upon mutagenicity, genotoxicity and subchronic oral toxicity.Toxicology and Industrial Health 26(4):203–216, 2010
2. [2]U.S. Food and Drug Administration. GRAS Notice No. 520: Hydrogen gas (MitoGene Beverage Company). Response: FDA has no questions.GRAS Notice Inventory, closed 28 November 2014
3. [3]U.S. Food and Drug Administration. About the GRAS Notification Program.fda.gov
4. [4]Nakao A, Toyoda Y, Sharma P, Evans M, Guthrie N. Effectiveness of hydrogen rich water on antioxidant status of subjects with potential metabolic syndrome: an open label pilot study.Journal of Clinical Biochemistry and Nutrition 46(2):140–149, 2010
5. [5]Ichihara M, et al. Beneficial biological effects and the underlying mechanisms of molecular hydrogen: comprehensive review of 321 original articles.Medical Gas Research 5:12, 2015
6. [6]Dhillon G, et al. Hydrogen Water: Extra Healthy or a Hoax? A Systematic Review.International Journal of Molecular Sciences 25(2):973, 2024
7. [7]Abraini JH, Gardette-Chauffour MC, Martinez E, Rostain JC, Lemaire C. Psychophysiological reactions in humans during an open sea dive to 500 m with a hydrogen-helium-oxygen mixture.Journal of Applied Physiology 76(3):1113–1118, 1994
8. [8]Christl SU, Murgatroyd PR, Gibson GR, Cummings JH. Production, metabolism, and excretion of hydrogen in the large intestine.Gastroenterology 102(4 Pt 1):1269–1277, 1992
9. [9]NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals.ods.od.nih.gov

This article is an educational summary of published research on molecular hydrogen. It is not medical advice, and these statements have not been evaluated by the Food and Drug Administration. OG Hydro products are not intended to diagnose, treat, cure, or prevent any disease. Talk to a qualified healthcare professional before changing your routine.