Hydrogen Jelly Shows No Overall Sleep Benefit; Gut Bacteria May Explain Who Responds

For eight weeks in the first half of 2024, 44 healthy volunteers in Hiroshima ate three small packets of jelly a day, spaced at least two hours apart. Half the packets held hydrogen. The other half held only air. Neither the participants nor the researchers knew who had which. The question was whether hydrogen would help people sleep.

As a whole, it did not. A team from Hiroshima University reported that the hydrogen group showed no statistically significant improvement in sleep quality compared with the placebo group. The trial ran from January to May 2024, and the results were published in Scientific Reports on July 27, 2026. Of the 44 people who completed it, 16 were men and 28 were women, split equally between the two groups.

The idea was not arbitrary. Over the past 20 years, hydrogen has been shown in animal and clinical studies to have antioxidant, anti-inflammatory and anti-apoptotic effects, the last meaning it can interfere with programmed cell death. Earlier work found that hydrogen supplementation improved memory consolidation during sleep in mice, and improved sleep in people with long-COVID or obesity. The proposed explanation is oxidative stress. Sleep disturbances are linked to cell damage from the build-up of peroxides and free radicals, and hydrogen's antioxidant properties could counter that.

The researchers designed the trial with a further question in mind. Humans make their own hydrogen when gut microbes ferment food, and the amount varies widely from person to person. Fumiko Higashikawa, an associate professor at Hiroshima University Hospital and the study's first and corresponding author, says this variation has rarely been considered in studies of hydrogen taken from outside the body. The total daily dose in the trial was 0.9 mg. Participants logged their jelly consumption, health, medication and supplements every day, and recorded their food and drink for the three days before each clinic visit. Sleep was assessed weekly through four surveys, and stool samples taken before and after the trial gave a profile of each person's gut microbiome.

Those samples revealed a wide spread. The researchers used the combined relative abundance of four major hydrogen-producing bacterial genera as a stand-in for a person's capacity to make hydrogen. Across participants it ranged from 0.1% to 57.5%. Within the hydrogen group, the gut profiles of people who reported improved sleep differed from those who did not, and the difference seemed tied to the abundance of hydrogen producers, including taxa such as Bacteroides. Exploratory analyses suggested that people with lower levels of these bacteria saw greater improvements in sleep quality and mental stress after taking hydrogen.

Higashikawa offers an analogy: a whisper in a quiet room is easily heard, while the same whisper in a noisy room is lost. In someone whose gut produces little hydrogen, added hydrogen may stand out; in someone whose gut already produces a lot, it may not. She calls the central message of the paper that the effects of hydrogen-rich jelly may not be uniform, and that gut microbiome differences should be considered in future hydrogen research.

The finding is exploratory, and sits beside a null result for the group as a whole. The authors describe the work as a first step toward a more personalized approach to hydrogen. Their next move is to examine how breath hydrogen concentration relates to the gut microbiome, to clarify why people respond differently. They also say the work must be repeated in larger and more diverse populations using objective sleep measures, rather than the surveys used here. Higashikawa says the longer-term aim is to apply a microbiome-informed approach to other health targets and, eventually, to tailor supplement and diet choices to an individual's gut. Keishi Kanno of Hiroshima University Hospital co-authored the study, which was funded by Shinryo Corporation, the company that also supplied the jellies.