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

A jelly packet containing hydrogen, or in half the cases just air, was eaten three times a day for eight weeks by 44 adults in Hiroshima. The question was simple: would it help them sleep? The answer, published in Scientific Reports, is that overall it did not.

The trial was led by Hiroshima University and ran from January to May 2024. It was randomized, double-blind and placebo-controlled. Of the 44 participants who finished, 16 were men and 28 were women, split equally between the hydrogen group and the placebo group. Each person ate three sealed packets of jelly a day, spaced more than two hours apart. The hydrogen group received a total of 0.9 mg of hydrogen daily, while the placebo group got air.

The researchers kept close records. Participants logged their jelly consumption, health, medications and supplements every day, and recorded all food and drink for the three days before each clinic visit. Sleep quality was measured weekly with four surveys, and fecal samples were collected before and after the trial to profile each person's gut microbiome.

The idea behind the study had a track record. Over the past 20 years, hydrogen has been reported to have antioxidant, anti-inflammatory and anti-apoptotic effects in animal and clinical studies. Hydrogen supplementation has been tied to better memory consolidation during sleep in mice, and to better sleep quality in people with long COVID or obesity. Sleep disturbance is linked to oxidative stress, the cell damage caused by a buildup of peroxides and free radicals, which is where hydrogen's antioxidant action was expected to matter.

Yet in the main comparison, nothing separated the groups. "In the overall analysis, there was no statistically significant difference in sleep improvement between the hydrogen group and the placebo group," said Fumiko Higashikawa, associate professor (special designation) at Hiroshima University Hospital and the study's first and corresponding author.

The more interesting result came from exploratory analyses. Humans make hydrogen themselves through gut microbial fermentation, and the capacity varies widely. The researchers used the combined relative abundance of four major hydrogen-producing bacterial genera as a proxy for that capacity. Across participants it ranged from 0.1% to 57.5%. Participants with lower levels of these bacteria showed greater improvements in sleep quality and mental stress after taking hydrogen. Within the hydrogen group, people classed as improved and not improved also differed in their microbiome profiles, with hydrogen-producing taxa such as Bacteroides appearing to matter.

Higashikawa offered a metaphor: hydrogen may be like a whisper in a room. In a quiet room, meaning a gut that makes little hydrogen, a small addition may be noticed. In a noisy room, where the microbiome already produces a lot, the same whisper may be hard to detect. She said the central message is that the effects of hydrogen-rich jelly may not be uniform across individuals.

The subgroup findings are exploratory, drawn from a small trial, and sleep was measured by surveys rather than objective tools. The next steps are to study the relationship between breath hydrogen concentration and the gut microbiome, and to repeat the work in larger, more diverse groups with objective sleep measures. Higashikawa said the team hopes to extend the approach beyond sleep to other health targets, with the long-term aim of tailoring supplements and diets to a person's gut microbiome.