Sleep problems are not always just about stress or caffeine. Explore the possible two-way relationship between sleep and the gut microbiome and the everyday habits that support both.
Exhausted, but still unable to sleep?
Your body feels tired, yet you struggle to fall asleep once you get into bed. You wake during the night, or too early in the morning, and still feel unrefreshed when it is time to start the day.
When this happens repeatedly, stress, caffeine and late-night screen use are often the first things that come to mind. These are important factors, but researchers are also exploring another possible piece of the puzzle: the gut microbiome.
One distinction matters from the outset: poor sleep does not necessarily mean your gut microbiome is “out of balance”, and improving gut health is not a proven cure for insomnia. Sleep is influenced by many factors, including daily routines, work schedules, emotional wellbeing, medications and underlying sleep disorders. The gut microbiome is one part of this wider picture—not a single explanation for sleep difficulties.
How are the gut and sleep connected?
The gut and brain do not work in isolation. They communicate through a network involving nerve signals, immune responses, hormones and substances produced by gut microorganisms. This network is commonly called the gut–brain axis.
Researchers are investigating how microbial metabolites, including short-chain fatty acids and changes in tryptophan metabolism may interact with inflammation, stress responses and sleep regulation. Sleep disruption and changes in daily rhythms may, in turn, influence the gut environment.
This has led to the idea of a “gut–sleep axis”: a possible two-way relationship in which sleep affects the gut microbiome, while the microbiome may contribute to processes involved in sleep.
However, the strength of the evidence varies. Animal and mechanistic studies help explain possible pathways, but human studies do not yet establish a simple, predictable chain from a particular gut bacterium to insomnia—or from changing that bacterium to better sleep.
If most serotonin is made in the gut, can probiotics help us sleep?
You may have heard that most of the body’s serotonin is produced in the gut. More precisely, much of it is made by specialised cells in the intestinal lining called enterochromaffin cells—not directly by “good bacteria”. Gut microorganisms can influence this process through their metabolites and their effects on tryptophan availability.
There is another important distinction: serotonin produced in the gut does not cross the blood–brain barrier to become serotonin in the brain. Gut microbes may influence brain signalling indirectly, but “more gut serotonin” does not automatically mean better sleep.
Tryptophan is an amino acid involved in the production of serotonin and melatonin. Nevertheless, this biological connection does not prove that a particular probiotic or a microbiome test can increase melatonin, improve deep sleep or treat insomnia. Researchers are still investigating which microbial pathways matter, in whom, and under what conditions.
What does the research actually show?
People with sleep disturbances may have different gut microbiome patterns
A systematic review and meta-analysis published in 2026 included data from 53 studies in its quantitative analysis. It found lower gut microbial alpha diversity in people with sleep disturbances than in comparison groups. Alpha diversity describes the variety of microorganisms within an individual sample, although different measures capture different aspects of that variety.
The review also suggested that some microbial changes may be shared across different sleep disorders. However, the findings were exploratory, and control for confounding factors was limited. Importantly, after adjustment for possible publication bias, the association for one commonly used diversity measure—the Shannon index—was no longer statistically significant.
The takeaway is not that researchers have identified a single “bad bacterium” responsible for poor sleep. Rather, they have observed patterns that warrant further investigation.
Microbial diversity alone does not tell the whole story
A 2024 study involving 159 Korean adults found no direct relationship between sleep quality and alpha diversity. However, the researchers observed differences in the overall structure of the microbial community between better and poorer sleepers, as well as associations involving certain estimated metabolic pathways.
This suggests that the relationship may involve more than how many types of microorganisms are present. Their potential functions may also matter. Still, these associations do not establish that the microbiome caused the differences in sleep quality.
Severe short-term sleep restriction can affect some microbial measures
In a controlled crossover study, 19 healthy young men underwent two conditions: three consecutive nights with a two-hour sleep opportunity each night, and a comparison condition with a seven- to nine-hour sleep opportunity. Diet and physical activity were controlled.
During sleep restriction, microbial richness measured using amplicon sequence variants—distinct DNA sequence variants detected by the analysis—was approximately 21% lower. However, two other commonly used diversity measures, overall microbial community structure and measured intestinal permeability did not differ significantly between conditions.
This was a small study involving unusually severe sleep restriction in healthy young men. Its findings should not be generalised to every person, to chronic insomnia, or to an occasional late night. It does not justify claims that one night of poor sleep inevitably causes “leaky gut”.
Taken together, these studies point to a complex relationship rather than a single microbiome score that can explain how well someone sleeps.
Supporting sleep and gut health: start with sustainable habits
The practical starting point is regular, adequate sleep—not trying to “fix” your microbiome first. For adults aged 18–60, the general recommendation is at least seven hours of sleep per night, although individual needs vary. Sleep quality and consistency also matter.
1. Keep a reasonably consistent sleep schedule
Aim for similar bedtimes and wake-up times across the week, while allowing enough time for sleep. A regular schedule helps support the body’s sleep–wake rhythm.
2. Review late meals, alcohol and caffeine
Avoid large meals and alcohol close to bedtime, and consider limiting caffeine in the afternoon or evening. These are established sleep-supporting habits and may also help you avoid digestive discomfort at night.
3. Include a variety of fibre-containing foods
Beans, vegetables, fruit, whole grains, nuts and seeds can contribute different sources of fibre to a varied diet. Rather than treating one food as a sleep remedy, focus on an overall eating pattern you can maintain.
If you have a gastrointestinal condition or require a specialised diet, discuss dietary changes with a doctor or registered dietitian.
4. Consider how your daily routine affects sleep
Shift work, long working hours and irregular schedules can make adequate sleep more difficult. Where possible, plan a realistic routine that gives sleep a protected place in your day, rather than leaving it to whatever time remains.
5. Make room for daytime activity and a calmer evening
Regular physical activity, time outdoors and a relaxing wind-down routine are practical ways to support sleep. Reducing bright light and stimulating screen use before bedtime may also help.
6. Do not treat probiotics as a substitute for insomnia care
Research into microbiome-based approaches is still developing. The possible effects of one probiotic strain or formulation should not be assumed to apply to all products—or to everyone with sleep difficulties. Persistent insomnia needs an appropriate assessment, not simply a supplement recommendation.
What can gut microbiome testing tell you?
Gut microbiome testing provides information about the microorganisms detected in a stool sample. Depending on the method, it may also describe microbial genes or estimated functional potential.
GUTolution combines gut microbiome analysis with personalised dietary, probiotic and lifestyle guidance to help you explore your microbiome. However, testing cannot determine why you sleep poorly or confirm that a particular intervention will improve your sleep.
Want to learn more about your gut microbiome? Discover GUTolution’s gut microbiome test and explore personalised guidance for your everyday dietary and lifestyle choices.
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Start with the everyday foundations
Supporting sleep and gut health starts with sufficient sleep, consistent routines, a varied diet, regular activity and time to unwind. If sleep difficulties persist or affect daily life, consult a healthcare professional.
This article is for general educational purposes. Gut microbiome testing does not diagnose or treat insomnia and cannot replace professional medical assessment.
Reference:
Li J, et al. Gut microbiota alterations in sleep disturbances: A systematic review and meta-analysis. Sleep Medicine Reviews. 2026.
Seong HJ, Baek Y, Lee S, Jin H-J. Gut microbiome and metabolic pathways linked to sleep quality. Frontiers in Microbiology. 2024;15:1418773. doi:10.3389/fmicb.2024.1418773.
Karl JP, Whitney CC, Wilson MA, et al. Severe, short-term sleep restriction reduces gut microbiota community richness but does not alter intestinal permeability in healthy young men. Scientific Reports. 2023;13:213. doi:10.1038/s41598-023-27463-0.
(Author: Chloe Chan)
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