Researchers studied 240 people to see if working night shifts affects the helpful bacteria living in your stomach and intestines. They found that night shift work didn’t dramatically change everyone’s gut bacteria, but it did affect people who also had trouble sleeping. Workers who slept poorly and worked nights had slightly less diverse bacteria in their guts, which might matter for health. The study suggests that the combination of night shifts plus bad sleep could be more important than night shifts alone when it comes to your gut health.

The Quick Take

  • What they studied: Whether working night shifts changes the types and amounts of bacteria living in people’s digestive systems
  • Who participated: 240 adults with an average age of 42 years, mostly women (80%), about half of whom worked night shifts regularly
  • Key finding: Night shift work alone didn’t significantly change gut bacteria for most people, but workers with poor sleep quality showed less diverse bacteria in their guts compared to day workers
  • What it means for you: If you work night shifts, pay attention to your sleep quality—that may matter more than the shift itself. This is early research, so don’t make major changes yet, but it suggests sleep quality is worth protecting if you work nights

The Research Details

Scientists collected stool samples from 240 people and analyzed the bacteria in them using genetic testing. They compared night shift workers to day shift workers and looked at whether factors like sleep quality, diet, and natural sleep preferences made a difference. The researchers used statistical methods to account for age, sex, and education level so these factors wouldn’t confuse the results.

They measured two main things: how many different types of bacteria each person had (called diversity) and which specific bacteria were most common. They also looked for patterns where night shift work affected bacteria differently depending on someone’s sleep quality or eating habits.

This approach allowed them to see not just whether night shifts matter, but also whether other factors change how much night shifts affect your gut bacteria.

Understanding how work schedules affect your gut bacteria is important because your gut bacteria influence digestion, immune system function, and possibly even mood and weight. If night shifts do change your bacteria in harmful ways, it could explain why shift workers sometimes have more health problems. This study helps separate what’s actually caused by the shift work versus what’s caused by poor sleep or other factors that come with shift work.

This study has a reasonable sample size (240 people) and used modern genetic testing to identify bacteria accurately. However, the findings were not very strong statistically—most differences between groups weren’t significant. The study only looked at one point in time rather than following people over months or years. The researchers adjusted for important factors like age and sex, which strengthens the results. Some findings about specific bacteria types didn’t hold up after checking for statistical errors, which suggests those results may not be reliable.

What the Results Show

The main finding was that night shift work alone didn’t significantly change the overall diversity of gut bacteria for most people. However, when researchers looked more carefully at people with poor sleep quality, they found that night shift workers in this group had slightly less diverse bacteria compared to day workers who slept poorly.

Interestingly, people who had worked night shifts for less than 15 years showed slightly different bacteria patterns than those who never worked nights, but this difference was small. The researchers also noticed that day shift workers tended to have more of a bacteria type called Ruminococcus, while night shift workers had more Escherichia-Shigella bacteria, but these differences weren’t strong enough to be considered reliable findings.

The key insight was that sleep quality seemed to be the important factor. Night shift work only showed a clear connection to bacteria changes in people who also reported poor sleep quality.

The study found that how long someone had worked night shifts mattered somewhat—newer night shift workers showed slightly different bacteria patterns than long-term night shift workers or day workers. The researchers also looked at whether diet and natural sleep preferences (whether someone is naturally a morning or evening person) changed how night shifts affected bacteria, but these interactions weren’t strong enough to be definitive. The study suggests that individual differences in how people respond to shift work are important, but more research is needed to understand these patterns.

Previous studies on this topic have been small and limited in scope. This study is larger than most earlier research, which makes it more reliable. However, earlier studies suggested night shifts might harm gut bacteria more dramatically than this study found. The current findings suggest that the relationship between night shifts and gut bacteria is more complex than previously thought—it’s not just about the shift work itself, but about how it combines with other factors like sleep quality. This aligns with growing scientific understanding that shift work affects people differently depending on their individual circumstances.

This study only looked at people at one point in time, so we can’t tell if the bacteria changes happen because of night shifts or if people with certain bacteria types are more likely to work nights. The study included mostly women (80%), so results might not apply equally to men. Some of the bacteria differences the researchers found didn’t remain significant after checking for statistical errors, meaning those results might have been false alarms. The study didn’t measure exactly what people ate or how much they slept, which could have affected the results. Finally, we don’t know yet whether the small bacteria changes observed actually cause health problems.

The Bottom Line

If you work night shifts, prioritize getting good quality sleep—this appears to be more important than the shift work itself based on this research. Maintain consistent sleep schedules when possible, keep your sleep environment dark and cool, and consider talking to a doctor if you have persistent sleep problems. For general gut health, eat a varied diet with plenty of fiber-rich foods. However, these are general health recommendations; this study alone isn’t strong enough to make major life changes around. (Moderate confidence level)

Night shift workers, especially those with poor sleep quality, should be aware of these findings. Healthcare providers caring for shift workers might use this information when discussing health risks. People interested in gut health and how lifestyle affects it will find this relevant. However, this research is preliminary—it’s not yet strong enough to change medical treatment or be the sole basis for major decisions. People working day shifts don’t need to worry about these specific findings.

If you make changes to improve sleep quality, you might notice better sleep within days or weeks. Changes to gut bacteria diversity would likely take weeks to months to develop. Health benefits from improved sleep and gut bacteria would take longer to appear—probably months to see meaningful differences in how you feel or any health markers.

Want to Apply This Research?

  • Track sleep quality nightly using a simple 1-10 scale, noting factors like how long it took to fall asleep, number of wake-ups, and how rested you felt. Also track work shift type (night vs. day) to correlate with sleep patterns over time.
  • Set a consistent sleep schedule even on days off, and use the app to set reminders for sleep preparation 30 minutes before bed. Log any dietary changes and note which foods seem to help or hurt your sleep quality.
  • Review sleep quality trends monthly to identify patterns between shift type and sleep quality. Track any digestive symptoms (bloating, irregularity, energy levels) alongside sleep and shift data to notice personal patterns. Share this data with a healthcare provider if you have ongoing health concerns.

This research is preliminary and should not be used to diagnose or treat any medical condition. The findings show associations, not proven cause-and-effect relationships. If you have concerns about your digestive health, sleep quality, or how shift work affects your health, consult with a healthcare provider. This study was published in 2026 and represents current research, but future studies may provide different insights. Individual responses to shift work vary greatly, and what applies to the group studied may not apply to you personally.