Scientists discovered that eating too little fiber might increase anxiety and stress. In their study with mice, researchers found that a low-fiber diet disrupted the healthy bacteria in the gut and damaged the intestinal lining, which then triggered stress responses in the brain. When they gave the mice a special supplement called mannan oligosaccharides (MOS), it restored the gut bacteria, reduced inflammation, and improved anxiety symptoms. This research suggests that fiber isn’t just important for digestion—it may also play a key role in keeping your mood stable and stress levels down through a connection between your gut and brain.

The Quick Take

  • What they studied: Whether eating a low-fiber diet causes anxiety and stress, and whether a special supplement can fix the problem
  • Who participated: Laboratory mice that were fed either a normal diet or a low-fiber diet for 6 weeks
  • Key finding: Mice on a low-fiber diet showed increased anxiety-like behaviors, but when given a supplement called MOS, their anxiety improved and their gut health was restored
  • What it means for you: Eating enough fiber may help keep your mood stable and reduce anxiety. While this study was done in mice, it suggests that people should pay attention to their fiber intake as part of managing stress and emotional health. However, more research in humans is needed before we can say this definitively.

The Research Details

This was an experimental study conducted in mice to understand how diet affects the connection between the gut and the brain. Researchers divided mice into groups: some ate a normal diet with adequate fiber, while others ate a low-fiber diet for 6 weeks. They then tested the mice’s anxiety levels using standard behavioral tests. For mice showing anxiety symptoms, they gave a supplement called mannan oligosaccharides (MOS) and tracked whether their anxiety improved.

The researchers examined multiple aspects of the mice’s biology, including the types of bacteria living in their intestines, the health of their intestinal lining, inflammation levels, and brain activity related to stress. They also measured energy production in the colon and stress hormone levels.

This research approach is important because it helps identify the specific biological pathways connecting diet to mental health. By studying mice, scientists can carefully control variables and examine internal biological changes that would be difficult to study in humans. The study goes beyond just observing that low fiber causes anxiety—it explains the mechanism, showing exactly how fiber deprivation damages the gut and triggers brain changes.

This is a controlled laboratory study, which means researchers could carefully control what the mice ate and measure precise biological changes. The study examined multiple biological markers rather than relying on a single measurement, which strengthens the findings. However, because this was conducted in mice, the results may not directly apply to humans. The study also tested whether a supplement could reverse the effects, which adds credibility to the proposed mechanism.

What the Results Show

Mice fed a low-fiber diet for 6 weeks developed anxiety-like behaviors compared to mice eating normal diets. When researchers examined these anxious mice, they found several problems: their gut bacteria composition had changed significantly, their intestinal barrier (the protective lining of the gut) was damaged, and they had increased inflammation in the colon.

The low-fiber diet also disrupted the energy production system in the colon cells, which appears to be a critical problem. Additionally, the mice showed signs of increased stress hormones and brain inflammation, indicating that the gut problems were communicating with the brain and triggering stress responses.

When researchers gave the anxious mice the MOS supplement for 6 weeks, the anxiety improved significantly. The supplement restored healthy gut bacteria, reduced inflammation, repaired the intestinal barrier, and restored normal energy production in the colon. These improvements were accompanied by normalized stress hormone levels and reduced brain inflammation.

The study revealed that short-chain fatty acids (SCFAs)—beneficial compounds produced by healthy gut bacteria when they digest fiber—were reduced in the low-fiber group and restored by the MOS supplement. This suggests that SCFAs may be one of the key messengers between the gut and brain. The research also showed that the stress response system in the brain (called the HPA axis) became overactive in low-fiber mice and returned to normal with treatment.

Previous research has suggested a link between gut health and mental health, but this study provides more detailed evidence about how fiber specifically affects this connection. Earlier studies showed that gut bacteria influence mood and anxiety, but this research identifies fiber deprivation as a specific trigger and demonstrates that restoring fiber-related compounds can reverse the effects. The finding that energy metabolism in the colon is a critical link is relatively novel and adds an important piece to understanding the gut-brain connection.

This study was conducted entirely in mice, so we cannot be certain the same effects occur in humans. The study did not test different doses of the MOS supplement or compare it to other potential treatments. The research focused on anxiety-like behaviors in mice, which may not perfectly translate to human anxiety disorders. Additionally, the study did not examine whether simply eating more fiber would have the same effect as the supplement, or whether other types of fiber would work similarly. The sample size and specific number of mice used were not detailed in the abstract.

The Bottom Line

Based on this research, eating adequate dietary fiber appears to be important for both digestive and mental health. Current dietary guidelines recommend 25-30 grams of fiber daily for adults. This study suggests maintaining adequate fiber intake may help manage anxiety and stress. However, this is preliminary evidence from animal studies, and people should not rely solely on fiber to treat anxiety disorders. Those experiencing significant anxiety should consult healthcare providers. Confidence level: Moderate (animal study evidence, not yet confirmed in humans).

This research is relevant to anyone interested in the connection between diet and mental health, particularly those experiencing anxiety or stress. It’s especially important for people who eat low-fiber diets or processed foods. However, people with specific digestive conditions should consult their doctor before significantly increasing fiber intake. This research is not a substitute for professional mental health treatment.

In the mouse study, anxiety improvements appeared after 6 weeks of supplementation. In humans, dietary changes typically take 2-4 weeks to show effects on mood and stress levels, though individual responses vary. Consistent fiber intake over several weeks appears necessary for benefits.

Want to Apply This Research?

  • Track daily fiber intake (target 25-30g) and rate anxiety or stress levels on a 1-10 scale each evening. Monitor for patterns between fiber intake and mood over 4-week periods.
  • Gradually increase fiber intake by adding one high-fiber food daily (beans, whole grains, vegetables, fruits). Use the app to log fiber sources and set reminders to eat fiber-rich meals at consistent times.
  • Create a weekly report comparing average fiber intake to average stress/anxiety ratings. Track changes in sleep quality, energy levels, and mood alongside fiber consumption. Review trends monthly to identify personal patterns between diet and emotional wellbeing.

This research was conducted in mice and has not yet been confirmed in humans. While it suggests a connection between fiber intake and anxiety, it should not be used to diagnose, treat, or replace professional treatment for anxiety disorders or mental health conditions. Anyone experiencing significant anxiety should consult with a healthcare provider or mental health professional. This information is for educational purposes only and is not medical advice. Always consult with a doctor before making significant dietary changes, especially if you have digestive conditions or take medications.