Scientists are discovering that the food you eat doesn’t just affect your body—it can also change your mood and mental health. Your gut contains trillions of tiny organisms called bacteria that influence your brain through something called the gut-brain connection. This review looked at research about how different types of diets, along with special foods and supplements, might help reduce anxiety and depression. The evidence suggests that eating more fiber, fermented foods, and making other dietary changes could help improve mental health, especially for people with mild anxiety or depression. However, scientists say we need more research to fully understand exactly how this connection works.

The Quick Take

  • What they studied: How different types of diets and gut bacteria affect anxiety and depression symptoms
  • Who participated: This was a review of many existing studies rather than a single study with participants. Researchers looked at findings from randomized controlled trials and observational studies involving people with anxiety and depression
  • Key finding: Multiple studies suggest that changing your diet—especially eating more fiber and fermented foods—may help reduce anxiety and depression by changing the bacteria in your gut
  • What it means for you: If you struggle with mild anxiety or depression, dietary changes might be worth trying alongside other treatments. However, this should not replace professional mental health care, and more research is still needed to confirm these benefits

The Research Details

This research is a review, which means scientists looked at and summarized findings from many different studies that were already completed. They examined research on several types of diets including high-fiber diets, diets with fermented foods (like yogurt and sauerkraut), ketogenic diets (very low carb), and calorie-restricted diets. They also looked at studies on prebiotics (foods that feed good bacteria) and probiotics (supplements containing good bacteria).

The researchers focused on studies that measured how these dietary changes affected anxiety and depression. They looked at both observational studies (where researchers watch what people eat and track their mood) and randomized controlled trials (where some people are given a dietary intervention and others are not, to compare results). This approach allowed them to see patterns across many different research projects and identify what the overall evidence suggests.

By reviewing many studies together, researchers can see the bigger picture of how diet affects mental health. Individual studies might have small sample sizes or mixed results, but when you look at patterns across many studies, clearer trends emerge. This type of review helps doctors and patients understand what dietary changes have the most evidence supporting them for mental health benefits.

This review summarizes existing research rather than conducting a new study. The quality of the conclusions depends on the quality of the studies reviewed. The authors note that research in this area has challenges because different studies use different methods and measure things differently. Many studies reviewed were observational (watching what people naturally eat) rather than randomized controlled trials (the gold standard for proving cause and effect). The authors acknowledge that more rigorous research is needed to fully understand these connections.

What the Results Show

Research suggests that high-fiber diets may help improve mood and reduce anxiety and depression symptoms. Fermented foods, which contain beneficial bacteria, also show promise for mental health. The connection appears to work through changes in your gut bacteria—when you eat certain foods, it changes which bacteria thrive in your digestive system, and these bacteria may influence your brain and mood through various chemical signals.

The evidence for ketogenic diets (very low carbohydrate) is mixed, with some studies showing benefits for mood while others show no effect. Calorie-restricted diets also showed variable results. The research suggests that the type of diet matters less than whether it increases beneficial bacteria and reduces harmful ones.

Probiotics and prebiotic supplements showed conflicting results across studies. Some studies found they helped with anxiety and depression, while others found no benefit. This inconsistency may be because different probiotic supplements contain different types of bacteria, and what works for one person might not work for another.

The research highlights that the connection between gut bacteria and mood is bidirectional—meaning it works both ways. Not only does what you eat affect your bacteria and mood, but your mood and stress levels can also change your gut bacteria. This creates a cycle where stress can harm your gut health, which can worsen mood, which can further damage gut health. Breaking this cycle through dietary changes might help interrupt this negative pattern.

This review builds on growing evidence that the gut-brain connection is real and important for mental health. Previous research established that gut bacteria produce chemicals that affect the brain, but this review shows that dietary changes can harness this connection to potentially improve mental health. The findings align with increasing recognition in psychiatry that nutrition plays a role in mental health treatment.

The authors note several important limitations. Many studies reviewed were observational, meaning they can show that two things are connected but cannot prove that one causes the other. Different studies used different diets, different measures of anxiety and depression, and different populations, making it hard to compare results directly. Most research has been done in developed countries with specific populations, so results might not apply to everyone. The mechanisms explaining exactly how diet changes mood are still not fully understood. Finally, the authors emphasize that while dietary changes may help with mild anxiety and depression, they should not replace professional mental health treatment for moderate to severe conditions.

The Bottom Line

For people with mild anxiety or depression, trying dietary changes like increasing fiber intake and eating fermented foods may be worth attempting as a complementary approach (moderate confidence level based on current evidence). These changes are generally safe and have other health benefits. However, these dietary modifications should be combined with, not replace, professional mental health care. For moderate to severe anxiety or depression, speak with a mental health professional before relying on diet alone. Probiotic supplements show mixed evidence, so they are not recommended as a primary treatment at this time (low confidence level).

People with mild anxiety or depression who want to try non-medication approaches should care about this research. People interested in preventive mental health through nutrition should also find this relevant. However, people with severe depression or anxiety should prioritize professional mental health treatment. People with certain digestive conditions should consult their doctor before making major dietary changes.

Changes in gut bacteria can happen relatively quickly (within days to weeks of dietary changes), but improvements in mood and anxiety symptoms typically take longer to notice—usually several weeks to a few months. Don’t expect immediate results, but be patient as your body adjusts to new eating patterns.

Want to Apply This Research?

  • Track daily fiber intake (aim for 25-30 grams) and mood ratings on a scale of 1-10. Also note consumption of fermented foods like yogurt, sauerkraut, or kimchi. Track this for at least 4-8 weeks to see patterns between dietary changes and mood improvements
  • Start by adding one high-fiber food daily (like berries, beans, or whole grains) and one serving of fermented food daily (like plain yogurt or sauerkraut). Make these changes gradually to avoid digestive discomfort. Use the app to set reminders for these foods and track how you feel
  • Create a weekly mood check-in habit. Rate your anxiety and depression symptoms weekly using a simple scale. Compare these ratings to your dietary adherence over 4-week periods to identify patterns. Share this data with your healthcare provider to discuss whether dietary changes are helping

This review summarizes research on the relationship between diet and mental health, but it is not a substitute for professional medical or mental health care. If you are experiencing anxiety or depression, please consult with a qualified healthcare provider or mental health professional. Dietary changes should be made in consultation with your doctor, especially if you have existing health conditions or take medications. While dietary modifications may help with mild symptoms, moderate to severe anxiety and depression typically require professional treatment. Always speak with a healthcare provider before starting supplements or making significant dietary changes.