Researchers in Japan studied how the bacteria living in mothers’ stomachs might be connected to depression and mood problems. They found that mothers with certain types of gut bacteria and eating habits had different levels of depression symptoms. Interestingly, mothers who ate more plant-based foods like soy, seaweed, mushrooms, and fermented foods seemed to have better moods and healthier gut bacteria. The study also showed that mothers with depression symptoms slept worse and felt more tired. This research suggests that what we eat and the tiny organisms in our digestive system might play a bigger role in mental health than we thought.

The Quick Take

  • What they studied: Whether the types of bacteria living in mothers’ digestive systems and their eating habits are connected to depression and mood problems
  • Who participated: Mothers in Japan who appeared healthy but were asked about their mood and depression symptoms. Researchers collected samples of their gut bacteria and asked about their diets
  • Key finding: Mothers with certain types of gut bacteria that produce a helpful substance called butyrate had higher depression symptoms. Mothers who ate more plant-based foods like soy, fermented foods, seaweed, and mushrooms had better moods and different gut bacteria
  • What it means for you: Eating more plant-based foods may help improve mood and mental health, especially for new mothers. However, this study shows a connection, not proof that diet causes better mood. Talk to your doctor before making major diet changes

The Research Details

This was a cross-sectional study, which means researchers looked at a group of mothers at one point in time and collected information about their mood, diet, and gut bacteria all at once. They used a special lab test called 16S rRNA gene sequencing to identify exactly which types of bacteria were living in each mother’s digestive system. They also asked mothers questions about their sleep quality, physical health, and what they typically eat. This type of study is good for finding connections between things, but it can’t prove that one thing causes another.

This research approach is important because it looks at real mothers in their normal lives rather than in a lab setting. By studying mothers in Japan specifically, the researchers could see how cultural eating habits and attitudes toward mental health affect depression. The study also combined three important areas—mental health, gut bacteria, and diet—which doctors don’t always look at together

This study was published in a respected scientific journal (PNAS nexus), which means it went through expert review. However, because it’s a cross-sectional study, we can only see that certain factors are connected to depression, not that they cause it. The study focused on Japanese mothers, so results might be different in other countries with different diets and cultures. The exact number of mothers studied wasn’t provided in the information given

What the Results Show

The researchers discovered that mothers with higher diversity of gut bacteria and more of certain bacteria types (like Lachnospira, Faecalibacterium, and Subdoligranulum) actually reported higher levels of depression symptoms. This was surprising because scientists often think more diverse bacteria is better. Mothers who had these bacteria patterns also reported worse sleep quality and felt more physically tired and unwell. The study suggests that it’s not just about having lots of different bacteria, but about having the right balance of bacteria types. Additionally, mothers who ate diets rich in plant-based foods—especially soy products, fermented foods like miso and kimchi, seaweed, mushrooms, and vegetables—showed lower depression symptoms and had different, potentially healthier bacteria patterns in their guts.

The research found that sleep quality was noticeably worse in mothers with higher depression symptoms, and these mothers also reported more physical health problems overall. The connection between diet and gut bacteria was clear: mothers eating more plant-based foods had different types of bacteria that may be more beneficial. The study also noted that many Japanese mothers don’t seek help for depression because of cultural attitudes about mental health, which means depression in mothers might be more common than doctors realize

Previous research in Western countries has shown connections between gut bacteria and depression, but this is one of the first studies to look specifically at mothers who appear healthy but may have hidden depression. Most earlier studies focused on people with diagnosed depression disorders, not mothers in the general population. This study adds important information by showing that even healthy-seeming mothers can have depression symptoms that connect to their gut bacteria and diet

This study only looked at mothers at one point in time, so we can’t know if the gut bacteria caused the depression or if depression caused changes in the bacteria. The study was done only in Japan, so the results might not apply to mothers in other countries with different diets and cultures. We don’t know exactly how many mothers were studied from the information provided. The study relied on mothers reporting their own symptoms, which might not be completely accurate. Finally, this study shows connections between things but doesn’t prove that changing your diet will definitely improve depression

The Bottom Line

Based on this research, mothers may benefit from eating more plant-based foods including soy products, fermented foods, seaweed, mushrooms, and vegetables. These foods appear to support healthier gut bacteria and may be connected to better mood. However, this is not a proven treatment for depression. If you’re experiencing depression symptoms, talk to your doctor or mental health professional. Diet changes alone should not replace professional mental health care. Consider gradually adding more plant-based foods to your diet while also seeking appropriate medical support

This research is most relevant to mothers, especially those in the postpartum period or those experiencing mood changes. It’s also important for doctors and healthcare providers who care for mothers. Anyone interested in how diet affects mental health should find this interesting. However, if you have diagnosed depression, don’t rely only on diet changes—work with a mental health professional

Changes in gut bacteria from diet changes typically take several weeks to a few months to become noticeable. Mood improvements from dietary changes would likely take a similar timeframe, though this varies by person. Don’t expect immediate results; think of this as a long-term approach to supporting your mental health

Want to Apply This Research?

  • Track daily intake of plant-based foods (servings of soy products, fermented foods, seaweed, mushrooms, and vegetables) and rate your mood and sleep quality each evening on a simple 1-10 scale. Look for patterns over 4-8 weeks
  • Start by adding one plant-based food category to your diet each week. Week 1: add fermented foods like miso soup or yogurt. Week 2: add seaweed or mushrooms. Week 3: add more soy products. Week 4: increase vegetable variety. Use the app to log these additions and track how you feel
  • Create a weekly mood and sleep quality summary in the app. Also track which plant-based foods you ate most that week. Over 2-3 months, review trends to see if weeks with more plant-based foods correlate with better mood and sleep. Share this data with your healthcare provider

This research shows a connection between gut bacteria, diet, and depression symptoms, but does not prove that diet changes will treat or cure depression. If you are experiencing depression, anxiety, or other mental health concerns, please consult with a qualified healthcare provider or mental health professional. Do not use dietary changes as a replacement for professional mental health treatment. This information is for educational purposes only and should not be considered medical advice. Always discuss any significant dietary changes with your doctor, especially if you are pregnant, breastfeeding, or taking medications.