Eating for two

Kyoto, Japan -- Giving birth is hard enough; postpartum depression can make adjusting to parenthood all the more difficult. A healthy diet is essential for new mothers to build strength after such a taxing ordeal, but what if what they eat could also lower the risk of baby blues?

While studies in Western countries have linked gut microbiota to depressive symptoms, little is known about this association in healthy postpartum mothers, particularly in Japan, where cultural barriers often prevent mothers from seeking psychiatric help.

This inspired a team of researchers at Kyoto University to design a cross-sectional study of 344 women from across Japan raising young children. The team assessed participants' depressive and physical symptoms as well as their dietary habits, and analyzed their stool samples.

"Our investigation was driven by the need to better understand how intestinal microbiota, physical condition, and dietary habits relate to maternal mood, even among mothers not clinically diagnosed with mental illness," says first author Michiko Matsunaga.

The results indicated that microbiome diversity and relative abundance of butyrate-producing bacteria were associated with high levels of depressive mood. On the other hand, a diet rich in fermented foods, soy products, mushrooms, and seaweed -- typical of Japanese cuisine -- may help regulate the gut environment and contribute to preventing depression.

The team expected that a typical "healthy diet" based on a balanced intake of vegetables, fish, and meat would demonstrate the best results, but traditional Japanese foods were even more strongly associated with improved gut microbiota and reduced depressive symptoms.

"These findings deepened our appreciation for the richness of traditional Japanese dietary culture and its potential mental health benefits," says team leader Masako Myowa. The results also contribute to a growing body of research supporting the gut–brain axis, adding evidence from a Japanese context, which has been underrepresented in microbiota studies.

This study points to the potential value of non-pharmacological support through diet and lifestyle, especially for postpartum women who may benefit most from low-barrier interventions before relying on medication. It also highlights the need to assess depressive symptoms in postpartum mothers even in non-clinical populations, as approximately 14% of healthy mothers showed signs of severe depression.

However, further research is required to solidify these associations. The dietary data were based on self-reported questionnaires, which are subject to recall bias and individual perception. This study represents only the first step in exploring the relationship between gut microbiota, depressive symptoms, and dietary habits in postpartum women.

Ultimately, the research team hopes to implement intervention studies based on this data to examine whether targeted dietary changes can improve both gut microbiota and mental health in postpartum populations.

"I find it fascinating that this integrated perspective may help us better understand emotional states and develop new, holistic approaches to mental health support," says Matsunaga.

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The paper "Association of short-chain fatty acid–producing gut microbiota and dietary habits with maternal depression in a subclinical population" appeared on 2 September 2025 in PNAS nexus, with doi: 10.1093/pnasnexus/pgaf169

About Kyoto University

Kyoto University is one of Japan and Asia's premier research institutions, founded in 1897 and responsible for producing numerous Nobel laureates and winners of other prestigious international prizes. A broad curriculum across the arts and sciences at undergraduate and graduate levels complements several research centers, facilities, and offices around Japan and the world. For more information, please see: http://www.kyoto-u.ac.jp/en