For some years now, scientific research has been paying growing attention to a two-way communication channel between the gut and the brain, called the “gut-brain axis”: an ongoing conversation carried through the vagus nerve, the immune system, and substances produced by the trillions of bacteria living in our intestines — the so-called microbiota. A review published in 2024 in the International Journal of Molecular Sciences, dedicated specifically to this axis in psychiatric disorders, summarizes the evidence linking the composition of the gut microbiota to mood, anxiety, and depression, opening the door to a new way of thinking about mental well-being: not just the head, but the gut too.
About 90% of the body’s serotonin is produced right in the gut, although that serotonin works mostly locally, regulating digestive motility, and doesn’t cross the blood-brain barrier directly to reach the brain. The link to mood is more indirect but just as concrete: gut bacteria produce substances (such as short-chain fatty acids) that communicate with the brain through the vagus nerve and modulate systemic inflammation, a factor increasingly associated with depression and anxiety. This is how the research field of “psychobiotics” was born: specific probiotic strains studied for a possible effect on mood — a field still young, but promising.
In practice, taking care of your microbiota means aiming for variety: different plant fibers (vegetables, legumes, whole grains) feed different bacterial strains, while fermented foods — yogurt, kefir, sauerkraut, kimchi — introduce useful live bacteria. But the axis works in both directions: chronic stress in turn alters the composition of the microbiota, potentially creating a vicious cycle. Taking care of your diet and taking care of your stress, from this angle, are two sides of the same coin for mental well-being.
Sources
- Mind, Mood and Microbiota — Gut-Brain Axis in Psychiatric Disorders (2024). International Journal of Molecular Sciences, 25(6).
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