Newer reviews keep mapping the microbiota‑gut‑brain axis, including fermented foods as a whole‑food approach to modulating the microbiome. Separately, large meta‑analytic work links higher fiber intake with better mental health outcomes in observational data (causality still being tested).
Try this: add 1 fiber‑rich food/day for 2 weeks, then 2/day. Add fermented foods slowly if you’re sensitive.