However, new research may provide insight into what those benefits are and when they run their course.
Writing in the journal Communications Medicine, researchers at Örebro University in Sweden used brain imaging to investigate the outcome of probiotic supplementation on healthy older adults.
“Our results indicate that some brain-related probiotic effects of just six-weeks of active intervention may be longer lasting than originally expected, highlighting their potential for mental well-being, here in an elderly population,” the researchers wrote. “These findings support the need to investigate the mechanisms underlying the persistent effects of probiotics on brain function.”
They added that some brain-related probiotic effects can continue four to six weeks post-intervention cessation, particularly brain function as indicated by resting state functional connectivity, or the spontaneous, low-frequency fluctuations in brain activity when a person is at rest and not performing a specific task.
An atypical assessment
Ongoing research into the gut-brain axis is revealing additional information about how aging and age-related diseases occur. More studies indicate that aging is associated with dysbiosis, or the imbalance in the microbial communities of the gut microbiota. This includes diminished bacterial diversity and the reduction of bacterial species that produce short-chain fatty acids.
The researchers describe probiotic supplementation as an emerging strategy to promote healthy aging, citing positive effects on immune function when healthy older adults take probiotic interventions. However, not many studies have explored probiotic interventions on brain health. Those that have typically used assessments like self-reported rating scales and paper-pencil tests to gauge efficacy.
In contrast, this study used magnetic resonance imaging (MRI), which can detect how probiotic interventions impact the resting state brain function.
“We found that a six-week intervention with encapsulated and non-encapsulated Lacticaseibacillus rhamnosus HN001 resulted in significant changes in brain connectivity as measured by resting state functional MRI (rsfMRI) in community-dwelling older adults (60 to 80 years),” the researchers explained. “Although increasing evidence suggests that probiotics affect brain health and function in healthy older adults, several unanswered questions remain.”
The scientists wrote that they questioned how long probiotics can impact brain health when the average range of a follow-up post discontinuation of supplementation is just one month. According to the researchers, only one other study has investigated brain imaging results after probiotic supplement cessation, but it followed up just 30 days after discontinuation.
Study details
The investigation was an exploratory follow-up of a six-week randomized, double-blind, placebo-controlled parallel study. Of the 90 participants randomized in the original trial, 32 completed the optional follow-up assessment four to six weeks after discontinuing supplementation.
The goal was to evaluate the continuous effects of a plant-based protein micro-encapsulated and non-encapsulated containing 6 × 10^9 CFU Lacticaseibacillus rhamnosus HN001 (provided by AnaBio Technologies) on functional connectivity assessed by resting state functional magnetic resonance imaging (rsfMRI).
The researchers explained that grey and white matter volume were evaluated along with psychological symptom ratings determined by self-administered questionnaires.
Participants were assessed at baseline and again after six weeks of probiotic supplementation. Supplementation was then discontinued, and participants underwent a follow-up assessment approximately four to six weeks later, at weeks 10 to 12, to determine whether any changes in brain function persisted after the intervention ended. The researchers observed mixed effects following supplementation cessation.
“A head-to-head comparison of both probiotic formulations for discontinuation follow-up versus baseline revealed non-significant differences in functional connectivity involving regions associated with language processing, attention, episodic memory, and spatial processing, while for discontinuation versus immediate intervention end significant functional connectivity differences were observed in regions associated with spatial perception, attention, visual processing, working memory,” the scientists wrote.
Perceived stress and sleep quality didn’t show meaningful group-specific effects, but HADS total and anxiety scores did show significant time × group effects, specifically in the encapsulated probiotic group. Those scores appeared to return toward baseline after discontinuation.
“While we demonstrate that some functional brain changes seem to persist for weeks after intake cessation, others are not detectable any longer,” the researchers noted. “Additionally, newly detected ones, so-called legacy effects, at discontinuation follow-up are observed.”
They also explained that the variations in effects could be attributed each formulation’s different mode of action as the encapsulated probiotic possibly reaches more distal regions of the gastrointestinal tract at higher ratios than the non-encapsulated one.
Source: Communications Medicine. doi: doi.org/10.1038/s43856-026-01800-6. “Probiotic effects on brain health are both transient and sustained for several weeks after discontinuation: a randomised controlled trial”. Authors: Ashley N. Hutchinson et al.
