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Probiotic effects on brain function, as measured by resting state functional connectivity, persist 4-6 weeks after discontinuation in healthy older adults.

This RCT found that some brain-related effects of probiotics, particularly changes in resting state functional connectivity between the left superior parietal lobule and right occipital/cuneal/intracalcarine/supracalcarine cortex, persisted 4-6 weeks after cessation of a 6-week supplementation period. Additionally, significant time*group interaction effects were observed for Hospital Anxiety and Depression Scale Total Score and Anxiety Subscore between weeks 10-12 and week 6, but not from baseline. The study involved 32 healthy older adults (mean age 68.0 years) and compared two probiotic formulations of Lacticaseibacillus rhamnosus HN001 against placebo.

Last updated: Jul 31, 2026•1 RCTs•📖 Read as article →

Evidence Score

Evidence Score44/100
Human RCT★★☆☆☆
Meta-analysis☆☆☆☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. Probiotic effects on brain health are both transient and sustained for several weeks after discontinuation: a randomised controlled trial.

observational

Hutchinson AN, Brummer RJ, Rode J · Communications medicine (2026)

Participants: N/A
Duration: 6 weeks intervention + 4-6 weeks follow-up
Intervention: Daily supplementation with Lacticaseibacillus rhamnosus HN001 (encapsulated or non-encapsulated) for 6 weeks, followed by 4-6 weeks discontinuation.
Outcome: Resting state functional connectivity (seed-to-voxel analysis), Hospital Anxiety and Depression Scale (HADS) Total Score and Anxiety Subscore.
Effect Size: T = +7.38, cluster-size p = 0.0001 FDR-corrected (for connectivity analysis); time*group interaction effects reported for HADS scores but no specific effect size given.
Population: 32 community-dwelling self-reported healthy older adults (mean age 68.0 ± 5.4 years, 21 female/11 male) without contraindications for study examinations.

Result:

PubMed: 42521749DOI: 10.1038/s43856-026-01800-6

Mechanism Graph

Daily probiotic supplementation with Lacticaseibacillus rhamnosus HN001 modulates gut-brain axis
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Alters resting state functional connectivity patterns and anxiety symptom scores immediately post-intervention
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Some connectivity changes (e.g., left superior parietal lobule to occipital/cuneal cortex) persist 4-6 weeks after discontinuation
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Suggests longer-lasting gut-brain axis effects than previously presumed

Limitations

  • ⚠Small sample size (n=32 total, with uneven group sizes: 8, 12, 12 per group at follow-up)
  • ⚠Exploratory nature of outcomes (brain function as exploratory outcome of main study, psychological assessments as exploratory)
  • ⚠High attrition from randomization to analysis (e.g., 29 randomized to encapsulated group but only 8 analyzed)

Frequently Asked Questions

How long do probiotic effects on the brain last after stopping intake?▼

This study suggests some effects, particularly on resting state functional connectivity, persist for at least 4-6 weeks after discontinuation of a 6-week probiotic regimen.

What specific brain changes were observed with probiotics?▼

Significant differences in connectivity between the left superior parietal lobule and right occipital/cuneal/intracalcarine/supracalcarine cortex were found, along with changes in anxiety and depression scores.

Who was studied in this probiotic brain health trial?▼

The study included 32 community-dwelling healthy older adults with an average age of 68 years, mostly female (21 out of 32).

What type of probiotic was used in this study?▼

The probiotic used was Lacticaseibacillus rhamnosus HN001, tested in both encapsulated and non-encapsulated formulations.

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References

  1. 1.Hutchinson AN, Brummer RJ, Rode J. "Probiotic effects on brain health are both transient and sustained for several weeks after discontinuation: a randomised controlled trial.." Communications medicine, 2026. PMID: 42521749 DOI: 10.1038/s43856-026-01800-6
Disclaimer: This content is for educational purposes only and is not medical advice. Evidence scores reflect the quality and quantity of available research, not clinical recommendations. Always consult a healthcare professional before starting any supplement or intervention.