What question did this study set out to answer?

This trial aims to assess the effects of probiotics on biological markers in older adults with mild cognitive impairment and Alzheimer's disease.

July 4, 2026Open Access

Effect of Probiotic Supplementation in Older Individuals with Mild Cognitive Impairment and Alzheimer’s Disease: A Randomized, Placebo-Controlled, Triple-Blind Clinical Trial

EMEduarda Behenck MedeirosD’Or Institute for Research and Education IMIsadora de Oliveira MonteiroUniversidade do Extremo Sul Catarinense BKBruno Kluwe‐SchiavonUniversity of Lisbon

Key Points

This trial aims to assess the effects of probiotics on biological markers in older adults with mild cognitive impairment and Alzheimer's disease.
Randomized, triple-blind, placebo-controlled clinical trial with older adults classified as cognitively unimpaired, MCI, or AD.
Participants received a probiotic blend for 12 weeks, with assessments of DNA damage, inflammatory cytokines, and neurotrophic factors.
Study examined changes in stool consistency before and after intervention.
No significant increase in alkaline or oxidative DNA damage was observed, confirming the safety from genotoxicity.
Changes in inflammatory and neurotrophic biomarkers were primarily influenced by time and participant subgroup, not by treatment.
An exploratory increase in NGF levels was noted in the MCI probiotic group, but other changes across the biomarker panel were inconsistent.

Abstract

Alzheimer's disease (AD) is the most common type of dementia in older adults and often precedes mild cognitive impairment (MCI). These conditions are associated with biological alterations involving chronic inflammation, neuronal dysfunction, and genomic instability. In parallel, growing evidence has suggested a role for the gut-brain axis in cognitive aging, and probiotics have been investigated as a potential strategy to modulate inflammatory and neurotrophic pathways. This randomized, triple-blind, placebo-controlled clinical trial evaluated the effects of 12 weeks of supplementation with a probiotic blend containing Lactobacillus and Bifidobacterium strains in older adults classified as cognitively unimpaired (CU), MCI, or AD. The study examined DNA damage, inflammatory cytokines, neurotrophic factors, and stool consistency before and after the intervention. Overall, probiotic supplementation showed limited and heterogeneous effects across outcomes. DNA damage analyses did not indicate increased alkaline or oxidative DNA damage after probiotic supplementation, supporting the absence of detectable genotoxicity over the intervention period. Changes in inflammatory and neurotrophic biomarkers were more strongly related to time and diagnostic subgroups than to treatment allocation. Exploratory findings suggested a possible subgroup-specific effect on neurotrophic markers, particularly an increase in NGF in the MCI probiotic arm, but this pattern was not consistent across the broader biomarker panel. Stool consistency did not show reliable pre- to post-intervention changes. These findings suggest that the probiotic formulation was safe from a genotoxic perspective but did not produce a generalized biological effect across inflammatory, neurotrophic, or gastrointestinal outcomes. Larger studies incorporating dietary monitoring and microbiota profiling are needed to clarify whether specific probiotic strains can influence biological pathways relevant to cognitive aging.

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