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Microbiota-gut-brain axis and probiotics: potential therapeutic strategies for treating Alzheimer's disease
Thekkuttuparambil Ananthanarayanan Ajith, Jagal Kishore Sreejith. Nutritional neuroscience, 2025-10-11
Topic: Gut, metabolism and diet
The gut-brain axis explains that changes in the intestinal microbiota influence Alzheimer's disease (AD). Short-chain fatty acids produced by the gut microbiome regulate the permeability of the gut and blood-brain barrier. Furthermore, they upregulate brain-derived neurotrophic factor, promote angiogenesis and neurogenesis, and control tau and Aβ proteins, microglial activity, apoptosis, oxidative damage, M1/M2 polarization of microglia, and neuroinflammation, which eventually improves cognitive impairment. This effect is mediated by modification of serotonin, dopamine, and γ-aminobutyric acid levels. Compared to healthy controls, mild cognitive impairment and AD were associated with low levels of Firmicutes and Bifidobacterium and high levels of Proteobacteria and Bacteroidetes. Lactobacillus and Bifidobacterium species were effective in improving cognitive function. More longitudinal research is needed to investigate precision medicine in patients with dysbiosis in the preclinical stages of the disease. This review describes the role of the gut microbiome and probiotics in AD.
Key findings
- Compared to healthy controls, mild cognitive impairment and AD were associated with low levels of Firmicutes and Bifidobacterium and high levels of Proteobacteria and Bacteroidetes.
Study details
- Study designlongitudinal study
- Evidence strengthModerate
How this study scored 61/100
Published in a peer-reviewed journal, and it is a longitudinal study following the same people over time. Scored zero for sample size, effect reported, studied in people and randomised / blinded because the record does not state it. We have no data on journal's citation record, times cited, citations per year, impact for its field and year, cited by studies here, still being cited, senior author's track record, institution's track record, multi-centre collaboration and free to read, so those were left out: it earned 34 of the 56 points we could judge it on, which is 61 out of 100.
| Component | Points | Why |
|---|---|---|
| Journal tier | 7 / 10 | Tier 3 — peer-reviewed journal (Nutritional neuroscience) |
| Journal's citation record | — / 4 | No journal record from OpenAlex — left out of this score |
| Study design | 7 / 12 | A longitudinal study following the same people over time |
| Strength of evidence | 3 / 5 | Rated “moderate” in our summary |
| Peer-review validation | 10 / 10 | Peer-reviewed. Published as an article in a named peer-reviewed journal. |
| How recent | 5 / 5 | 2026 — within 1 year(s) of the newest study here |
| Sample size | 0 / 4 | Participant count not stated — scores zero (not stated in the record — scored 0) |
| Effect reported | 0 / 3 | No effect size reported — scores zero (not stated in the record — scored 0) |
| Studied in people | 0 / 3 | Not stated whether this was studied in people — scores zero (not stated in the record — scored 0) |
| Randomised / blinded | 0 / 2 | No randomisation or blinding stated — scores zero (not stated in the record — scored 0) |
| Times cited | — / 7 | No citation count (not found in OpenAlex) — left out of this score |
| Citations per year | — / 5 | No citation count or no year — left out of this score |
| Impact for its field and year | — / 6 | No field-weighted citation impact (OpenAlex has none yet) — left out of this score |
| Cited by studies here | — / 6 | Not yet checked against this library's citation graph — left out of this score |
| Still being cited | — / 4 | No yearly citation counts — left out of this score |
| Senior author's track record | — / 4 | Senior author's record not available — left out of this score |
| Institution's track record | — / 3 | No institution listed in OpenAlex — left out of this score |
| Multi-centre collaboration | — / 3 | Institutions not listed — left out of this score |
| Indexed in PubMed | 2 / 2 | Indexed in PubMed (PMID 41074715) |
| Free to read | — / 2 | Access not recorded — left out of this score |
| Points | 34 / 56 | Scored on 10 of 20 parts. We have no data for the rest, so they are left out: 34 of the 56 points we could judge it on is 61 out of 100. |
| Total | 61 / 100 | — |
What each of these 20 components measures, and what this score is not →
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Cite this study APA, Vancouver, BibTeX · download .bib or .ris
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APA 7th
Ajith, T. A., & Sreejith, J. K. (2026). Microbiota-gut-brain axis and probiotics: potential therapeutic strategies for treating Alzheimer's disease. Nutritional neuroscience. https://doi.org/10.1080/1028415x.2025.2567429
Vancouver
Ajith TA, Sreejith JK. Microbiota-gut-brain axis and probiotics: potential therapeutic strategies for treating Alzheimer's disease. Nutritional neuroscience. 2026. doi:10.1080/1028415x.2025.2567429. PMID: 41074715.
BibTeX
@article{ajith2026-41074715,
author = {Ajith, Thekkuttuparambil Ananthanarayanan and Sreejith, Jagal Kishore},
title = {{Microbiota-gut-brain axis and probiotics: potential therapeutic strategies for treating Alzheimer's disease}},
journal = {Nutritional neuroscience},
year = {2026},
doi = {10.1080/1028415x.2025.2567429},
pmid = {41074715},
url = {https://doi.org/10.1080/1028415x.2025.2567429}
}
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