Author Identifier (ORCID)
Sithara Dissanayaka’s ORCID record 
Abstract
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that develops many years before clinical symptoms appear. The biological changes involved in the earliest stages remain poorly understood, particularly during the preclinical stage. Our previous work has identified gradual gut microbial and metabolic changes during this stage, suggesting these may represent early biological shifts that precede disease progression. Recent studies suggest that the gut microbiome may contribute to early AD processes through its effects on immune regulation, metabolism, and gut–brain communication. Changes in gut microbial composition, including reduced levels of short-chain fatty acid (SCFA)-producing bacteria, such as Faecalibacterium, Roseburia, and Eubacterium, have been reported in individuals with AD and mild cognitive impairment. These microbial alterations have also been linked to disrupted metabolic activity, impaired gut barrier function, and increased neuroinflammatory responses. Diet is an important factor influencing gut microbial composition and metabolic activity. Mediterranean, DASH, and prudent dietary patterns are generally associated with beneficial microbial profiles and increased SCFA production, whereas Western dietary patterns are linked to lower microbial diversity and increased pro-inflammatory taxa. This review summarises the current evidence linking gut microbiota, SCFAs, microbial metabolism, and dietary patterns with early AD pathology, while highlighting important gaps in the existing literature.
Keywords
Alzheimer’s disease, dietary patterns, gut microbiome, gut–brain axis, neuroinflammation, preclinical, short-chain fatty acids
Document Type
Journal Article
Date of Publication
8-1-2026
Article Number
2469
E-ISSN
20726643
Volume
18
Issue
15
PubMed ID
42588092
Publication Title
Nutrients
Publisher
MDPI
School
Centre of Excellence for Alzheimer's Disease Research and Care / School of Medical and Health Sciences
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Dissanayaka, D. M. S., Rainey-Smith, S. R., Sohrabi, H. R., Jayasinghe, T. N., Ho, V., Jayasena, V., Taddei, K., Masters, C. L., Martins, R. N., & Fernando, W. M. A. D. B. (2026). Gut microbiome changes in preclinical Alzheimer’s disease. Nutrients, 18(15). https://doi.org/10.3390/nu18152469