Microbiota-Brain Interactions in Dementia: Role of Diet in Neuroinflammation

Aging is one of the risk factors for dementia, a group of neurocognitive disorders characterized by a progressive decline in cognitive function. Alzheimer's disease (AD) is the most prevalent, followed by vascular dementia (VaD). Other subtypes, such as frontotemporal dementia (FTD) and Lewy body disease (LBD), are less common but exhibit distinctive symptoms related to motor deficits, behavioral changes, and neuropsychiatric disturbances. Each type of dementia is associated with specific pathological features, such as amyloid plaques in AD and tau tangles in FTD. Recent research highlights the significant role of gut microbiota in the pathogenesis of dementia. Gut dysbiosis, or an imbalance in the gut microbiota, has been linked to neuroinflammation, cognitive decline, and neurodegenerative diseases through the gut-brain axis (GBA). Key microbial species, such as Bacteroides and Firmicutes, produce metabolites that influence neuroinflammation, immune response, and the integrity of the blood-brain barrier (BBB). Short-chain fatty acids (SCFAs), such as butyrate, have anti-inflammatory effects, while tryptophan derivatives, such as indole-3-acetic acid (IAA), support intestinal barrier function and modulate neuroinflammatory pathways. Microbial-derived metabolites may serve as potential therapeutic targets to mitigate neurodegeneration, highlighting the intricate relationship between the gut microbiota and brain health. Dietary interventions, such as a balanced diet rich in fiber, antioxidants, and anti-inflammatory compounds, may help support gut health by promoting a balanced gut microbiota and reducing the risk of developing dementia. This review highlights the relationship between brain function, gut microbiota composition, and dementia, providing insights into potential dietary strategies for prevention and management.