Exploring the gut-brain axis: dietary influences on Alzheimer's disease pathogenesis

Alzheimer's disease (AD) is one of the most diagnosed neurodegenerative disorders worldwide and presents a significant challenge for both affected individuals and their caregivers. Alzheimer's disease is characterized by the accumulation of amyloid plaques and dysfunctional tau protein in the brain, along with the final development of dementia. Recently, in addition to the strongly developing ischemic etiology of AD, it is suggested that the gut and oral microbiota may also participate in the development of this disease. This involvement may stem from an unbalanced diet and the consumption of foods containing harmful chemical additives. An unhealthy diet can compromise the integrity of the gut barrier, facilitating the translocation of bacterial pathogens and leading to a pro-inflammatory T-cell response mediated by innate immune cells. This inflammatory response can disrupt systemic homeostasis and may contribute to neuroinflammation. The brain and gut interact through a complex network known as the "gut-brain-microbiota axis," and emerging studies suggest that the intestinal microbiota and their metabolites may play a significant role in the pathogenesis of Alzheimer's disease. Moreover, these inflammatory mediators and microbial metabolites can reach the brain via the gut-brain axis, potentially exacerbating neurodegenerative processes. Preclinical and limited clinical evidence indicates that low-fiber diets are associated with alterations in intestinal microbiota composition, which may contribute to the onset and progression of Alzheimer's disease. This review aims to explore the potential connections between AD and the gut microbiome, emphasizing the significance of dietary factors in shaping these relationships. A comprehensive understanding of the interactions between the human microbiome and the brain, particularly in the context of diet and its ingredients, may enhance our understanding of AD etiology and inform the development of preventative strategies, through dietary modifications or therapeutic interventions. This area of research holds promise for identifying novel approaches to prevent or slow the progression of AD.