Alzheimer's disease (AD) is one of the greatest health and social challenges of the 21st century. Due to the limited effectiveness of current pharmacotherapies, interest in diet and nutrition is growing. This article aims to critically review and synthesise the latest scientific research on the effectiveness of specific dietary approaches and key nutrients in preventing and treating AD. A literature review was conducted focusing on meta-analyses, randomised controlled trials (RCTs) and large prospective cohort studies from the PubMed, Scopus and Web of Science databases. Analysis of the evidence indicates that dietary patterns such as the Mediterranean diet (MeDi), the DASH diet and, in particular, the hybrid MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diet are strongly associated with a lower risk of AD and slower cognitive decline. The mechanisms underlying these benefits are multifaceted and include the reduction of oxidative stress and neuroinflammation, the improvement of vascular function and the modulation of amyloid-beta (Aβ) metabolism. Furthermore, recent studies provide evidence that molecules of microbial origin stimulate the immune response and directly participate in the aggregation of the Aβ peptide, as well as modulating the phenotype of glial cells. There is less clear evidence for the therapeutic potential of diet in people who have already been diagnosed, although the ketogenic diet shows promise. Dietary interventions based on holistic, plant- rich patterns appear to be a safe, cost-effective, evidence-based strategy for preventing AD. Further research is needed to establish its therapeutic role and develop personalised recommendations.