Abstract
Introduction: In the context of neurodegenerative diseases, Alzheimer's disease (AD) is the most common form of dementia. It is estimated that more than 46 million people are affected worldwide. Several factors contribute to the risk of developing late-onset Alzheimer's disease, including advanced age, genetic factors, family history, history of head trauma, hypertension in midlife, obesity, diabetes, and hypercholesterolemia. Studies have shown the important role of the gut microbiota in controlling this condition, together with adequate nutrition. Objective: It was to analyze the relationship between dietary patterns, gut microbiota, micro and macronutrients, and cognitive disorders in Alzheimer's disease. Methods: The systematic review rules of the PRISMA Platform were followed. The search was conducted from May to August 2024 in the Scopus, PubMed, Science Direct, Scielo, and Google Scholar databases. The quality of the studies was based on the GRADE instrument and the risk of bias was analyzed according to the Cochrane instrument. Results and Conclusion: A total of 140 articles were found. 75 articles were fully assessed and 30 were included and developed in the present systematic review study. Considering the Cochrane tool for risk of bias, the overall assessment resulted in 15 studies with a high risk of bias and 25 studies that did not meet GRADE and AMSTAR-2. Most studies showed homogeneity in their results, with X2=89.5%>50%. It was concluded that several antioxidants found in a healthy natural diet can efficiently attenuate free radical attacks and neutralize dysregulated pro-oxidants, reducing oxidative stress and the induction of degenerative diseases such as Alzheimer's disease. Studies have found that plasma lipopolysaccharide levels in patients with Alzheimer's disease were three times higher than in healthy controls. Thus, increased concentrations of plasma lipopolysaccharide and fecal calprotectin indicate an altered intestinal barrier function and increased inflammation and intestinal permeability in patients with Alzheimer's disease.