Some studies have highlighted how prebiotics can reduce AD symptoms by improving good microbiota and probiotics by reinforcing the gut barrier function [64]; on the other hand, an increase of dietary and metabolic factors that can elicit a higher response of Th17 cells and their cytokines (IL-17, IL-22) may determine cognitive impairment, even in the absence of amyloid plaques [65]. This evidence concerns the gene IL17A and Alzheimer disease.