However, also effects of other environmental toxins on gut microbiota and on mental health should be investigated in more detail: recent reviews depict that neurotoxic metals such as lead, mercury, aluminum, cadmium and arsenic, as well as some pesticides and metal-based nanoparticles (NP) are involved in AD pathogenesis, as they are able to increase Aβ peptide and the phosphorylation of Tau protein (P-Tau), causing amyloid plaques and neurofibrillary tangles characteristic of AD [253,254]. This evidence concerns the gene MAPT and Alzheimer disease.