In the context of AD, vitamin D affects the formation of beta-amyloid plaques and has a protective effect against neuroinflammation and its deficiency is associated with an increased risk of dementia and Alzheimer’s disease as neuroinflammation status, by leading to dysbiosis of the gut microbiota and to the consequent release of leptin and adiponectin, causes a reduction in the absorption of vitamin D and its precursors with consequent change in the density of bone [37]. The gene discussed is LEP; the disease is Alzheimer disease.