Fatty acid desaturase is a critical enzyme in PUFA metabolism, and genepolymorphism in FADS affects the activity and function of fatty aciddesaturase [50, 51], which in turn affects metabolic activities in the body, suchas lipid concentrations, cardiovascular disease risk, pregnancy, cognitivefunction, Alzheimer’s disease, overweight, and type 2 diabetes mellitus[20, 52, 53]. The gene discussed is SCD; the disease is early-onset autosomal dominant Alzheimer disease.