DHA is shown to influence brain development through the effects on gene expression, monoaminergic neurotransmission, or protection against apoptotic cell death. Thus, DHA enhanced neurite outgrowth of hippocampus and cortical neurons and clonal pheochromocytoma (PC12). In experimental animals, diets deficient in omega-3 PUFA resulted in decreased cell size of neurons in the hippocampus, hypothalamus, and parietal cortex and substantial disturbances in neural function. In aged mice, supplementation with high DHA significantly lowered β-amyloid content by around 70% with a decrease in the levels of β-amyloid protein 42 (βAP42). Dietary supplementation with DHA partly protected from overexpression of NMDA receptor subunits but fully prevented CaMKII decrease in transgenic mice. The DHA levels were found to be low in the serum and the brains of Alzheimer’s disease (AD) patients and the levels of total and phosphorylated Tau protein in CSF were high; supplementation with DHA decreased these levels suggesting neuroprotective action. In conclusion, supplementation with DHA may be safe for prophylactic, if not therapeutic application in AD.