Docosahexaenoic acid (DHA, C22:6, ω-3) is a highly polyunsaturated
omega-3 fatty acid. It is concentrated in neuronal brain membranes, for which reason it is also referred to as a "brain food". DHA is essential for brain development and function. It plays an important role in improving
antioxidant and cognitive activities of the brain. DHA deficiency occurs during aging and
dementia, impairs memory and learning, and promotes age-related
neurodegenerative diseases, including
Alzheimer's disease (AD). For about two decades, we have reported that
oral administration of DHA increases spatial memory acquisition, stimulates neurogenesis, and protects against and reverses memory impairment in
amyloid β
peptide-infused AD rat models by decreasing amyloidogenesis and protects against age-related
cognitive decline in the elderly. These results demonstrate a robust link between DHA and cognitive health. Rodents that were fed a diet low in ω-3
polyunsaturated fatty acids, particularly those that were DHA-deficient, frequently suffered from anxiety, depression and memory impairment. Although the exact mechanisms of action of DHA in brain functions are still elusive, a host of mechanisms have been proposed. For example, DHA, which inherently has a characteristic three-dimensional structure, increases membrane fluidity, strengthens
antioxidant activity and enhances the expression of several
proteins that act as substrates for improving memory functions. It reduces the brain
amyloid burden and inhibits in vitro fibrillation and
amyloid-induced neurotoxicity in cell-culture model. In this review, we discuss how DHA acts as a molecule with diverse functions.