Omega 3 polyunsaturated fatty acids and cognitive function

The two essential fatty acids, linoleic and a-linolenic acid, are the starting point for the synthesis of two different series of polyunsaturated fatty acids (PUFAs) named n-6 and n-3, respectively,. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are considered the most important n-3 fatty acids from a physiological and functional point of view. Although no specific neuronal process had been unambiguously identified to explain the effects of PUFAs on neuronal function or cognition, many studies suggest that PUFAs are essential for normal brain development and function. DHA is an absolute requirement for tbe development of the human centrai nervous system (CNS), and its concentration in CNS synapses and in retinal photoreceptors is extremely high. DHA incorporated predominant1y into the sn-2 position of membrane phospholipids acts within the membrane in signal transduction, neurotransmission, and formation of lipid rafts. Unesterified DHA may be enzymatical1y oxygenated to generate neuroprotectin DI, which in turn elicits potent neuroprotective functions. DHA is also a primary lipid peroxidation target during periods of excessive oxidative stress, and may be oxidized non enzymatical1y into neuroprostanes. However, some reports have concluded that DHA or fish oil supplementation resulted in anti-oxidant effects. 0>-3 PUFAs have been also shown to regulate many genes, and this direct effect might be one of the clues to understand their beneficiaI effects on the nervous system. Tbe level of DHA seems to be cTUcial for normal cognitive function, and several epidemiological and experimental studies suggest that an increased DHA dietary intake could provide a substantial protection in CNS. DHA supplementation undoubtedly represents one of the most promising preventive approaches to any alteration in cognitive function and tbe onset of dementia.