NA is the source of sphingomyelins in the nervous system and is used to form the myelin sheath membranes (Babin et al., 1993; Peters et al., 2013).

NA is a structure component of the white matter of brain, which can be used in vivo as raw materials for repairing outer membranes of nerve fibers, and the synthesis of ganglioside, cerebroside ester and sphingomyelin (Sargent et al., 1994 ; Amminger et al.,2012).

The deficiency of NA can cause structural damage to the whole brain and is the main cause of degenerative brain diseases (Babin et al., 1993; Peters et al., 2013).

NA is one of the major fatty acids in brain sphingolipids, normally accounting for approximately 40% of the total fatty acids in sphingolipids. ARA, DHA and NA are three major structural functional compounds in the nervous system.