ABSTRACT
Fatty acids control the structure and function of biological membranes, including membranes in the nervous system. The brain has higher lipid content than any other of the body’s organs, except adipose tissue itself. All its lipids, which are mostly phospholipids, are found in cell membranes, and they are almost never sources of energy. Position 2 of the glycerol molecules in phospholipids generally bears a polyunsaturated fatty acid such as docosahexanoic acid (DHA; 22:6(n-3), 22:6ω3, cervonic acid), or arachidonic acid (ARA; 20:4(n-6), 20:4ω6). There may well be smaller amounts of adrenic acid (22:4ω6) and eicosapentanoic acid (EPA; 20:5(n-3), 20:5ω3) or docosapentaenoic acid (22:5ω3). The brain contains very little alpha-linolenic acid (ALA; 18:3(n-3), 18:3ω3) although this fatty acid is the precursor of all the other omega-3 fatty acids. The families of fatty acids are shown in Figure 39.1. A major component of brain membrane phospholipids is the omega-3 fatty acid DHA, and high concentrations of this fatty acid are found in the more metabolically active area of the brain, including the frontal cerebral cortex, which is involved in cognition, mitochondria, nerve endings, and synaptic vesicles. Most studies on cognition have focused on omega-3 fatty acids, or the
I. Introduction .......................................................................................................................... 935 II. Brain Development: Evidence from Animal Models and Studies on Humans .................... 937 A. Experimental Evidence ................................................................................................... 937 B. EPA and DHA in Human Baby Formulas ...................................................................... 939 C. Importance of the Balance between Omega-6 and Omega-3 Fatty Acids ...................... 939 III. Adult Humans, Epidemiological and Experimental Evidence ............................................. 940 A. Mental Health, Cognition, and Mood ............................................................................. 940 B. Stress ............................................................................................................................... 941 C. Hyperactive and Dyslexic Children, Dyslexia in Adult .................................................. 941 D. Depression ...................................................................................................................... 942 E. Drug Addiction ............................................................................................................... 943 F. Autism ............................................................................................................................ 943 G. Dementias ....................................................................................................................... 943 H. Schizophrenia ................................................................................................................. 944 I. Cognition and Aging ....................................................................................................... 945 IV. Discussion ............................................................................................................................. 946 V. Summary and Conclusions ................................................................................................... 947 References ................................................................................................................................... 948
balance between these fatty acids and omega-6 fatty acids. However, one review has examined the role of the ARA cascade in affective disorders (Sublette and Trappler, 2000).
