Visual and brain in studies of n-3 of infants function measurements fatty acid requirements Ricardo Uauy, MD, PhD, Eileen Birch, PhD, David Birch, PhD, and Patricio Peirano, MD From the Developmental Neurophysiology and Clinical Nutrition Units, institute of Nutrition and Food Technology University of Chile, Santiago, Chile, and the Retina Foundation of the South- west, Dallas, Texas Dietary n-6 or n-3 fatty acid deficiencies result in changes in brain and retinal phospholipid composition that can affect cell membrane and organ function. An n-3 fatty acid deficiency has been associated with altered electroretino- grams and reduced visual acuity in animals. Other promising methods for assessing the effects of fatty acid deficiencies on brain and retinal maturation include visual-evoked potential acuity, sleep-wake cycle, auditory brain stem- evoked response, somatosensory-evoked potential measurements, and the Fagan and forced-choice preferential looking acuity tests. Preterm infants fed a formula low in =-linolenic acid (18:3n-3) had significant electroretinographic changes at discharge from the nursery, indicating a delay in rod photoreceptor maturation. However, infants fed human milk or supplementary n-3 fatty acids as marine oil had electroretinogram indexes like those of infants of compara- ble age tested soon after birth. Visual cortex function, measured by pattern re- versal visual-evoked potential and forced-choice preferential looking visual acuity response, was also better in infants fed human milk or marine oil-supple- mented formula than in infants fed formulas without docosahexaenoic acid (22:6n-3). Studies of term infants suggest that visual acuity is more mature in for- mula-fed relative to breast-fed infants at 4 months and 3 years of age. (J PEDIATR 1992;120:$168"80) Recently the effects of dietary fats and n-3 fatty acid sup- plementation on brain and eye function have been the focus of extensive research. Dietary fat composition in early life can affect the developing nervous system by at least three potential mechanisms. First, dietary n-6 and n-3 fatty acids can directly modify the structural composition of brain tis- sues and photoreceptor membranes. Second, the availabil- ity of eicosanoids and the recently discovered docosanoids, which are endogenous mediators derived from n-3 and n-6 fatty acids, can indirectly affect the nervous system. These compounds have important roles in the response of neural tissues to various physiologic stimuli. Third, the metabolic Supported by National Institutes of Health grants HD 22380, EY 05235, and EY 05236 and Fondecyt grant 1066-91. Reprint requests: Ricardo Uauy, MD, PhD, Institute of Nutrition INTA, University of Chile, Casilla 138-11, Santiago, Chile. 9/0/36820 effects of dietary fat as an oxidative fuel or its effects on the hormonal milieu can mediate its effects on function. This review addresses primarily the effects of n-3 fatty ABER CNS DHA EPA FPL MCT PUFA RBC TPN VEP Auditory brain stem-evoked response Central nervous system Docosahexaenoic acid (22:6n-3) Eicosapentaenoic acid (20:5n-3) Forced-choice preferential looking Medium-chain triglycerides Polyunsaturated fatty acid Red blood cell Total parenteral nutrition Visual-evoked potential acids on central nervous system function. The effects of other nutrients, including n-6 fatty acids, will als0 be included to illustrate potential new methods that evaluate the effects of diet on brain and visual function. This anal- S168