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The fatty acid compositions of the major cerebral cortex phospholipids, phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine were measured in 16 term and one preterm 'cot death' infants fed exclusively either breast milk or one of two formulas. Docosahexaenoic acid (DHA; C22:6n-3) content in cerebral cortex phosphatidylethanolamine and phosphatidylserine of breast fed infants was greater than in both formula groups with significances varying between p<001 and p<0001. Compensation for this deficiency in DHA in the formula fed infants was largely achieved by increased incorporation of docosapentaenoic acid (C22:5n-6) in the cerebral cortex of term infants and Mead (C20:3n-9) and dihomo Mead acids (C22:3n-9) in the preterm infant.As the phospholipids most affected are known to perform an important role in membrane fimction and are possibly integral to neurotransmission it is recommended that breast milk substitute infant formulas should contain n-3 and n-6 series polyunsaturated fatty acids in proportions similar to those ofhuman milk. (Arch Dis Child 1995; 72: 198-203) Approximately 60% of the total energy intake of the infant during the first year is utilised by the brain and much of this energy is used to synthesise neuronal membrane and deposit myelin. Fatty acids from human milk or infant formulas provide not only a source of hydrocarbon for energy production but help synthesise the complex hydrocarbon structures necessary for the creation of neurotransmitter membranes.Breast fed infants have significantly greater concentrations of the long chain polyunsaturated fatty acid (PUFA), docosahexaenoic acid (DHA; C22:6n-3) in their cerebral cortex phospholipids than infants fed current infant formulas.2 3 Cerebral cortex neuronal membrane phospholipids are composed of phosphatidylcholine, phophatidylethanolamine, phosphatidylserine, and phosphatidylinositol. While the membrane receptor and secondary messenger characteristics of phosphatidylinositol and its meta-

There is little evidence as to the fatty acid composition of the cerebellum in infancy and it remains uncertain whether milk diet can influence its composition. We therefore examined cerebellar gray and white matter of infants less than 6 month old who had died unexpectedly. The fatty acid content of 33 gray and 21 white matter specimens from infants born at term and 6 gray and 5 white matter specimens from preterm infants was assessed by gas chromatographic/mass spectrometric analysis. Infants were grouped according to whether they had received human or manufactured formula milk. Whereas cerebellar cortex docosahexaenoic acid (DHA, 22:6n-3) concentrations were significantly lower (P<0.01) in the formula-fed than breast-fed infants, no differences existed between the term (n = 10) and preterm (n = 5) Synthetic Milk Adapted [corrected] (SMA) formula-fed infants. Cerebellar white matter DHA concentrations were similarly lower (P<0.01) in the SMA formula-fed infants (n = 8) than in an age-matched breast-fed group. Low concentrations of cerebellar white matter lignoceric (24:0) and nervonic acid (24:1n-9) in two 7-wk-old preterm infants appeared to correlate with postgestational rather than chronological age. Dietary long-chain polyunsaturated fatty acids, particularly DHA, are probably essential for normal development of the infant cerebellum.

Having demonstrated a deficiency in infant cerebral cortex docosahexaenoic acid of formula fed compared with breast milk fed infants, we sought to identify why the extensive subcutaneous tissue triglyceride fatty acid reserves in term newborn infants appeared to be ineffectual in its prevention.In addition to 24 term and six preterm infants who died from 'cot death', tissue was analysed from four perinatal surgical patients and in the former the results were correlated with dietary milk intake. The higher amounts (about 15% by weight) of unsaturated linoleic acid supplied in the formula milks were quantitatively incorporated into the subcutaneous tissue largely at the expense of the saturated palmitic acid possibly compromising adipocyte fluidity. The six preterm infants were in two formula fed groups and there was only one significant difference, namely a higher subcutaneous tissue concentration of o-linolenic acid in one of the preterm groups, distinguishing them from their term counterparts. This may imply that the enzymes involved in absorption and digestion of fatty acids are mature in the preterm infant. From birth the mean weight percentage of docosahexaenoic acid (0.4Gb) fell rapidly to undetectable levels (<0-05Gb) in the formula fed group after about two months. It is therefore concluded that if breast feeding is not possible then a minimum daily requirement of a-Linolenic acid (C 1 8:3n-3)

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