Tissue levels of polyunsaturated fatty acids during early human development

Arachidonic acid offsets the effects on mouse brain and behavior of a diet with a low (n-6):(n-3) ratio and very high levels of docosahexaenoic acid

This study investigated the effects of varying dietary levels of very long-chain polyunsaturated fatty acids on growth, brain fatty acid composition and behavior in mice. Five groups of pregnant and lactating B6D2F1 mice were fed diets with either a very high (n-6):(n-3) ratio of 49 [(n-3) deficient)], a normal ratio of 4.0 or a low ratio of 0.32. The (n-6) fatty acids (FA) were provided either entirely as linoleic acid (LA) or as LA in combination with arachidonic acid (ARA), and the (n-6):(n-3) ratios were adjusted by partial replacement of the (n-6) FA with docosahexaenoic acid (DHA). Offspring were maintained on these diets after weaning. The diets with the low (n-6): (n-3) ratio had no effect on the birth weights of the pups, but after 15 d resulted in a significant 12% reduction in body weights. This effect persisted to adulthood and was apparent in both brain and body weights unless ARA was substituted partially for LA as the source of (n-6) FA. There were significant effects of diet on brain fatty acid composition. Increasing levels of DHA in the diet increased brain DHA and decreased ARA, and there was also retroconversion of DHA in EPA in the mice fed high levels of DHA. Addition of ARA to the diet increased brain ARA, and, at high levels only, decreased DHA. There were no effects of this wide variation in dietary (n-6):(n-3) ratio on the ability of the mice to learn the place of the hidden platform in the Morris water maze. However, in both the cued and the place learning, the mice fed the low (n-6):(n-3) diet swam more slowly, unless ARA substituted partially for LA as the source of (n-6) FA. There were no effects of diet on activity in the spatial open field. These findings show that the effects of a diet with a low (n-6):(n-3) ratio and (n-3) FA provided as DHA, can be overcome if LA is partially replaced by ARA as the source of (n-6) FA.

Increasing dietary linoleic acid in young rats increases and then decreases docosahexaenoic acid in retina but not in brain

The accumulation of fatty acids in retina, brain, liver, and plasma of 30-day-old rat pups consuming various levels of linoleic acid (LA, 18:2n-6) and constant alpha-linolenic acid (ALA, 18:3n-3) is reported. Dams were fed graded levels of LA during gestation and lactation, and the pups were maintained on the diet of their dams until the end of the brain growth spurt at 30 d of life. Milk, and pup brain, retina, liver, and plasma were analyzed quantitatively for fatty acid profile. The percentage of docosahexaenoic acid (DHA, 22:6n-3) in retina increased from an LA-deficient dietary level, peaked at the 9:1 (LA/ALA) level, then fell for the 41:1 and 69:1 levels. In contrast, the brain DHA percentage was unaffected by dietary LA levels. Retinal unsaturated fatty acid levels paralleled liver and plasma levels. The milk fatty acid composition mirrored the diets. These data show that the retinal fatty acid composition responds sensitively to dietary fatty acid composition, similar to liver and plasma, while the brain unsaturate composition is nearly independent of dietary composition.

Influence of feeding artificial-formula milks containing docosahexaenoic and arachidonic acids on the postnatal long-chain polyunsaturated fatty acid status of healthy preterm infants

In view of the importance of long-chain polyunsaturated fatty acids (LCP) for growth and development of fetal and infant neural tissue, the influence of the dietary n-3 and n-6 LCP intake on the LCP status of forty-three preterm infants (birth weight < 1800 g) was studied. Thirty-one formula-fed infants were randomly assigned to receive a conventional formula lacking LCP (n 16), or an 22:6n-3- and 20:4n-6-enriched formula (n 15); twelve infants received their own mother's breast milk. Fatty acid compositions of plasma and erythrocyte (RBC) phospholipids (PL) were determined in umbilical venous blood, in weekly postnatal samples until day 35 of life and, for the formula-fed infants, at 3 months of corrected age. Both in plasma (P < 0.001) and RBC (P < 0.01) PL, the changes with time until day 35 for 22:6n-3 and 20:4n-6 in the two groups of formula-fed infants were significantly different, with higher values, comparable with those of human-milk-fed infants, in the LCP-enriched-formula group. At 3 months of corrected age, differences between the two formula-fed groups were even more pronounced. In conclusion, adding 22:6n-3 and 20:4n-6 to artificial formulas in balanced ratios and in amounts similar to those found in preterm human milk raises both the 22:6n-3 and the 20:4n-6 status of formulated preterm infants to values found for human-milk-fed preterm infants. Additional studies are necessary to evaluate the potentially favourable effects of this combined addition on the neurodevelopmental outcome of preterm infants.

Essential fatty acid status of fetal plasma phospholipids: similar to postnatal values obtained at comparable gestational ages

Hardly any direct information is available on the essential fatty acid (EFA) status of the fetus during intrauterine development. Therefore, we studied 86 umbilical plasma samples obtained by trans-abdominal puncture during ongoing pregnancies (18.3-39.0 weeks of gestational age). These were compared with 51 samples of umbilical cord blood, collected immediately after birth (gestational ages, 28.5-39 weeks). The total amounts of fatty acids in fetal plasma phospholipids (mg/l) did not change during gestation. The relative amounts of linoleic acid (% of total fatty acids) showed a slight increase (P = 0.03) during fetal maturation. Arachidonic acid (20:4n-6) decreased (both absolute (mg/l) and relative (% wt/wt) P < or = 0.0001), while docosahexaenoic acid (22:6n-3) increased (absolute P < 0.003, relative P < 0.0001) when pregnancy progressed. The EFA profiles of fetal samples were in general comparable with postnatal results of infants born at similar gestational ages. However, the fetal linoleic acid status was lower than the linoleic acid status of the neonates. The same was true for the overall EFA status. The results of this study indicate that the low EFA status observed in preterm infants at birth, is a developmentally related phenomenon.

Visual evoked potentials and dietary long chain polyunsaturated fatty acids in preterm infants

The influence of dietary long chain polyunsaturated fatty acid (LCP) supply, and especially of docosahexaenoic acid (DHA), on evoked potential maturation, was studied in 58 healthy preterm infants using flash visual evoked potentials (VEPs), flash electroretinography (ERG), and brainstem acoustic evoked potentials (BAEPs) at 52 weeks of postconceptional age. At the same time, the fatty acid composition of red blood cell membranes was examined. The infants were fed on breast milk (n = 12), a preterm formula supplemented with LCP (PF-LCP) (n = 21), or a traditional preterm formula (PF) (n = 25). In the breast milk and PF-LCP groups the morphology and latencies of the waves that reflect the visual projecting system were similar; in the PF group the morphology was quite different and the wave latencies were significantly longer. This could mean that the maturation pattern of VEPs in preterm infants who did not receive LCP was slower. Moreover, a higher level of erythrocyte LCP, especially DHA, was found in breast milk and PF-LCP groups compared with the PF group. ERG and BAEP recordings were the same in all three groups. These results suggest that a well balanced LCP supplement in preterm formulas can positively influence the maturation of visual evoked potentials in preterm infants when breast milk is not available.

Long chain polyunsaturated fatty acids and visual function in preterm infants

Electroretinograms (ERG) were recorded at 40 weeks post-conceptual age (PCA) in 18 infants born prematurely (25-32 weeks gestation). Fatty acid composition of plasma and red cell phospholipids was measured within 4 days of birth and at time of ERG testing, and detailed record was kept of dietary intake. Correlations were seen between percentage intake of breast milk and docosahexaenoic acid (DHA) in both plasma (r = 0.818, P < 0.0001) and red cells (r = 0.534, P = 0.035) and significant differences in fatty acid profiles were seen between infants receiving > 50% and < 50% breast milk. No difference was seen in retinal sensitivity between infants receiving > 50% or < 50% breast milk. A positive correlation was seen between scotopic (rod) b-wave implicit time on ERG and DHA in both plasma (r = 0.733, P = 0.001) and red cells (r = 0.502, P = 0.04). A positive correlation was seen between arachidonic acid and rod ERG amplitude (r = 0.565, P = 0.022) which may reflect the higher AA/DHA ratio in the developing retina. These data did not support our hypothesis that increased dietary DHA results in enhanced retinal maturation. Visual acuity measured at 40 weeks PCA and again 3 months later was similar between groups. While subtle relationships were demonstrated between long chain polyunsaturated fatty acids and visual function, all infants were felt to be within age-appropriate normal range at expected date of delivery and at 3 months corrected age.

Fatty acid metabolism in phenylketonuria

Children treated for phenylketonuria (PKU) have a low intake of whole animal foods. Consequently, the dietary intake of long-chain polyunsaturated fatty acids (PUFA) is just a few milligrams per day, mostly represented by arachidonic acid (AA). In a consecutive series of studies, we assessed in treated PKU children their long-chain PUFA status, the AA-related eicosanoid synthesis and the effects of specific PUFA supplementations. We found that the good compliance with the dietary regimen negatively influences the long-chain PUFA status and serum eicosanoid release from platelets. Supplementation with either marine or blackcurrant oils modifies the long-chain PUFA status of PKU children without approaching the fatty acid pattern of a healthy control population. Good-compliant PKU patients have diet-related, low levels of circulating long-chain PUFA, whose clinical and functional consequences deserve further investigation. The effects of dietary supplementations with long-chain PUFA of both the n-6 and n-3 series should be carefully evaluated.

The very low birth weight premature infant is capable of synthesizing arachidonic and docosahexaenoic acids from linoleic and linolenic acids

Infants fed formulas devoid of long-chain polyunsaturated fatty acids (LCP) exhibit low plasma LCP concentrations and have poorer retinal and neurologic development in comparison with their human milk-fed counterparts. It is not known whether the low plasma LCP concentrations result from an impaired biosynthetic capacity, a high need or a low dietary intake. With stable isotope technology and high sensitivity tracer detection using gas chromatography-isotope ratio mass spectrometry we measured the conversion of [13C]linoleic acid (C18:2n-6) and [13C]linolenic acid (C18:3n-3) into their longer chain derivatives in five 1-mo-old formula-fed preterm infants (birth weight 1.17 +/- 0.12.kg and gestational age 28.4 +/- 1.3 wk). Carbon-13-labeled linoleic acid and inolenic were mixed with the formula and administered continuously for 48 h. Both tracers were rapidly incorporated in plasma phospholipids, and their metabolic products including arachidonic acid (C20:4n-6) and docosahexaenoic acid (C22:6n-3) became highly enriched. We demonstrate that the preterm infant is capable of synthesizing LCP from their 18-carbon precursors, and our data do not support the hypothesis that a reduced delta 6 desaturation is a main factor leading to low arachidonic acid and docosahexaenoic acid levels.

Biosynthesis of docosahexaenoic acid in human cells: evidence that two different delta 6-desaturase activities may exist

It has been proposed that synthesis of docosahexaenoic acid (22:6(n-3) in rat hepatocytes occurs by a route independent of delta 4-desaturase, which involves delta 6-desaturation and retroconversion (Voss A., Reinhart M., Sankarappa S. and Sprecher H. (1991) J. Biol. Chem. 266, 19995-20000). However, most cells exhibit these enzymatic activities and nevertheless synthesize low to undectectable amounts of 22:6(n-3). Moreover, there are few data on the occurrence of this pathway in human cells. In the present work, we have analysed the biosynthetic pathway of 22:6(n-3) in human Y-79 retinoblastoma and Jurkat T-cells. Y-79 cells were supplemented with 18:3(n-3) and 20:5(n-3) or incubated with [1-14C]18:3(n-3) and [1-14C]20:5(n-3) and lipids analysed by argentation TLC, reverse-phase TLC and GLC-mass spectrometry. Pulse-chase experiments revealed that synthesis of 22:6(n-3) from 20:5(n-3) in Y-79 cells occurred through two successive elongations, followed by a delta 6-desaturation of 24:5(n-3) to 24:6(n-3) and retroconversion to 22:6(n-3). Incubation of Y-79 cells with [1-14C]18:3(n-3) in medium containing 50 microM trans-9,12-18:2, a potent inhibitor of delta 6-desaturase, caused a reduction of 22:6(n-3) synthesis mainly by interfering with the desaturation of 18:3(n-3). However, when [1-14C]20:5(n-3) was used as precursor, synthesis of 22:6(n-3) was depressed to a lesser extent and mainly by reduction of 24:6(n-3) retroconversion. Neuronal differentiation of Y-79 cells caused a great increase in delta 6-desaturase activity on 18:3(n-3), though the amount of 22:6(n-3) synthesized did not change or diminish, suggesting the existence of a particular delta 6-desaturase involved in the synthesis of 22:6(n-3). The existence of a distinctive delta 6-desaturase activity could also explain why Jurkat cells growing in serum-free medium showed a near 3-fold increase in the synthesis of pentaenes from 18:3(n-3) and, at the same time, a large decrease in the synthesis of 22:6(n-3). The verification of the involvement of two delta 6-desaturase activities in 22:6(n-3) synthesis would have important implications for the formulation of the nutritional requirements of this fatty acid during development.

Special properties of human milk

In this review, several nutritional and nonnutritive differences between mothers' milk and formula and their relationship to neonatal gastrointestinal and immune processes are discussed. The dynamic relationship of human milk as evidenced by its changing composition, unique bioactive and immunologic properties, and specialized cellular components is further delineated. The clinical significance and relevance of these findings to the clinician are then presented. Lastly, educational strategies, their effectiveness in promoting breastfeeding, and an approach that might be taken by the clinician to encourage breastfeeding are outlined.

Long-chain polyunsaturated fatty acid content in Dutch preterm breast milk; differences in the concentrations of docosahexaenoic acid and arachidonic acid due to length of gestation

Recognizing the important role of long-chain polyunsaturated fatty acids (LCP) particularly in preterm infant nutrition, we studied the fatty acid composition of breast milk from 65 mothers of very preterm ( < 31 weeks of gestation) and preterm ( > or = 31 and < 36 weeks of gestation) infants. Fatty acids were determined as fatty acid methyl esters by capillary gas chromatography. In accordance with other studies, the increase of capric acid, lauric acid and myristic acid during lactation is influenced by prematurity. Unsaturated fatty acids had the inclination to decrease. Our interest was mainly focused on docosahexaenoic acid (DHA) and arachidonic acid (AA). Accelerated brain growth during the last trimester of gestation requires an extra need for these LCPs. In our study, preterm milk after a gestation period of at least 32 weeks contained the highest amounts of DHA and AA. The Western maternal diet is considered to be low in omega 3 fatty acids, that is why the concentration of DHA in our preterm milk can be regarded as a low amount. As it is the milk of their mothers, and because the amounts are higher than normally found in Western full term breast milk, the contribution of DHA to preterm milk fat (0.34%) might be considered, for the time being, as a safe natural guideline for formulas for preterm infants.

Effect of dietary docosahexaenoic acid on brain composition and neural function in term infants

There is a need to determine whether there is a dietary requirement for docosahexaenoic acid (DHA, 22:6n-3) by term infants to achieve their full developmental potential. Studies of brain fatty acid composition demonstrated that infants who were breast fed had greater levels of cerebral cortex DHA than did infants who were formula fed, suggesting that DHA in the cerebrum is dependent on a supply in the diet. Some physiological studies reported that electrophysiological and behavioral assessments of visual function were improved in breast-fed infants relative to those fed formula and that this was related to the length of breast feeding. While some randomized studies of DHA supplementation of infant formula to term infants demonstrated that the visual function of formula-fed infants could be improved to breast-fed levels by adding DHA to formula, others failed to demonstrate an effect. Variations in dietary treatments and methods of assessment make comparison of the studies difficult. Further work is necessary to rigorously establish if there are long-term benefits of dietary DHA to the term infant.

Role of essential fatty acids in the function of the developing nervous system

The basis for n-3 fatty acid essentially in humans includes not only biochemical evidence but functional measures associated with n-3 deficiency in human and nonhuman primates. Functional development of the retina and the occipital cortex are affected by alpha-linolenic acid deficiency and by a lack of docosahexaenoic acid (DHA) in preterm infant formulas and, as reported more recently, in term diets. Functional effects of n-3 supply on sleep-wake cycles and heart rate rhythms support the need for dietary n-3 fatty acids during early development. Our results indicate that n-3 long-chain polyunsaturated fatty acids should be considered provisionally essential for infant nutrition. DHA may also be required by individuals with inherited metabolic defects in elongation and desaturation activity, such as patients with peroxisomal disorders and some forms of retinitis pigmentosa.

Fatty acid composition of human milk in Spain

The fatty acid composition of mature human milk obtained from 40 Spanish women was analyzed by capillary gas chromatography. The women were from two regions in Spain, Navarre and Catalonia. Milk samples were collected between 20 and 30 days postpartum. The fatty acid composition was expressed as weight percentage (% wt/wt of all fatty acids detected with a C8 to C22 chain length). Monounsaturated fatty acids represent 41.97%, mostly 18:1 n-9/n-7 (38.39%). The second major fraction was formed by saturated fatty acids, 41.09%. Polyunsaturated fatty acid fraction (15.23%), included seven long chain polyunsaturated fatty acids (LCPs; 2.21%). Among LCPs, 1.6% accounted for the n-6 series and 0.64% for the n-3 series. LCPn-6/LCPn-3 ratio was 2.51. Mothers reporting a high fish consumption showed higher (p < 0.05) 22:6 n-3 and 20:5 n-3 content. The use of olive oil as the preferential fat source showed higher 18:1 n-9/n-7 and lower 18:2 n-6 content (p < 0.0001), while the use of sunflower oil instead of olive oil significantly (p < 0.0001) increased 18:2 n-6 and decreased 18:1 n-9/n-7. Regional differences (p < 0.05) were detected only for the n-6 LCP and the total LCP content. The higher n-6 LCP and total LCP content was found in Navarre. This could have been due to different diet habits, like higher egg consumption.

Biochemical effects of dietary linoleic/alpha-linolenic acid ratio in term infants

Recent statements concerning linoleic (LA) and alpha-linolenic acid (LNA) intakes for infants include a desirable range of LA/LNA ratios. To evaluate several dietary LA/LNA ratios, the fatty acid patterns of plasma and erythrocyte phospholipid fractions, as well as plasma total lipid fractions, were determined shortly after birth and at 21, 60, and 120 d of age in term infants fed formula with 16% of fat as LA and either 0.4, 0.95, 1.7, or 3.2% as LNA (LA/LNA ratios of approximately 44, 18, 10, and 5). The content of all n-3 fatty acids in both plasma fractions was higher at all times in infants who received the highest LNA intake; however, the docosahexaenoic acid (DHA) content was only half that shortly after birth or reported in breast-fed infants of comparable ages. The LA content of plasma lipids of all groups was higher at all times than shortly after birth but did not differ among groups. The arachidonic acid (AA) content was higher in infants who received the lowest LNA intake, but only half that at birth or reported in breast-fed infants. In contrast, the DHA content of the erythrocyte phospholipid fraction did not differ among groups until 120 d of age when it was higher in those who received the highest LNA intake and the AA content of this fraction did not differ among groups at any time. These data demonstrate that dietary LA/LNA ratios between 5 and 44 do not result in plasma or erythrocyte lipid levels of DHA or plasma lipid levels of AA similar to those at birth or reported by others in breast-fed infants. However, the data indicate that the LA/LNA ratio of the formula is an important determinant of the amounts of DHA and AA required to achieve plasma and erythrocyte levels of these fatty acids similar to those of breast-fed infants.

Fatty acids in pediatric nutrition

The past 20 years have shown that dietary FA molecules are able to mediate and condition biologic functions in an increasing number of biochemical contexts. Different diet interventions can induce measurable alterations at the ultrastructural level of lipid moieties and circulating FAs. This has many consequences for prevention, for therapy, and, in particular, for the management of chronic degenerative disease. From the earliest stages of life, an adequate availability of the n-6 and n-3 series LCP seems essential to ensure the adequate structural and functional development of the various tissues, especially the central nervous system tissues. Recognition of the numerous steps involved in intermediate FA metabolism should induce us to further our understanding of the manifold possibilities open for intervention on FA profile and balance and stress the need for an interdisciplinary approach.

Growth, fatty acid composition of plasma lipid classes, and plasma retinol and alpha-tocopherol concentrations in full-term infants fed formula enriched with omega-6 and omega-3 long-chain polyunsaturated fatty acids

Full-term infants fed formula without dietary long-chain polyunsaturated fatty acids (LCF) exhibit significantly lower plasma LCP values than breast-fed infants. We studied prospectively two groups of healthy full-term infants fed conventional infant formula without LCP (F, n = 10) or the same formula enriched with both omega-6 and omega-3 LCP (LCP-F, n = 12). Anthropometric data were obtained and fatty acid (FA) compositions of plasma phospholipids, triglycerides and sterol esters as well as plasma retinol and alpha-tocopherol concentrations were determined at 5 days and 1, 2, 3 and 4 months of age. Gains in weight, length and head circumference did not differ between the two groups throughout the study period. Plasma FA values did not differ at 5 days of age. Between 1 and 4 months of age, plasma phospholipids of infants fed LCP-F consistently had significantly (p < 0.05) higher percentages of arachidonic acid (1 month: 9.7 (0.8) versus 7.0 (1.3) %wt/wt, 4 months: 8.7 (0.5) versus 6.6 (1.0) %wt/wt, median (interquartile range), LCP-F versus F) and docosahexaenoic acid (1 month: 2.9 (0.5) versus 1.6 (0.3) %wt/wt; 4 months: 2.9 (0.4) versus 0.9 (0.3) %wt/wt). Plasma retinol and alpha-tocopherol concentrations did not differ between the two groups throughout the study. We conclude that this form of LCP enrichment of formula for full-term infants effectively enhances plasma LCP contents without detectable adverse effects. The potential effects on functional outcome need to be studied carefully in prospective clinical trials.

Lipid profiles of cerebral gray matter and livers of macaque monkeys Macaca fascicularis and Macaca fuscata fuscata: a comparative study during development

The lipid and fatty acid profiles in cerebral gray matter and livers were studied in macaque monkeys (Macaca fascicularis and M. fuscata fuscata) of different ages. In cerebral gray matter, the phosphatidylcholine/phosphatidylethanolamine (PC/PE) ratio decreased in animals more than 3 years old, while the cholesterol/lipid-phosphorus ratios and the unsaturation indices increased, as compared with those in fetuses and newborns. The level of 22:6n-3 in PE of cerebral gray matter increased up to 3 years old, mainly by replacing 20:4n-6, whereas the level in phosphatidylserine did not change significantly with age. The hepatic lipid-phosphorus levels and PC/PE ratios were lower in newborns than in animals more than 3 years old. The level of 22:6n-3 in liver phospholipid did not change, while that of 20:4n-6 was lower in animals more than 3 years old than in newborns.

Polyunsaturated fatty acids in the developing human brain, erythrocytes and plasma in peroxisomal disease: therapeutic implications

Patients with Zellweger syndrome and related peroxisomal disorders have profound changes in the polyunsaturated fatty acid (PUFA) patterns in brain and other tissues, with a constant decrease in docosahexaenoic acid (DHA, 22: 6omega3) concentration. Arachidonic acid (AA, 20: 4omega6) concentration is normal or increased and linoleic acid (LA, 18: 2omega6) is increased in the brain of Zellweger patients. In the retina of these patients, the levels of DHA are extremely low. Since these alterations are reflected elsewhere, they can be detected in vivo in patients with generalized peroxisomal disorders by measuring the PUFA content of plasma and erythrocytes, which show very low concentrations of DHA. The concentration of AA is low in plasma in generalized peroxisomal patients, although it is within normal limits in erythrocytes. Patients with X-linked adrenoleukodystrophy (X-ALD) or adrenomyeloneuropathy (AMN) have a normal DHA and AA content in both plasma and erythrocytes, unless they receive extremely low-PUFA diets. Given the probable role of DHA deficiency in the pathogenesis of Zellweger syndrome (ZS), it is important to normalize concentrations of DHA, at least in blood, in an attempt to correct the DHA deficiency in brain. DHA ethyl ester was given orally to two infants with a peroxisome deficiency disorder for a year, and some favourable biochemical changes were produced in erythrocytes and plasma. Normalization of the DHA concentrations in erythrocytes was obtained in about 2 months, and the ratios 26: 0/22: 0 and 26: 1/22: 0 decreased markedly in plasma in the two patients. The plasmalogen ratio 18: 0 dimethyl acetal/18: 0 in erythrocytes increased to virtually normal values in both patients. There was a clear clinical improvement in the two patients, which paralleled the increase in blood DHA. The concentrations of AA and other PUFAs were closely monitored and, when necessary, AA was added to the diet. Such a DHA therapy, given under close biochemical and clinical control, and accompanied by a diet rich in other long-chain PUFA, is strongly recommended in all patients with peroxisomal disorders in whom a DHA deficiency is detected in blood.

Essential fatty acids in full term infants fed breast milk or formula

To determine the biochemical effects of the fatty acid composition of plasma lipids, two groups of 10 healthy full term infants who were either exclusively breast fed or received a formula with similar contents of linoleic and alpha linolenic acids, but without long chain polyunsaturated (LCP) fatty acids, were studied prospectively. Plasma phospholipid, triglyceride, and sterol ester fatty acids were determined at the age of 2, 4, and 8 weeks by high resolution capillary gas chromatography. Breast fed infants maintained stable LCP fatty acid concentrations throughout the study. Formula fed infants had significantly lower median values of arachidonic acid (AA) at the ages of 2 (6.9 v 9.5% wt/wt) and 4 weeks (5.9 v 7.9%) and docosahexaenoic acid (DHA) at the ages of 4 (1.1 v 1.7%) and 8 weeks (1.0 v 1.7%) in plasma phospholipids. Median AA values in triglycerides were also significantly lower in the infants receiving formula at the ages of 2 (0.4 v 0.6%) and 4 weeks (0.3 v 0.6%). It is concluded that formula fed full term infants are unable to match the omega-3 and omega-6 LCP status of breast fed full term infants until at least two months after birth.

Effect of three intravenously administered fat emulsions containing different concentrations of fatty acids on the plasma fatty acid composition of premature infants

The effects of an intravenously administered lipid emulsion supplemented with gamma-linolenic acid on the fatty acid profile of premature infants were compared with those of two conventional lipid emulsions. Fifty-nine premature neonates receiving total parenteral nutrition were randomly assigned to receive either fat emulsion containing gamma-linolenic acid and long-chain triglycerides (LCT), an LCT emulsion, or a 50% (wt/wt) mixture of medium-chain triglycerides and LCT emulsion. Forty-nine infants completed the study. During the 6-day study there was a significant tenfold increase in the plasma levels of gamma-linoleic acid in the supplemented group versus the other two groups. A significant threefold to fivefold increase in the omega 6 long-chain polyunsaturated fatty acids was observed in all groups. These changes seemed to be attributable mostly to linoleic acid from the lipid emulsion, despite the 50% lower dose in the medium- and long-chain triglycerides group. The increase in the omega 3 long-chain polyunsaturated fatty acids also was mainly caused by a similar increase in the level of alpha-linolenic acid. No differences were recorded in the linoleic/alpha-linolenic acid ratio among the groups. Plasma levels of some of the semiessential fatty acids were significantly higher in the medium- and long-chain triglycerides group than in the LCT group. This may be related to slower elimination of LCT, to the difference between emulsions, or to less substrate inhibition on delta-6-desaturase, which seems to be less of a rate-limiting enzyme than previously considered. Further intravenous feeding trials are needed to identify the optimal balance of fatty acids for nutrition of these premature infants.

Controversies in the composition of infant formulas

Available infant formulas contain a vast assortment of carbohydrate, protein, and fat sources in an effort to emulate the composition of human milk. Although infants receiving commercial formulas thrive, physicians should be cognizant of differences in formula composition and the research that has resulted in the differences. Such awareness permits rational and scientific recommendations both in prescription of formulas and in direction of research on the optimal formula composition for infants.

Blood polyunsaturated fatty acids in patients with peroxisomal disorders. A multicenter study

The purpose of the study was to compare the polyunsaturated fatty acid (PUFA) status in patients with X-linked adrenoleukodystrophy or adrenomyeloneuropathy (X-ALD/AMN) with that in disorders of peroxisome biogenesis (PB). Total fatty acids and plasmalogens were quantified in plasma and red cells from 28 patients with X-ALD/AMN, 26 patients with generalized peroxisomal disorders, and 37 controls. Total fatty acid methyl esters and plasmalogen dimethyl acetals were obtained by direct transmethylation and separated by capillary column gas chromatography. The results confirm previous findings in that docosahexaenoic acid (DHA, 22:6n-3) was greatly decreased in both plasma and erythrocytes from patients with PB disorders. When nutritional conditions were adequate, patients with X-ALD/AMN had normal levels of DHA. A highly significant positive correlation was found between the levels of DHA and those of plasmalogens in peroxisomal patients. As in other tissues, the parent n-6 fatty acid, linoleic acid (LA, 18:2n-6) was significantly increased in red cells from PB patients, whereas arachidonic acid (20:4n-6) was virtually within normal limits. In clear contrast to red cells and other tissues, arachidonate was significantly lower in plasma from PB patients. The decrease in plasma arachidonate and the high tissue levels of LA suggest a defect of delta 6 desaturase and/or delta 5 desaturase in PB patients. The n-6 fatty acids were normal in X-ALD/AMN patients. The present data show that X-ALD/AMN patients do not have the profound PUFA alterations that PB patients have, at least in blood.

Effect of maternal dietary arachidonic or linoleic acid on rat pup fatty acid profiles

Rapidly growing neonatal mammals accrete relatively large quantities of long chain (> or = C20) polyunsaturated fatty acids (LCP) in membrane phospholipids. We have examined accumulation of omega 6 LCP in suckling neonatal rat pups during the first 14 d of life when their dams received essential fatty acids in the form of triglycerides containing linoleic acid or arachidonic acid. Dietary levels of these fatty acids were either 1 or 5% of total dietary fatty acids. The fatty acid profile of pup stomach contents (composed solely of the dams' milk) and plasma lipids, as well as liver and brain phospholipids, were determined. Stomach linoleic and arachidonic acid levels reflected the diet of the dams. Pup plasma and liver arachidonic acid levels increased progressively from the group receiving 1% linoleic acid to 5% linoleic acid and from 1% arachidonic acid to 5% arachidonic acid. Interestingly, brain phosphatidylethanolamine and phosphatidylcholine arachidonic acid levels were more stable than plasma or liver levels. These results suggest that the brain may be capable of either selective transport of omega 6 LCP or chain elongation/desaturation of linoleic acid. These data indicate that care must be exercised when adding LCP to infant formula since widely divergent accretion rates of arachidonic acid may occur in various tissues.

Cerebral cortex docosahexaenoic acid is lower in formula-fed than in breast-fed infants

Docosahexaenoic acid (22:6n-3) is abundant in the brain and retina and may be important for optimal nervous system development. Although current infant formulas available in the United States do not contain this fatty acid, it is found in human milk. In a recent study, the concentration of 22:6n-3 in cerebral cortex phospholipids was lower in full-term formula-fed infants than in infants who were breast-fed.