Visual acuity and the essentiality of docosahexaenoic acid and arachidonic acid in the diet of term infants

A randomized trial of different ratios of linoleic to alpha-linolenic acid in the diet of term infants: effects on visual function and growth

BACKGROUND

There are nutritional recommendations that the ratio of linoleic to alpha-linolenic acid (LA:ALA) in formula for term infants be between 5:1 and 15:1. These recommendations were made in the absence of data on functional or clinical outcomes.

OBJECTIVE

We compared the fatty acid status, visual evoked potential (VEP) acuity, and growth of term infants fed formula containing an LA:ALA of 10:1 or 5:1 with those of a breast-fed reference cohort.

DESIGN

Formula-fed infants were allocated randomly in a double-blind fashion to receive formula with an LA:ALA of either 10:1 (16.9:1.7; n = 36) or 5:1 (16.3:3.3; n = 37) from near birth to 34 wk of age. Increased ALA was attained by replacing soy oil with low-erucic acid cannola oil. A parallel group of breast-fed infants was also recruited. Infant growth and fatty acid status were assessed at 6, 16, and 34 wk of age. VEP acuity was assessed at 16 and 34 wk.

RESULTS

Infants fed the 5:1 formula had greater docosahexaenoic acid (DHA) concentrations in plasma and erythrocyte phospholipids than did infants fed the 10:1 formula, but DHA concentrations of infants fed the 5:1 formula remained less than those in breast-fed infants. The VEP acuity of all formula-fed and breast-fed infants was not significantly different at 16 and 34 wk of age. At birth, infants fed the 5:1 formula were heavier, were longer, and had a greater head circumference than infants assigned to the 10:1 formula group; this differential was maintained throughout the trial. The rate of gain in weight, length, and head circumference was not significantly different between the 2 formula-fed groups, although breast-fed infants had lower weight and length gains than did formula-fed infants between 16 and 34 wk of age.

CONCLUSION

Lowering the LA:ALA in formula from 10:1 to 5:1 by using low-erucic acid canola oil resulted in a modest increase in plasma DHA but had no effect on VEP acuity or growth rate.

A critical appraisal of the role of dietary long-chain polyunsaturated fatty acids on neural indices of term infants: a randomized, controlled trial

OBJECTIVE

To determine whether dietary long-chain polyunsaturated fatty acids (LCPUFA), such as docosahexaenoic acid (DHA) and arachidonic acid, affect visual evoked potential (VEP) acuity of formula-fed infants, relative to breastfed infants. A secondary objective was to assess the effect of LCPUFA on Bayley's mental developmental index (MDI) and psychomotor developmental index (PDI).

METHODS

Formula-fed infants were randomly allocated, in a double-blind manner, to either a placebo (no LCPUFA; n = 21), DHA supplemented (n = 23), or DHA+arachidonic acid supplemented formula (n = 24). Infants were fed their assigned formula from the first week of life until 1 year of age. A parallel reference group of breastfed infants was recruited and followed (n = 46). Infant VEP acuity was assessed at 16 and 34 weeks, and Bayley's MDI and PDI were assessed at 1 and 2 years of age.

RESULTS

There were no differences among the randomized formula groups for VEP acuity at either 16 or 34 weeks of age. Breastfed infants had better VEP acuity at 34 weeks of age, but not at 16 weeks, compared with all formula-fed infants. Bayley's MDI and PDI were similar in the 3 formula-fed groups at 1 and 2 years. Breastfed infants had higher MDI scores than formula-fed infants at 2 years of age even after adjusting for environmental variables.

CONCLUSIONS

LCPUFA supplementation did not influence VEP acuity development in these well-nourished, formula-fed infants.

n-3 polyunsaturated fatty acid requirements of term infants

The benchmarks for human nutrient requirements are the recommended dietary intakes (RDIs). However, the RDIs are set to prevent a clinical deficiency state in an otherwise healthy population and there are few nutrient recommendations set with the goal of achieving an optimal or maximal state of nutrition and health. This is becoming an increasing challenge with the introduction of many nutraceuticals and functional foods, a prime example being the debate surrounding the introduction of long-chain polyunsaturated fatty acids (LCPUFAs) into infant formulas. Most expert nutrition committees have used the fatty acid composition of breast milk as a basis for recommendations for infant formulas, with little information on the minimum absolute requirement for essential PUFAs. It has been difficult to determine a minimum requirement for fatty acids because 1) LCPUFAs can be synthesized from precursor fatty acids, 2) plasma n-3 LCPUFA concentrations representing deficiency and sufficiency are not clearly defined, and 3) there are no recognized clinical tests for n-3 LCPUFA deficiency and sufficiency. Therefore, there is a clear need to associate a measure of LCPUFA status with a specific functional outcome before any recommendations can be made for achieving optimal or maximal LCPUFA status.

Cloning, expression, and fatty acid regulation of the human delta-5 desaturase

Arachidonic (20:4(n-6)), eicosapentaenoic (20:5(n-3)), and docosahexaenoic (22:6(n-3)) acids are major components of brain and retina phospholipids, substrates for eicosanoid production, and regulators of nuclear transcription factors. One of the two rate-limiting steps in the production of these polyenoic fatty acids is the desaturation of 20:3(n-6) and 20:4(n-3) by Delta-5 desaturase. This report describes the cloning and expression of the human Delta-5 desaturase, and it compares the structural characteristics and nutritional regulation of the Delta-5 and Delta-6 desaturases. The open reading frame of the human Delta-5 desaturase encodes a 444-amino acid peptide which is identical in size to the Delta-6 desaturase and which shares 61% identity with the human Delta-6 desaturase. The Delta-5 desaturase contains two membrane-spanning domains, three histidine-rich regions, and a cytochrome b(5) domain that all align perfectly with the same domains located in the Delta-6 desaturase. Expression of the open reading frame in Chinese hamster ovary cells instilled the ability to convert 20:3(n-6) to 20:4(n-6). Northern analysis revealed that many human tissues including skeletal muscle, lung, placenta, kidney, and pancreas expressed Delta-5 desaturase mRNA, but Delta-5 desaturase was most abundant in the liver, brain, and heart. However, in all tissues, the abundance of Delta-5 desaturase mRNA was much lower than that observed for the Delta-6 desaturase. When rats were fed a diet containing 10% safflower oil or menhaden fish oil, the level of hepatic mRNA for Delta-5 and Delta-6 desaturase was only 25% of that found in the liver of rats fed a fat-free diet or a diet containing triolein. Finally, a BLAST and Genemap search of the human genome revealed that the Delta-5 and Delta-6 desaturase genes reside in reverse orientation on chromosome 11 and that they are separated by <11,000 base pairs.

Efficacy and safety of long-chain polyunsaturated fatty acid supplementation of infant-formula milk: a randomised trial

BACKGROUND

We tested whether addition of n-3 and n-6 long-chain polyunsaturated fatty acids (LCPUFA) to infant-formula milk during the first 6 months promotes long-term cognitive and motor development, without adverse consequences.

METHODS

We did a double-blind, randomised, controlled, efficacy and safety trial of formula with and without LCPUFAs, with an additional breastfed reference group, in four hospitals in two cities in the UK. The participants were 447 healthy full-term babies. 309 were fed formula (155 without LCPUFAs) and 138 were breastfed for at least 6 weeks. The main outcome measures were: Bayley Mental and Psychomotor Development Indices (MDI, PDI) at 18 months (primary efficacy outcome) and Knobloch, Passamanick, and Sherrards test at 9 months (secondary outcome). Principal safety outcomes were: infection, atopy, growth, and gastrointestinal tolerance.

FINDINGS

Babies fed formula with and without LCPUFA did not differ in cognitive or motor development, growth, infection, atopy or tolerance. The mean (95% CI) MDI was 0.5 (-2.7 to 3.8) units and the PDI 0.6 (-1.8 to 3.0) units higher in the supplementation group. Formula-fed infants had similar developmental scores to the breastfed reference group after adjustment for higher social class and maternal education in the latter.

INTERPRETATION

There was no evidence of a beneficial or adverse effect on cognitive and motor development or growth up to 18 months. Although no significant differences in safety outcomes were observed, we suggest such data should be collected in future LCPUFA trials. Our trial does not provide support for addition of LCPUFA to standard infant formula but we are now doing further follow-up of this cohort.

Dietary phospholipid alters biliary lipid composition in formula-fed piglets

Plasma cholesterol, arachidonic acid (AA, 20:4n-6), and docosahexaenoic acid (DHA, 22:6n-3) are higher in breast-fed infants than in infants fed formula without cholesterol, AA, or DHA. This study investigated differences in plasma, hepatic, and bile lipids and phospholipid fatty acids, and expression of hepatic proteins involved in sterol metabolism that result from feeding formula with cholesterol with egg phospholipid to provide AA and DHA. For this study, three groups of piglets were evaluated: piglets fed formula with 0.65 mmol/L cholesterol, the same formula with 0.8% AA and 0.2% DHA from egg phospholipid, and piglets fed sow milk. Piglets fed the formula with phospholipid AA and DHA had higher plasma high density lipoprotein, but not apoprotein (apo) B cholesterol or triglyceride; higher bile acid and phospholipid concentrations in bile; and higher liver and bile phospholipid AA and DHA than piglets fed formula without AA and DHA (P < 0.05). Hydroxy methylglutaryl (HMG)-CoA reductase and 7-alpha-hydroxylase, the rate-limiting enzymes of cholesterol and bile acid synthesis, respectively, and low density lipoprotein receptor mRNA levels were not different between piglets fed formula without and with phospholipid AA and DHA, but HMG-CoA reductase and 7alpha-hydroxylase mRNA were higher, and plasma apo B containing lipoprotein cholesterol was lower in all piglets fed formula than in piglets fed milk. These studies show that supplementing formula with AA and DHA from egg phospholipid alters bile metabolism by increasing the bile AA and DHA, and bile acid and phospholipid.

Effects of postnatal ethanol exposure on brain growth and lipid composition in n-3 fatty acid-deficient and -adequate rats

The artificial rearing model was used to investigate the effects of short-term exposure to ethanol on growth and fatty acid composition of forebrain (FB) and cerebellum (CB) during the brain growth spurt in either n-3 fatty acid-adequate (AD) or n-3 deficient (DEF) rat pups. On postnatal day 5, offspring of female rats that had been fed AD or DEF diets from day 5 of life were assigned to three groups: members of two groups were gastrostomized and artificially fed formulas appropriate for their maternal history, and the third group (suckled control) was fostered to lactating dams of a similar dietary history. Half of the artificially reared pups in each dietary condition were fed ethanol in their formula (7% vol/vol) in one-quarter of their daily feedings, while the others received maltose-dextrin substituted isocalorically for ethanol. Blood alcohol concentrations did not differ between the dietary groups. FB weight on postnatal day 9 was lower in ethanol-exposed offspring in both dietary conditions. Brain fatty acid composition reflected dietary history in that, compared with AD pups, DEF pups had lower percentages of docosahexaenoic acid, higher percentages of 22:5n-6, and a higher n-6/n-3 fatty acid ratio. However, the effects of ethanol exposure were inconsistent, lowering the n-6/n-3 ratio in the phosphatidylethanolamine (PE) fraction in FB but not in CB, while increasing this ratio in the phosphatidylcholine (PC) fraction in FB of the DEF pups only. Thus, while ethanol had some effects on lipid composition, there was no difference between the dietary groups in their vulnerability to the effects of early short-term ethanol exposure on brain growth.

Noninvasive assessment of essential fatty acid status in preterm infants by buccal mucosal cell phospholipid analysis

BACKGROUND

The dietary supply of long-chain polyunsaturated fatty acids is receiving increased attention since a linkage to infant growth and development has been reported. To avoid repeated blood collections for determination of long-chain polyunsaturated fatty acid status, the authors developed and evaluated a noninvasive method for analysis of buccal mucosal cell phospholipids.

METHODS

Oral mucosal cells were gently collected with a soft cotton swab, buccal cell lipids separated by thin-layer chromatography, and fatty acid methyl esters of the phospholipid fraction prepared. Subsequently, the fatty acid methyl esters were analyzed by high-resolution gas chromatography.

RESULTS

The method allowed reliable analysis from very small amounts of oral mucosal cells, and results were well reproducible. The intraindividual coefficients of variation in four samples of three subjects were less than 5% for both arachidonic and docosahexaenoic acid. Fatty acid composition was not altered by consumption of milk formula before and after sample collection. The method was applied in a clinical trial with preterm infants fed human breast milk or assigned by double-blind randomization to preterm formula with or without arachidonic and docosahexaenoic acid. Buccal mucosal cells were collected in infants less than 14 days of age and at the postconceptional ages of 52 weeks and 64 weeks. Dietary long-chain polyunsaturated fatty acids showed a lasting influence on buccal cell phospholipid composition. In the course of the study, arachidonic and docosahexaenoic acid decreased significantly in the nonenriched formula group, whereas stable or rising values were observed in the groups receiving breast milk or enriched formula.

CONCLUSIONS

Buccal mucosal cell phospholipids are feasible for use as a noninvasive marker for long-chain polyunsaturated fatty acid status in preterm infants and yield reliable results. Dietary long-chain polyunsaturated fatty acids have a lasting influence on fatty acid composition of buccal cells in preterm babies.

Evaluation of a long-chain polyunsaturated fatty acid supplemented formula on growth, tolerance, and plasma lipids in preterm infants up to 48 weeks postconceptional age

BACKGROUND

The last trimester of pregnancy is a period of rapid accretion of long-chain polyunsaturated fatty acids, both in the central nervous system and the body as a whole. Human milk contains these fatty acids, whereas some preterm infant formulas do not. Infants fed formulas without these fatty acids have lower plasma and erythrocyte concentrations than infants fed human milk. Preclinical and clinical studies have demonstrated that single-cell sources (algal and fungal) of long-chain polyunsaturated fatty acids are bioavailable. A balanced addition of fatty acids from these oils to preterm formula results in blood fatty acid concentrations in low birth weight infants comparable to those of infants fed human milk.

METHODS

In the present study the growth, acceptance (overall incidence of discontinuation, reasons for discontinuation, overall incidence and type of individual adverse events), and plasma fatty acid concentrations were compared in three groups of infants fed a long-chain polyunsaturated fatty acid-supplemented preterm infant formula, an unsupplemented control formula, or human milk. The study was prospective, double-blind (formula groups only), and randomized (formula groups only). Two hundred eighty-eight infants were enrolled (supplemented formula group, n = 77; control formula group, n = 78; human milk group, n = 133).

RESULTS

Anthropometric measurements at enrollment, at first day of full oral feeding, and at both 40 and 48 weeks postconceptional age did not differ between the formula groups, whereas the human milk-fed group initially grew at a lower rate. The incidence of severe adverse events was rare and not significantly different between formula groups. The groups fed either human milk or supplemented formula had long-chain polyunsaturated fatty acid concentrations higher than those in the control formula group.

CONCLUSIONS

The results of this study demonstrate the safety and efficacy of a preterm formula supplemented with long-chain polyunsaturated fatty acids from single-cell oils.

Dietary long-chain polyunsaturated fatty acids do not influence growth of term infants: A randomized clinical trial

OBJECTIVE

To determine if dietary long-chain polyunsaturated fatty acids (LCPUFA) affect the growth of formula-fed infants relative to breastfed infants.

METHODS

A randomized, double-blind trial of three formula-fed groups and a parallel reference group of breastfed infants was conducted. The three treatments were a placebo (no LCPUFA), docosahexaenoic acid (DHA) supplemented, and DHA plus arachidonic acid supplemented formulas fed for 12 months. Infant weight, length, head circumference, and fatty acid status were assessed at 6, 16, 34 weeks, and 1 year of age. Anthropometrics were repeated at 2 years of age.

RESULTS

There were no differences between the randomized formula groups for weight, length, or head circumference even after adjustment for gender, gestational age, and the actual age at assessment. Post hoc regressions demonstrated a small negative association between DHA status at 16 weeks of age and weight at 1 and 2 years.

CONCLUSIONS

Dietary LCPUFA do not influence growth of healthy term infants to a clinically significant degree.

Long-chain polyunsaturated fatty acids and development of human infants

Human infants require n-6 and n-3 long-chain polyunsaturated fatty acids (LCPUFA), derivatives of the essential fatty acids, linoleate (n-6) and linolenate (n-3), for growth and neural development. Animals fed diets deficient in the essential fatty acids have low neural LCPUFA and behavioral changes that imply adverse effects on brain function. Studies of animals deficient in essential fatty acids have provided the rationale and outcomes for studies to determine whether human infants need dietary LCPUFA. After including n-3 LCPUFA in formula, preterm infants showed higher sensory function (retinal responses to light, visual acuity), visual attention characteristic of higher maturity during infancy, and higher scores on test of global development (6- and 12-mo Bayley Mental Developmental Index). In term infants, some but not all studies found higher visual acuity, 4-mo Brunet-Lezine psychomotor development, and 10-mo means-end problem solving with LCPUFA-containing formulae compared to formulae in general use. Because preterm infants have lower LCPUFA accumulation at birth than term infants, it may be easier to show benefits of dietary LCPUFA for neural development in the former group. In addition to low gestational age, other variables may influence LCPUFA accumulation at birth and determine whether a particular group of infants will respond to dietary LCPUFA. One current challenge is to identify and characterize the effects of those variables. Another is to learn the mechanisms by which LCPUFA status may influence behavior.

Polyunsaturated fatty acids in human milk and their role in early infant development

The lipid fraction of human milk represents the main source of energy for the newborn infant and supplies essential nutrients such as fat-soluble vitamins and polyunsaturated fatty acids (PUFA). The essential fatty acids linoleic and alpha-linolenic acids are precursors of long-chain polyunsaturated fatty acids (LC-PUFA), such as arachidonic (C20:4 n-6) and docosahexaenoic (C22:6 n-3) acids, present in human milk in considerable amounts. LC-PUFA are indispensable structural components of all cellular membranes, and they are incorporated in relatively large amounts during early growth of the brain and the retina. Moreover, some LC-PUFA are precursors of eicosanoids, molecules with potent biological activity that modulates various cellular and tissue processes. The supply of long-chain fatty acids has been associated with functional outcomes of the recipient infants such as visual acuity and development of cognitive functions during the first year of life. Here we discuss the PUFA composition of human milk, factors which determine and modulate milk PUFA content, and possible effects of milk LC-PUFA on infant growth and development.

The effects of dietary alpha-linolenic acid compared with docosahexaenoic acid on brain, retina, liver, and heart in the guinea pig

The aim of this study was to compare two different strategies to elevate brain, retina, liver, and heart docosahexaenoic acid (DHA) levels in guinea pigs. First, we used an increasing dose of alpha-linolenic acid (ALA) relative to a constant linoleic acid (LA) intake, and second, we used two levels of dietary DHA provided in conjunction with dietary arachidonic acid (AA). The percentage DHA and AA of total phospholipids in retina, liver, and heart, and in the brain phosphatidylethanolamine and phosphatidylcholine was studied in female pigmented guinea pigs (3 wk old) fed one of five semisynthetic diets containing 10% (w/w) lipid for 12 wk. The LA content in the diets was constant (17% of total fatty acids), with the ALA content varying from 0.05% (diet SFO), to 1% (diet Mix), and to 7% (diet CNO). Two other diets (LCP1 and LCP3) had a constant LA/ALA ratio (17.5:1) but varied in the levels of dietary AA and DHA supplementation. Diet LCP1 was structured to closely replicate the principal long chain polyunsaturated fatty acids (PUFA) found in human breast milk and contained 0.9% AA and 0.6% DHA (% of total fatty acids) whereas diet LCP3 contained 2.7% AA and 1.8% DHA. At the end of the study, animals were sacrificed and tissues taken for fatty acid analyses. We found no significant effects of diets on the growth of guinea pigs. Diets containing ALA had profoundly different effects on tissue fatty acid compositions compared with diets which contained the long chain PUFA (DHA and AA). In the retina and brain phospholipids, high-ALA diets or dietary DHA supplementation produced moderate relative increases in DHA levels. There was no change in retinal or brain AA proportions following dietary AA supplementation, even at the highest level. This was in contrast to liver and heart where tissue DHA proportions were low and AA predominated. In these latter tissues, dietary ALA had little effect on tissue DHA proportions although the proportion of AA was slightly depressed at the highest dietary ALA intake, but dietary DHA and AA supplements led to large increases (up to 10-fold) in the proportions of these PUFA. Tissue uptake of dietary AA and DHA appeared maximal for the LCP1 diet (replicate of breast milk) in the heart. There were no significant changes in the plasma levels of 11-dehydrothromboxane B2 (a thromboxane A2 metabolite) for any diet. The data confirm that dietary ALA is less effective than dietary DHA supplementation (on a gram/gram basis) in increasing tissue DHA levels and that tissues vary greatly in their response to exogenous AA and DHA, with the levels of these long chain metabolites being most resistant to change in the retina and brain compared with liver and heart. Dietary DHA markedly increased tissue DHA proportions in both liver and heart, whereas the major effect of dietary AA was in the liver. Future studies of the effects of dietary DHA and AA supplementation should examine a variety of tissues rather than focusing only on neural tissue.

Water maze performance is unaffected in artificially reared rats fed diets supplemented with arachidonic acid and docosahexaenoic acid

Four groups of male Long-Evans rats were reared artificially from postnatal d 5 to 18 by being fed through a gastrostomy tube with rat milk substitutes containing oils providing 10% linoleic acid and 1% alpha-linolenic acid (g/100 g fat); with the use of a 2 x 2 design, they were fed one of two levels of arachidonic acid (AA) and docosahexaenoic acid (DHA) (0.0 and 2.5 g/100 g of fatty acids). A fifth artificially reared group was fed a diet high in saturated fat, and a sixth group was reared by dams fed a standard AIN-93M diet. The pups were weaned onto modified AIN-93G diets, with a fat composition similar to that fed during the artificial rearing period. Behavioral testing was conducted between 6 and 9 wk of age; brain lipid composition was then assessed. Relative to the unsupplemented group (0.0 g/100 g AA and DHA), dietary supplementation resulted in a wide range of AA (84-103%) and particularly DHA (86-119%) levels in forebrain membrane phospholipids. AA supplementation increased AA levels and decreased DHA levels, and DHA supplementation increased DHA levels and decreased AA levels, with the magnitude of these effects dependent on the level of the other fatty acid. DHA levels were very low in the saturated fat group. The groups did not differ on the place or cued version of the Morris water-maze, but on a test of working memory, the saturated fat group was impaired relative to the suckled control group. Further correlational analyses in the artificially reared animals did not support a relationship between the wide range of DHA and AA levels in the forebrain and working-memory performance.

Polyunsaturated fatty acids and infant visual development: a critical appraisal of randomized clinical trials

At the Consensus and Controversies Conference held in Barcelona in November 1996, one of the sessions focused on an evaluation of the effects of dietary polyunsaturated fatty acids (PUFA) on infant visual development. The intervention trials in preterm and term infants were reviewed and discussed in detail. Results of these trials, particularly those in term infants, were inconsistent; much discussion occurred concerning the causes of these diverse results. We attempt to reflect, rather than report exactly, the discussion relating to these issues and address the clinical trials according to recently published guidelines for conduct and reporting of randomized clinical trials (RCT). Compared with these recent guidelines, the published papers of RCT involving PUFA and visual function are often incomplete, making it difficult to assess if we can have a high degree of confidence in the reported effects (or lack of effects). Despite this, valuable data relating to the effect of diet on the visual development of infants were obtained. Our evaluation of the trials to date suggests that the definitive answer to the degree to which dietary long-chain PUFA is likely to influence visual development may only be resolved with impeccably conducted RCT.

Cloning, expression, and nutritional regulation of the mammalian Delta-6 desaturase

Arachidonic acid (20:4(n-6)) and docosahexaenoic acid (22:6(n-3)) have a variety of physiological functions that include being the major component of membrane phospholipid in brain and retina, substrates for eicosanoid production, and regulators of nuclear transcription factors. The rate-limiting step in the production of 20:4(n-6) and 22:6(n-3) is the desaturation of 18:2(n-6) and 18:3(n-3) by Delta-6 desaturase. In this report, we describe the cloning, characterization, and expression of a mammalian Delta-6 desaturase. The open reading frames for mouse and human Delta-6 desaturase each encode a 444-amino acid peptide, and the two peptides share an 87% amino acid homology. The amino acid sequence predicts that the peptide contains two membrane-spanning domains as well as a cytochrome b5-like domain that is characteristic of nonmammalian Delta-6 desaturases. Expression of the open reading frame in rat hepatocytes and Chinese hamster ovary cells instilled in these cells the ability to convert 18:2(n-6) and 18:3(n-3) to their respective products, 18:3(n-6) and 18:4(n-3). When mice were fed a diet containing 10% fat, hepatic enzymatic activity and mRNA abundance for hepatic Delta-6 desaturase in mice fed corn oil were 70 and 50% lower than in mice fed triolein. Finally, Northern analysis revealed that the brain contained an amount of Delta-6 desaturase mRNA that was several times greater than that found in other tissues including the liver, lung, heart, and skeletal muscle. The RNA abundance data indicate that prior conclusions regarding the low level of Delta-6 desaturase expression in nonhepatic tissues may need to be reevaluated.

Nutritional support of infants and children: supply and metabolism of lipids

The quantity and quality of dietary lipids and their metabolism are of major importance for the growth, body composition, development and long-term health of children, both in health and disease. Lipids are the major source of energy in early childhood and supply essential lipid-soluble vitamins and polyunsaturated fatty acids that are required in relatively high amounts during early growth. Lipids affect the composition of membrane structures, and modulate membrane functions as well as the functional development of the central nervous system. Some long-chain polyunsaturated fatty acids serve as precursors for bioactive lipid mediators, including prostaglandins, thromboxanes and leukotrienes, which are powerful regulators of numerous cell functions such as thrombocyte aggregation, inflammatory reactions and immune functions. Here we review some aspects of the biochemistry and physiology of lipids and their implications for lipoprotein metabolism, energy balance and the lipid supply during early childhood through the placenta, human milk, enteral diets and parenteral lipid emulsions.

Influence of long-chain polyunsaturated fatty acids on infant cognitive function

Long-chain polyunsaturated fatty acids (LCPUFA) are important for normal visual and cortical development. In a previous study of the effects of LCPUFA on cognitive function of term infants at the age of 3 mon, we indicated that infants with evidence of reduced growth parameters at birth and impaired attention control as manifested by a late peak fixation during infant habituation assessment may benefit from LCPUFA supplementation. The aim of this prospective study was to determine whether LCPUFA supplementation and late peak fixation are related to means-end problem-solving ability in these same infants at the age of 9 mon. Term infants (58) were randomized to one of two formulas containing either LCPUFA or no LCPUFA and completed 4 mon of feeding with their formula. Cognitive function was assessed at 3 mon of age by measures of infant habituation. Infants (20 LCPUFA and 20 no-LCPUFA) completed the problem-solving assessment at 9 mon. The no-LCPUFA group had lower scores on both measures of intention and number of solutions, but neither of these differences was significant. Analysis of covariance for the effects of group and peak fixation, covaried with gestation and birth weight, showed that the number of solutions was significantly reduced in the late peak-fixation infants receiving no LCPUFA (P<0.02). Intention scores tended to be reduced in this group (P<0.06). The late peak-fixation infants who received LCPUFA had solution and intention scores similar to early peak-fixation infants receiving LCPUFA or no LCPUFA. These findings suggest that in term infants who have reduced growth parameters at birth and who show evidence of impaired attention control, information processing and problem-solving ability in infancy may be enhanced by LCPUFA supplementation.