Dietary omega-3 fatty acid deficiency and visual loss in infant rhesus monkeys

Linolenic acid (18:3 omega 3) is a dietary precursor of docosahexaenoic acid (22:6 omega 3), the major fatty acid in the photoreceptor membranes of the retina. We hypothesized that rhesus monkeys deprived of dietary omega-3 fatty acids during prenatal and postnatal development would show plasma depletion of these fatty acids and visual impairment. Semipurified diets low in omega-3 fatty acids were fed to one group of adult female rhesus monkeys throughout pregnancy and to their infants from birth. A control group of mothers and infants received similar diets but supplying ample linolenic acid. In the plasma phospholipids of deficient infants, linolenic acid was generally undetectable and 22:6 omega 3 levels became progressively depleted, falling from 42% of control values at birth to 21% at 4 wk, 9% at 8 wk, and 6% at 12 wk of age. In the other plasma lipid classes, 22:6 omega 3 was undetectable by 12 wk. The visual acuity of the deprived infants, as measured by the preferential looking method, was reduced by one-fourth at 4 wk (P less than 0.05) and by one-half at 8 and 12 wk (P less than 0.0005) compared with control infants. These results suggest that omega-3 fatty acids may be an essential nutrient, and that 22:6 omega 3 may have a specific function in the photoreceptor membranes of the retina.

The effects of dietary alpha-linolenic acid on the composition of nerve membranes, enzymatic activity, amplitude of electrophysiological parameters, resistance to poisons and performance of learning tasks in rats

Feeding rats diets containing oils that have a low alpha-linolenic acid [18:3(n-3)] content, such as sunflower oil, results in reduced amounts of docosahexaenoic acid [22:6(n-3)] in all brain cells and organelles compared to rats fed a diet containing soybean oil or rapeseed oil. During the period of cerebral development there is a linear relationship between the n-3 fatty acid content of the brain and that of food until alpha-linolenic acid represents approximately 200 mg/100 g food [0.4% of the total dietary energy for 18:3(n-3)]. Beyond that point brain levels reach a plateau. Similar values are also found for other organs. The level of 22:6(n-3) in membranes is little affected by the dietary quantity of linoleic acid [18:2(n-6)] if 18:3(n-3) represents approximately 0.4% of energy. In membranes from rats fed diets containing sunflower oil, Na+, K(+)-ATPase activity in nerve terminals was 60%, 5'-nucleotidase in whole brain homogenate was 80%, and 2',3'-cyclic nucleotide 3'-phosphodiesterase was 88% of that in membranes from rats fed diets containing soybean oil. A diet low in alpha-linolenic acid leads to anomalies in the electroretinogram, which partially disappear with age. It has little effect on motor activity, but it seriously affects learning tasks as measured with the shuttle box test. Rats fed a diet low in alpha-linolenic acid showed an earlier mortality in response to an intraperitoneal injection of a neurotoxin, triethyltin, than did rats fed a normal soybean oil diet.

Dietary n-6 and n-3 fatty acid balance and cardiovascular health

Epidemiological and clinical studies have established that the n-6 fatty acid, linoleic acid (LA), and the n-3 fatty acids, linolenic acid (LNA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) collectively protect against coronary heart disease (CHD). LA is the major dietary fatty acid regulating low-density lipoprotein (LDL)-C metabolism by downregulating LDL-C production and enhancing its clearance. Further, the available mass of LA is a critical factor determining the hyperlipemic effects of other dietary fat components, such as saturated and trans fatty acids, as well as cholesterol. By contrast, n-3 fatty acids, especially EPA and DHA, are potent antiarryhthmic agents. EPA and DHA also improve vascular endothelial function and help lower blood pressure, platelet sensitivity, and the serum triglyceride level. The distinct functions of these two families make the balance between dietary n-6 and n-3 fatty acids an important consideration influencing cardiovascular health. Based on published literature describing practical dietary intakes, we suggest that consumption of ~6% en LA, 0.75% en LNA, and 0.25% en EPA + DHA represents adequate and achievable intakes for most healthy adults. This corresponds to an n-6/n-3 ratio of ~6:1. However, the absolute mass of essential fatty acids consumed, rather than their n-6/n-3 ratio, should be the first consideration when contemplating lifelong dietary habits affecting cardiovascular benefit from their intake.

Aluminium salts accelerate peroxidation of membrane lipids stimulated by iron salts

Aluminium salts do not themselves stimulate peroxidation of ox-brain phospholipid liposomes, but they greatly accelerate the peroxidation induced by iron(II) salts at acidic pH values. This effect of Al(III) is not seen at pH 7.4, perhaps because Al(III) salts form insoluble complexes at this pH in aqueous solution. Peroxidation of liposomes in the presence of Al(III) and Fe(II) salts is inhibited by the chelating agent desferrioxamine, and by EDTA and diethylenetriaminepentaacetic acid at concentrations greater than those of Fe(II) salt. Aluminium salts slightly stimulate the peroxidation of peroxide-depleted linolenic acid micelles, but they do not accelerate the peroxidation induced by addition of iron(II) salts to the micelles at acidic pH. Aluminium salts accelerate the peroxidation observed when human erythrocytes are treated with hydrogen peroxide at pH 7.4. Desferrioxamine decreases the peroxidation. We suggest that Al(III) ions produce an alteration in membrane structure that facilitates lipid peroxidation, and that the increased formation of fluorescent age pigments in the nervous system of patients exposed to toxic amounts of Al(III) may be related to this phenomenon. The ability of desferal to bind both iron (III) and aluminium(III) salts and to inhibit lipid peroxidation makes it an especially useful chelating agent in the treatment of 'aluminium overload'.

Dietary reference intakes for DHA and EPA

Various organizations worldwide have made dietary recommendations for eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and fish intake that are primarily for coronary disease risk reduction and triglyceride (TG) lowering. Recommendations also have been made for DHA intake for pregnant women, infants, and vegetarians/vegans. A Dietary Reference Intake (DRI), specifically, an Adequate Intake (AI), has been set for alpha-linolenic acid (ALA) by the Institute of Medicine (IOM) of The National Academies. This amount is based on an intake that supports normal growth and neural development and results in no nutrient deficiency. Although there is no DRI for EPA and DHA, the National Academies have recommended that approximately 10% of the Acceptable Macronutrient Distribution Range (AMDR) for ALA can be consumed as EPA and/or DHA. This recommendation represents current mean intake for EPA and DHA in the United States ( approximately 100mg/day), which is much lower than what many groups worldwide are currently recommending. Global recommendations for long-chain omega-3 fatty acids underscore the pressing need to establish DRIs for DHA and EPA because DRIs are recognized as the "official" standard by which federal agencies issue dietary guidance or policy directives for the health and well-being of individuals in the United States and Canada. Because of the many health benefits of DHA and EPA, it is important and timely that the National Academies establish DRIs for the individual long-chain (20 carbons or greater) omega-3 fatty acids.

High alpha-linolenic acid flaxseed (Linum usitatissimum): some nutritional properties in humans

Although high alpha-linolenic acid flaxseed (Linum usitatissimum) is one of the richest dietary sources of alpha-linolenic acid and is also a good source of soluble fibre mucilage, it is relatively unstudied in human nutrition. Healthy female volunteers consumed 50 g ground, raw flaxseed/d for 4 weeks which provided 12-13% of energy intake (24-25 g/100 g total fat). Flaxseed raised alpha-linolenic acid and long-chain n-3 fatty acids in both plasma and erythrocyte lipids, as well as raising urinary thiocyanate excretion 2.2-fold. Flaxseed also lowered serum total cholesterol by 9% and low-density-lipoprotein-cholesterol by 18%. Changes in plasma alpha-linolenic acid were equivalent when 12 g alpha-linolenic acid/d was provided as raw flaxseed flour (50 g/d) or flaxseed oil (20 g/d) suggesting high bioavailability of alpha-linolenic acid from ground flaxseed. Test meals containing 50 g carbohydrate from flaxseed or 25 g flaxseed mucilage each significantly decreased postprandial blood glucose responses by 27%. Malondialdehyde levels in muffins containing 15 g flaxseed oil or flour/kg were similar to those in wheat-flour muffins. Cyanogenic glycosides (linamarin, linustatin, neolinustatin) were highest in extracted flaxseed mucilage but were not detected in baked muffins containing 150 g flaxseed/kg. We conclude that up to 50 g high-alpha-linolenic acid flaxseed/d is palatable, safe and may be nutritionally beneficial in humans by raising n-3 fatty acids in plasma and erythrocytes and by decreasing postprandial glucose responses.

The antioxidant activity of haptoglobin towards haemoglobin-stimulated lipid peroxidation

Haemoglobin stimulates the peroxidation of lipids in two discernable phases. The first phase is inhibited by binding haemoglobin to the protein haptoglobin. The second phase is stimulated by complexable iron released from the haemoglobin molecule during the process of lipid peroxidation. This latter peroxidation is inhibitable by transferrin and the iron chelator desferrioxamine. Heat-denatured haemoglobin and haemin both stimulated lipid peroxidation but this is not inhibitable by haptoglobin. It is suggested that the haptoglobins play an important antioxidant role in vivo by preventing iron-stimulated formation of oxygen radicals.

Activation of protein kinase C by lipoxin A and other eicosanoids. Intracellular action of oxygenation products of arachidonic acid

Arachidonic acid, linolenic acid and 14 different oxygenated fatty acid derivatives were tested as activators of human protein kinase C in vitro using histone as substrate. Lipoxin A (5,6,15L-trihydroxy-7,9,11,13-eicosatetraenoic activated the kinase in the presence of calcium at 30 fold lower concentration (1 microM) than did arachidonic acid or 1,3-dioleoylglycerol. The methyl ester of lipoxin A and the free acids of leukotriene B4 as well as two lipoxin B isomers were without effect. In contrast, linolenic acid, leukotriene C4, certain mono- and dihydroxylated eicosanoids and one lipoxin B isomer had stimulatory effects, albeit at higher concentrations. The substrate specificity of protein kinase C activated by lipoxin A proved to be different from that of the phosphatidylserine or phorbol ester activated kinase. Results of the present study suggest that arachidonic acid derived oxygenation products, in particular lipoxin A, may serve as intracellular activators of protein kinase C.

Selective killing of human cancer cells by polyunsaturated fatty acids

Polyunsaturated fatty acids killed incubated human breast, lung and prostate cancer cells at concentrations which had no adverse effects on normal human fibroblasts or on normal animal cell lines. The most consistent and selective effects were obtained with fatty acids containing 3, 4 and 5 double bonds. When human cancer cells and normal human fibroblasts were co-cultured in the absence of polyunsaturated fatty acids, the malignant cells overgrew the normal ones. When eicosapentaenoic acid (EPA, 20:5n-3), gamma-linolenic acid (GLA, 18:3n-6) or arachidonic acid (AA, 20:4n-6) were added to the co-cultures, the normal cells outgrew the malignant ones. These observations suggest that treatment of malignancy with polyunsaturated fatty acids may have considerable potential while being associated with a high level of safety.

Control of polyunsaturated acids in tissue lipids

Since the discovery in 1929 that certain polyunsaturated fatty acids (PUFA) are essential for life and health, intense investigation has revealed the multiplicity of members in each of several families of PUFA, no two of which are equivalent. The quantified nutrient requirements for the essential dietary precursors of the two dominant families of PUFA have been estimated, and the general functions of these families are slowly becoming known. The PUFA are essential components of structural membrane lipids. The functions of the individual members are not yet differentiated, except as they act as precursors of synthesis of unique octadecanoid, eicosanoid, and docosanoid products of oxidation that have potent biological properties. The PUFA occur in animals and higher plants as ubiquitous and essential components of structural lipid that are in a dynamic equilibrium with the pool of dietary acyl groups. Many human diseases have been found to involve unique essential fatty acid (EFA) deficiencies or distortions of the normal equilibrium pattern. The equilibrium is influenced by the level of dietary intake or precursors, by the presence of competing essential and nonessential acyl groups, by nonoptimum intake of other essential nutrients, by hormonal effects, by drug therapy, and by other effects upon physiological condition. With the many variables already known to modulate or control the equilibrium, it should be possible with more precise understanding of each variable to shift abnormal equilibria in the direction of normalcy. This perhaps will be the next area of intensive investigation in this field of nutrition and metabolism.

Dietary n-3 (omega-3) polyunsaturated fatty acid effects on animal tumorigenesis

Environmental variables influence the incidence and expression of disease. Dietary fat is one environmental variable that has been associated experimentally and epidemiologically with alterations in certain types of tumorigenesis. Recently, detailed biochemical analyses have shown that not all fatty acid families possess the same tumor-promoting potential. In general, diets containing high levels of the n-6 polyunsaturated fatty acids have routinely enhanced tumorigenesis in lipid sensitive carcinogen-induced and tumor transplant tumor models, whereas diets with equivalent levels of n-3 polyunsaturated fatty acids have diminished tumorigenesis. At present, there is no definitive biochemical mechanism that fully explains these observations, but several possibilities have been proposed. One of the most attractive of these hypotheses is that each polyunsaturated fatty acid family has an individual effect on eicosanoid metabolism which determines its tumor-promoting potential. Regardless of current uncertainties about mechanisms of action, however, results of numerous animal models affirm the importance of qualitative, as well as quantitative, dietary lipid differences on tumorigenesis. This knowledge strengthens the probability that further advances in our understanding of lipid-tumor interrelationships will have important preventive and therapeutic medical benefits.

Essential fatty acids in the plasma phospholipids of patients with atopic eczema

We have measured all the essential fatty acids (EFA) in plasma phospholipids in forty-one adults with atopic eczema and fifty normal controls. The major dietary n-6 EFA, linoleic acid, was significantly elevated, but all its metabolites, 18:3n-6, 20:3n-6, 20:4n-6, 22:4n-6, and 22:5n-6 were significantly reduced. The major dietary n-3 EFA, alpha-linolenic acid, was also elevated, though not significantly, while all its metabolites were also significantly reduced. These observations suggest that atopic eczema is associated not with any defect of EFA intake, but with abnormal metabolism, possibly involving the enzyme delta-6-desaturase. Treatment with oral evening primrose oil produced partial correction of the n-6 EFA abnormality, but had no effect on the n-3 EFAs.

Summary of the NATO advanced research workshop on dietary omega 3 and omega 6 fatty acids: biological effects and nutritional essentiality

A number of human studies presented at the workshop indicate that the premature infant at birth is biochemically deficient in docosahexaenoic acid (DHA) in both the brain and liver phospholipids, and that DHA is essential for normal visual acuity. The amount of DHA necessary to maintain normal amounts of the liver and brain phospholipids postnatally is 11 mg/kg daily. Elderly patients on long-term gastric tube feedings and others on long-term intravenous fluids and on total parenteral nutrition are particularly prone to deficiencies of alpha-linolenic acid, eicosapentaenoic acid (EPA) and DHA. The amounts estimated to prevent deficiencies in the elderly are 800-1100 mg/d of alpha-linolenic acid and 300-400 mg/d of EPA and DHA combined. Preliminary data indicate that children with malnutrition and mucoviscidosis, women with toxemia, and elderly people have decreased amounts of DHA in plasma phospholipids. The omega 3 fatty acids lower triglycerides and, at high levels, lower cholesterol. The anti-aggregatory, anti-thrombotic and anti-inflammatory properties of omega 3 fatty acids have been confirmed, and a dose-response curve is emerging. Despite the increase in bleeding time, no clinical evidence of bleeding has been noted by the investigators in any of the studies. Clinical trials are necessary in order to precisely define the dose and mechanisms involved in defining the essentiality of omega 3 fatty acids in growth and development and their beneficial effects in coronary heart disease, hypertension, inflammation, arthritis, psoriasis, other autoimmune disorders, and cancer.

Long-term feeding of formulas high in linolenic acid and marine oil to very low birth weight infants: phospholipid fatty acids

Red blood cell (RBC) phospholipids of infants fed human milk compared with formula have more arachidonic acid (AA) and docosahexanoic acid (DHA). The addition of low levels of marine oil to infant formula with 0.6 to 2.0% alpha-linolenic acid (LLA, 18:3n-3) prevented declines in DHA in formula-fed infants; however, the feeding trials were short (4 to 6 wk), LLA concentrations were low compared with current formulas (3.0 to 5.0% LLA), and the formulas were unstable. Trials with stable formulas were necessary to determine if dietary DHA could maintain phospholipid DHA after discharge from the hospital and, in fact, if it was necessary with higher intakes of LLA. The results of acute (4 wk) and extended (to 79 wk postconception) feeding of such formulas on RBC and plasma phospholipid AA and DHA are reported here. Control formulas were identical to commercially available formulas. Experimental formulas differed only in the addition of small amounts of marine oil. DHA in RBC and plasma phosphatidylethanolamine (PE) declined during four weeks of feeding but not if marine oil provided DHA (0.2% or 0.4%) and plasma phospholipid AA (g/100 g) decreased with time and marine oil feeding. Extended feeding with marine oil accounted for half the DHA in RBC and plasma phosphatidylethanolamine at equilibrium; however, RBC (g/100 g) and plasma AA (g/100 g; mg/L plasma) decreased progressively until late infancy and were depressed further by marine oil.(ABSTRACT TRUNCATED AT 250 WORDS)

High fat diets varying in ratios of polyunsaturated to saturated fatty acid and linoleic to linolenic acid: a comparison of rat neural and red cell membrane phospholipids

The polyunsaturated-saturated (P/S) fatty acid, and linoleic-linolenic (18:2n6/18:3n3) acid ratios of diets fed to rats were varied independently during pregnancy, lactation and, in the young, for 8 d after premature weaning. The intent was to alter the proportion of membrane phospholipid fatty acids derived from 18:2n6 and 18:3n3 in the developing rat, and to compare changes in very-long-chain polyunsaturated fatty acids in membranes from the central nervous system with those of the red blood cell. All experimental diets contained 40% of energy from fat. Similar relative changes in phosphatidylethanolamine (PE) and phosphatidylcholine (PC) fatty acid pattern occurred in both neural and red blood cell membranes when dietary 18:2n6/18:3n3 was increased from 7 to 240. Docosapentaenoate (22:5n6) from 18:2n6 increased, and docosapentaenoate (22:5n3) and docosahexaenoate (22:6n3) from 18:3n3 decreased in both types of membranes. On the other hand, P/S ratios of 0.3 and 1.6 at a constant ratio of 18:2n6/18:3n3 produced identical membrane phospholipid fatty acid patterns. Both red blood cell and neural membranes show the same relative effects of modification of dietary lipids on the composition of very-long-chain polyunsaturated fatty acids.

Effects of long-chain, saturated fatty acids on membrane microviscosity and adrenocorticotropin responsiveness of human adrenocortical cells in vitro

Adrenoleukodystrophy (ALD) and adrenomyeloneuropathy are inherited disorders in which long-chain, saturated fatty acids (LCFA) accumulate in various tissues. A mechanism by which LCFA cause the endocrine and neurological dysfunction characteristic of these diseases is proposed based on in vitro response of human adrenocortical cells to ACTH in the presence of various fatty acids. Human adrenocortical cells cultured in the presence of 5 microM hexacosanoic (C26:0) or lignoceric (C24:0) acids showed decreased basal and ACTH-stimulated cortisol release compared with cells cultured without exogenous fatty acids or in the presence of linoleic acid (C18:2). Measurement of fluorescence polarization demonstrates a significant increase in the membrane microviscosity of cells cultured in the presence of LCFA. It is hypothesized that cells exposed to LCFA have increased membrane microviscosity with a consequent decrease in their ability to respond to ACTH. This decrease in trophic support may contribute to the adrenal insufficiency and atrophy in patients with ALD.

Brain cell and tissue recovery in rats made deficient in n-3 fatty acids by alteration of dietary fat

Rats were fed a purified diet containing either 1.5% sunflower oil [940 mg linoleic acid [18:2(n-6)]/100 g diet; 6 mg alpha-linolenic acid [18:3(n-3)]/300 g diet] or 1.9% soybean oil [940 mg 18:2(n-6)/100 g diet; 130 mg 18:3(n-3)/100 g diet]. In all cases and tissues examined 22:6(n-3) was lower and 22:5(n-6) was higher in rats fed sunflower oil than in rats fed soybean oil. Levels of 22:4(n-6) and 20:4(n-6) were largely unaffected. Expressed as a percentage of that in soybean oil-fed rats, 22:6(n-3) in sunflower oil-fed rats was as follows: neurons, 49; astrocytes, 47; oligodendrocytes, 10; lung, 27; testes, 32; retina, 36; liver, 35 and kidneys, 45. Ten wk after the change in diet of 60-d-old rats from one containing sunflower oil to one containing soybean oil, the fatty acid composition of the brain cells had not reached control values, e.g., that obtained in animals continuously fed soybean oil; 22:6(n-3) was 77, 65 and 80% of control levels for astrocytes, oligodendrocytes and neurons, respectively. In contrast, the recovery measured by the decay of 22:5(n-6) was complete within 10 wk. For 22:6(n-3), it took approximately 2 wk for liver and kidney to recover to the control value, 3 wk for lung, 6 wk for retina and 10 wk for testes. The decrease of 22:5(n-6) was rapid: the control values were reached within 2 wk for kidney, liver and lung and within 6 wk for retina.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of grass and legume silages for milk production. 2. In vivo and in sacco evaluations of rumen function

Two experiments were conducted to investigate the basis for higher voluntary intakes and increased alpha-linolenic acid content in milk from cows offered clover silages. Six cows with rumen and duodenal cannulae were used in a four-period changeover-design experiment. Cows received 8 kg/d of dairy concentrate and had ad libitum access to one of six silage treatments: grass, red clover, white clover, alfalfa, and 50/50 (dry matter basis) mixtures of grass with red clover or white clover. The rumen fermentability of grass, red clover, white clover, and grass/red clover silages was also evaluated in a nylon bag study. Legume silages led to increased dry matter intake and milk production in comparison with grass silage. There was no significant effect of legume silages on rumen pH and volatile fatty acid concentrations, but a significant increase in rumen ammonia concentration with the legume silages, reflecting their higher protein content. The inclusion of white clover or alfalfa silage, but not red clover silage, in diets led to an increase in molar proportions of isobutyric, iso-valeric, and n-valeric acids in comparison with diets based on grass silage. Rumen fill was significantly lower, and rumen passage rates were significantly higher for cows offered alfalfa or white clover silages. However, the markedly different particle size distribution of rumen contents with these feeds suggests very different mechanisms for the high intake characteristics: high rates of particle breakdown and passage with alfalfa, and high rates of fermentation and passage with white clover. Microbial energetic efficiency (grams microbial N per kilogram organic matter apparently digested in the rumen) was highest for cows offered alfalfa silage, intermediate for clover silage, and lowest for cows offered grass silage. These differences reflect the higher rumen outflow rates for legume silages in comparison with grass silage. However, the effect of these differences on N-use efficiency (feed to milk) was probably quite small in comparison with effects of N intake. Although the biohydrogenation of alpha-linolenic acid was still high for red clover silage (86.1% compared with 94.3% for grass silage), there was a 240% increase in the proportion of alpha-linolenic acid passing through the rumen. This explains the increased recovery of alpha-linolenic acid from feed into milk with diets based on red clover silage.

Determination of the optimal ratio of linoleic acid to alpha-linolenic acid in infant formulas

The fatty acid composition of erythrocyte total lipids taken from a group of term infants 10 weeks after being fed a commercial infant formula with a high ratio of linoleic acid (18:2n-6) (LA) to alpha-linolenic acid (18:3n-3) (ALA) (19:1; LA, 14%; ALA, 0.7%; group A, n = 10) was compared with the fatty acid composition of erythrocytes from infants fed formulas that contained LA/ALA ratios reduced by either increasing ALA (4:1; LA, 13%; ALA, 3.3%; group B, n = 11) or decreasing LA (3:1; LA, 3.5%; ALA, 1.1%; group C, n = 8). Results were compared with those in an age-controlled group (n = 9) of breast-fed infants. Decreasing the LA/ALA ratio increased n-3 C20 and C22 fatty acid incorporation (formula B = 8.98% +/- 0.65%; formula C = 9.30% +/- 0.95%) relative to formula A (5.97% +/- 0.76%; p less than 0.05). Although docosahexaenoic acid (22:6n-3) (DHA) incorporation was highest in infants fed formulas B and C (4.78% +/- 0.45% and 4.48% +/- 0.49%, respectively) relative to formula A (3.47% +/- 0.46%; p less than 0.05), it did not reach levels found in breast-fed infants (6.55% +/- 1.23%; p less than 0.05). In addition, levels of arachidonic acid (20:4n-6) (AA) were lower in all formula-fed groups (p less than 0.05) relative to those in breast-fed infants. Based on some equations, it is predicted that AA levels in tissues of infants fed lower LA/ALA ratios would be reduced even further. Because both AA and DHA are probably essential for normal neural development of the infant, formulas with LA/ALA ratios below 4:1 are likely to result in fatty acid profiles notably different from those of breast-fed infants.

Essentiality of dietary omega 3 fatty acids for premature infants: plasma and red blood cell fatty acid composition

Pre-term infants, that are not breast-fed, are deprived of vital intrauterine fat accretion during late pregnancy and must rely on formula to obtain fatty acids essential for normal development, particularly of the visual system. Preterm infants (30 wk postconception) receiving human milk were compared to infants given one of the following formulae: Formula A was a commercial preterm formula with predominantly 18:2 omega 6 (24.2%) and low (0.5%) 18:3 omega 3; Formula B was based on soy oil and contained similar 18:2 omega 6 levels (20%) and high 18:3 omega 3 (2.7%); Formula C was also a soy oil-based formula (20% 18:2, 1.4% 18:3) but was supplemented with marine oil to provide omega 3 long-chain polyunsaturated fatty acids (LCP) at a level (docosahexaenoic acid, DHA, 0.35%) equivalent to human milk. At entry (10 days of age), the fatty acid composition of plasma and red blood cell (RBC) membrane lipids of the formula groups were identical. By 36 wk postconception, the DHA content in lipids of group A was significantly reduced compared to that in the human milk and marine oil formula groups. Omega-3 LCP results were further amplified by 57 wk with compensatory increases in 22:5 omega 6 in both plasma and RBC lipids. Provision of 2.7% alpha-linolenic acid in formula group B was sufficient to maintain 22:6 omega 3 levels equivalent to those in human milk-fed infants at 36 wk but not at 57 wk. Effects on the production of thiobarbituric acid reactive substances and fragility of RBC attributable to the marine oil supplementation were negligible. The results support the essentiality of omega 3 fatty acids for preterm infants to obtain fatty acid profiles comparable to infants receiving human milk. Formula for preterm infants should be supplemented with omega 3 fatty acids including LCP.