Composition of phospholipid fatty acids in red blood cell membranes of patients in intensive care units: effects of different intakes of soybean oil, medium-chain triglycerides, and black-currant seed oil

Docosahexaenoate-enriched fish oil and medium chain triglycerides shape the feline plasma lipidome and synergistically decrease circulating gut microbiome-derived putrefactive postbiotics

The purpose of this study was to examine the influence of medium-chain fatty acid-containing triglycerides (MCT), long-chain polyunsaturated fatty acid-containing triglycerides, and their combination on the plasma metabolome of cats (Felis catus), including circulating microbiome-derived postbiotics. After a 14-day lead-in on the control food, cats were randomized to one of four foods (control, with 6.9% MCT, with fish oil [FO; 0.14% eicosapentaenoate, 1.0% docosahexaenoate], or with FO+MCT; n = 16 per group) for 28 days. Analysis of plasma metabolites showed that the addition of FO and MCT led to synergistic effects not seen with either alone across a number of lipid classes, including fatty acids, acylcarnitines, and acylated amines including endocannabinoids. Notably, the FO+MCT group had an increase in ketone body production relative to baseline and beyond that seen with MCT alone. N-acyl taurines, the accumulation of which has been implicated in the onset of type 2 diabetes, were significantly decreased in the FO+MCT group. Significant decreases in the gut microbiome-derived postbiotic classes of indoles/indolic sulfates and phenols/phenolic sulfates were observed only the FO+MCT group. Overall, the combination of MCT and FO led to number of changes in plasma metabolites that were not observed with either oil alone, particularly in postbiotics.

Gas chromatography-mass spectrometry-based analytical strategies for fatty acid analysis in biological samples

Fatty acids play critical roles in biological systems. Imbalances in fatty acids are related to a variety of diseases, which makes the measurement of fatty acids in biological samples important. Many analytical strategies have been developed to investigate fatty acids in various biological samples. Due to the structural diversity of fatty acids, many factors need to be considered when developing analytical methods including extraction methods, derivatization methods, column selections, and internal standard selections. This review focused on gas chromatography-mass spectrometry (GC-MS)-based methods. We reviewed several commonly used fatty acid extraction approaches, including liquid-liquid extraction and solid-phase microextraction. Moreover, both acid and base derivatization methods and other specially designed methods were comprehensively reviewed, and their strengths and limitations were discussed. Having good separation efficiency is essential to building an accurate and reliable GC-MS platform for fatty acid analysis. We reviewed the separation performance of different columns and discussed the application of multidimensional GC for improving separations. The selection of internal standards was also discussed. In the final section, we introduced several biomedical studies that measured fatty acid levels in different sample matrices and provided hints on the relationships between fatty acid imbalances and diseases.

Clinical Sequelae From Overfeeding in Enterally Fed Critically Ill Adults: Where Is the Evidence?

Enteral energy delivery above requirements (overfeeding) is believed to cause adverse effects during critical illness, but the literature supporting this is limited. We aimed to quantify the reported frequency and clinical sequelae of energy overfeeding with enterally delivered nutrition in critically ill adult patients. A systematic search of MEDLINE, EMBASE, and CINAHL from conception to November 28, 2018, identified clinical studies of nutrition interventions in enterally fed critically ill adults that reported overfeeding in 1 or more study arms. Overfeeding was defined as energy delivery > 2000 kcal/d, > 25 kcal/kg/d, or ≥ 110% of energy prescription. Data were extracted on methodology, demographics, prescribed and delivered nutrition, clinical variables, and predefined outcomes. Cochrane "Risk of Bias" tool was used to assess the quality of randomized controlled trials (RCTs). Eighteen studies were included, of which 10 were randomized (n = 4386 patients) and 8 were nonrandomized (n = 223). Only 4 studies reported a separation in energy delivery between treatment groups whereby 1 arm met the definition of overfeeding, which reported no between-group differences in mortality, infectious complications, or ventilatory support. Overfeeding was associated with increased insulin administration (median 3 [interquartile range: 0-41.8] vs 0 [0-30.6] units/d) and upper-gastrointestinal intolerance in 1 large RCT and with duration of antimicrobial therapy in a small RCT. There are limited high-quality data to determine the impact of energy overfeeding of critically ill patients by the enteral route; however, based on available evidence, overfeeding does not appear to affect mortality or other important clinical outcomes.

Dietary omega-3 PUFA and health: stearidonic acid-containing seed oils as effective and sustainable alternatives to traditional marine oils

The daily consumption of dietary omega-3 PUFA is recommended by governmental agencies in several countries and by a number of health organizations. The molecular mechanisms by which these dietary PUFA affect health involve the enrichment of cellular membranes with long-chain 20- and 22-carbon omega-3 PUFA that impacts tissues by altering membrane protein functions, cell signaling, and gene expression profiles. These changes are recognized to have health benefits in humans, especially relating to cardiovascular outcomes. Cellular membrane enrichment and health benefits are associated with the consumption of long-chain omega-3 PUFA found in marine oils, but are not generally linked with the consumption of alpha-linolenic acid, the 18-carbon omega-3 PUFA found in plant seed oils. However, the supply of omega-3 PUFA from marine sources is limited and may not be sustainable. New plant-derived sources of omega-3 PUFA like stearidonic acid-soy oil from genetically modified soybeans and Ahiflower oil from Buglossoides arvensis seeds that are enriched in the 18-carbon omega-3 PUFA stearidonic acid are being developed and show promise to become effective as well as sustainable sources of omega-3 PUFA. An example of changes in tissue lipid profiles associated with the consumption of Ahiflower oil is presented in a mouse feeding study.

Effects of duration of treatment and dosage of eicosapentaenoic acid and stearidonic acid on red blood cell eicosapentaenoic acid content

OBJECTIVE

The purpose of this randomized, controlled, parallel group study was to characterize the relationships between dosages of stearidonic acid (SDA) and eicosapentaenoic acid (EPA), and incorporation of EPA into red blood cell (RBC) membranes over time.

METHODS

Healthy subjects (n=131) received capsules with placebo (safflower oil), SDA (0.43, 1.3, 2.6, or 5.2 g/d) or EPA (0.44, 1.3, or 2.7 g/d) for 12 weeks. RBC fatty acids were analyzed biweekly.

RESULTS

RBC %EPA increased in all EPA and SDA groups (p<0.02 vs. control) except the 0.43 g/d SDA group (p=0.187). For theoretical intakes of EPA of 0.25, 0.5, and 0.89 g/d, the amounts of SDA needed to achieve equivalent RBC EPA enrichment were 0.61, 1.89, and 5.32 g/d (conversion efficiencies of 41%, 26%, and 17%), respectively.

CONCLUSIONS

SDA increased RBC %EPA in a dosage and time-dependent manner at intakes as low as 1.3 g/d.

Chemistry behind Vegetarianism

This review summarizes the effect of a habitual vegetarian diet on clinical complications in relation to chemistry and biochemistry. Omnivores have a significantly higher cluster of cardiovascular risk factors compared with vegetarians, including increased body mass index, waist to hip ratio, blood pressure, plasma total cholesterol (TC), triacylglycerol and LDL-C levels, serum lipoprotein(a) concentration, plasma factor VII activity, ratios of TC/HDL-C, LDL-C/HDL-C and TAG/HDL-C, and serum ferritin levels. Compared with omnivores, vegetarians, especially vegans, have lower serum vitamin B₁₂ concentration and n-3 polyunsaturated fatty acid (PUFA) levels in the tissue membrane phospholipids, which are associated with increased collagen and ADP stimulated ex vivo whole blood platelet aggregation, plasma 11-dehydrothromboxane B₂, and homocysteine levels and decreased plasma HDL-C. This may be associated with an increased thrombotic and atherosclerotic risk. It is suggested that vegetarians, especially vegans, should increase their dietary n-3 PUFA and vitamin B₁₂ intakes.

Dietary intake of stearidonic acid-enriched soybean oil increases the omega-3 index: randomized, double-blind clinical study of efficacy and safety

BACKGROUND

The benefits of omega-3 (n-3) long-chain polyunsaturated fatty acids to heart health are well established. Stearidonic acid (SDA, 18:4n-3) may contribute to these benefits.

OBJECTIVE

The objective was to evaluate the ability of SDA-containing soybean oil to increase the omega-3 index [erythrocyte eicosapentaenoic acid (EPA) + docosahexaenoic acid, as a percentage of total fatty acids] and to affect other cardiovascular disease risk markers compared with EPA and regular soy oil (control).

DESIGN

This was a randomized, placebo-controlled, double-blind multicenter study in which 252 overweight subjects were randomly assigned to 1 of 3 treatments for 12 wk: 1 g encapsulated soybean oil/d plus 14.7 g liquid soybean oil/d to be mixed in food (control group), 1 g encapsulated EPA/d plus 14.7 g liquid soybean oil/d (EPA group), and 1 g encapsulated soybean oil/d plus 14.7 g liquid SDA-enriched soybean oil/d, providing 4.2 g SDA (SDA group). Subjects consumed treatment oils in exchange for other oils in their diet.

RESULTS

The mean (±SE) baseline omega-3 index was similar between treatments, but after 12 wk of treatment values for this index were 4.15 ± 0.12%, 4.84 ± 0.13%, and 4.69 ± 0.15% for control, EPA, and SDA groups, respectively. Values for the EPA and SDA groups were greater than those for control subjects in the intent-to-treat population (P < 0.001 and P = 0.006, respectively). No adverse treatment-related effects of SDA-enriched soybean oil were reported.

CONCLUSIONS

SDA-enriched soybean oil increased the omega-3 index by raising erythrocyte EPA concentrations. SDA-enriched soybean oil is a land-based n-3 fatty acid that is a sustainable approach to increasing tissue concentrations of long-chain polyunsaturated n-3 fatty acids.

Long-chain conversion of [13C]linoleic acid and α-linolenic acid in response to marked changes in their dietary intake in men

We studied the long-chain conversion of [U-13C]alpha-linolenic acid (ALA) and linoleic acid (LA) and responses of erythrocyte phospholipid composition to variation in the dietary ratios of 18:3n-3 (ALA) and 18:2n-6 (LA) for 12 weeks in 38 moderately hyperlipidemic men. Diets were enriched with either flaxseed oil (FXO; 17 g/day ALA, n=21) or sunflower oil (SO; 17 g/day LA, n=17). The FXO diet induced increases in phospholipid ALA (>3-fold), 20:5n-3 [eicosapentaenoic acid (EPA), >2-fold], and 22:5n-3 [docosapentaenoic acid (DPA), 50%] but no change in 22:6n-3 [docosahexanoic acid (DHA)], LA, or 20:4n-6 [arachidonic acid (AA)]. The increases in EPA and DPA but not DHA were similar to those in subjects given the SO diet enriched with 3 g of EPA plus DHA from fish oil (n=19). The SO diet induced a small increase in LA but no change in AA. Long-chain conversion of [U-13C]ALA and [U-13C]LA, calculated from peak plasma 13C concentrations after simple modeling for tracer dilution in subsets from the FXO (n=6) and SO (n=5) diets, was similar but low for the two tracers (i.e., AA, 0.2%; EPA, 0.3%; and DPA, 0.02%) and varied directly with precursor concentrations and inversely with concentrations of fatty acids of the alternative series. [13C]DHA formation was very low (<0.01%) with no dietary influences.

Plasma and neutrophil fatty acid composition in advanced cancer patients and response to fish oil supplementation

Metabolic demand and altered supply of essential nutrients is poorly characterised in patients with advanced cancer. A possible imbalance or deficiency of essential fatty acids is suggested by reported beneficial effects of fish oil supplementation. To assess fatty acid status (composition of plasma and neutrophil phospholipids) in advanced cancer patients before and after 14 days of supplementation (12+/-1 g day(-1)) with fish (eicosapentaenoic acid, and docosahexaenoic acid) or placebo (olive) oil. Blood was drawn from cancer patients experiencing weight loss of >5% body weight (n=23). Fatty acid composition of plasma phospholipids and the major phospholipid classes of isolated neutrophils were determined using gas liquid chromatography. At baseline, patients with advanced cancer exhibited low levels (<30% of normal values) of plasma phospholipids and constituent fatty acids and elevated 20 : 4 n-6 content in neutrophil phospholipids. High n-6/n-3 fatty acid ratios in neutrophil and plasma phospholipids were inversely related to body mass index. Fish oil supplementation raised eicosapentaenoic acid and docosahexaenoic acid content in plasma but not neutrophil phospholipids. 20 : 4 n-6 content was reduced in neutrophil PI following supplementation with fish oil. Change in body weight during the supplementation period related directly to increases in eicosapentaenoic acid in plasma. Advanced cancer patients have alterations in lipid metabolism potentially due to nutritional status and/or chemotherapy. Potential obstacles in fatty acid utilisation must be addressed in future trials aiming to improve outcomes using nutritional intervention with fish oils.

Fatty acid content of plasma lipids and erythrocyte phospholipids are altered following burn injury

The objective of this study was to examine compositional and quantitative changes in fatty acids of plasma components and red blood cell phospholipids (PL) immediately following and during recovery from burn injury. Subjects (n = 10) with >10% total body surface area burn had blood drawn at specific timepoints (0 to >50 d) following burn injury. Fatty acid composition of red blood cell PL and plasma PL, cholesteryl esters (CE), and triglycerides was determined using gas-liquid chromatography after separating each fraction from extracted lipids by thin-layer chromatography. Total plasma PL and CE in burn patients were lower than in healthy control subjects with reduced 20:4n-6, n-6, and n-3 fatty acids and higher levels of monounsaturated and saturated fatty acids early after burn. CE levels remained half that of healthy control values up to 50 d post-burn. Red blood cell PL had decreased 20:4n-6 content and profiles similar to that of an essential fatty acid deficiency early after burn. These results suggest an impairment in lipoprotein and polyunsaturated fatty acid metabolism in the early post-burn period. Lower levels of 20:4n-6 and n-3 fatty acids in every plasma fraction suggest increased use of these fatty acids for wound healing and immune function following burn injury. Further work is needed to determine the ability of burn patients to utilize essential fatty acids in order to design nutritional intervention that promotes wound healing and immunological functions consistent with recovery in these patients.

Effect of dietary alpha-linolenic acid on thrombotic risk factors in vegetarian men

BACKGROUND

Vegetarians have lower platelet and plasma concentrations of n-3 polyunsaturated fatty acids (PUFAs) than do omnivores. We recently showed that male vegetarians have higher platelet aggregability than do omnivores.

OBJECTIVE

We investigated whether male vegetarians (n = 17) who consumed an increased amount of dietary alpha-linolenic acid (ALA) showed any changes in their tissue profile of PUFAs, plasma thromboxane concentrations, platelet aggregability, or hemostatic factors.

DESIGN

During the study, all subjects maintained their habitual vegetarian diets except that a proportion of dietary fat was replaced with vegetable oils and margarines that were provided. Initially, all subjects consumed a low-ALA diet (containing safflower oil and safflower oil-based margarine) for 14 d; they then consumed either a moderate-ALA diet (containing canola oil and canola oil-based margarine) or a high-ALA diet (containing linseed oil and linseed oil-based margarine) for 28 d. Blood samples were collected at day 0 (baseline), day 14, and day 42.

RESULTS

Eicosapentaenoic acid, docosapentaenoic acid, total n-3 PUFAs, and the ratio of n-3 to n-6 PUFAs were significantly increased (P < 0.05), whereas the ratio of arachidonic acid to eicosapentaenoic acid was decreased (P < 0.05), in platelet phospholipids, plasma phospholipids, and triacylglycerols after either the moderate-ALA or high-ALA diet compared with the low-ALA diet. No significant differences were observed in thrombotic risk factors.

CONCLUSION

ALA from vegetable oils (canola and linseed) has a beneficial effect on n-3 PUFA concentrations of platelet phospholipids and plasma lipids in vegetarian males.

Relationship between plasma insulin and erythrocyte fatty acid composition

Insulin resistance is an important condition which underlies much of the coronary artery disease in affluent societies. We have related insulin resistance, as assessed by fasting plasma insulin, to erythrocyte membrane composition in 54 healthy men and women on a low fat diet. We found a inverse relationship (r = -0.41, P = 0.002) between fasting plasma insulin and the percentage of arachidonic acid in erythrocyte fatty acids. An inverse relationship of similar strength was found with total n-6 fatty acids and a positive relationship was found with the percentage of saturated fatty acids (r = 0.39, P < 0.01). No relationship was found with n-3 fatty acids. We would suggest that n-6 fatty acids, and in particular arachidonic acid, modify the membrane environment of the insulin receptor (or the glucose transporters) so that lower levels of insulin are required for glucose homeostasis.

Accelerated nitrogen loss after traumatic injury is not attenuated by achievement of energy balance

BACKGROUND

We wanted to determine if achievement of energy balance decreases myofibrillar protein catabolism and nitrogen loss during posttraumatic catabolic illness.

METHODS

Surgical intensive care unit of a level I trauma center in a university medical center. Trauma patients expected to be mechanically ventilated for at least 4 days were randomly assigned to one of three parenteral feeding groups: (1) nonprotein calorie group: dextrose and lipid intake equal to measured energy expenditure; (2) total calorie group: dextrose, lipid, and protein intake equal to measured energy expenditure; and (3) hypocaloric group: dextrose and lipid intake equal to 50% of measured energy expenditure. Target protein intake for all groups was 1.7 g/kg body wt. On day 4 of nutrition support, a 24-hour balance study was conducted. Urine urea and total nitrogen production, 3-methylhistidine excretion, energy expenditure, and substrate utilization were measured.

RESULTS

Despite significant differences in nonprotein and total calorie balance among the groups, nitrogen loss, nitrogen balance, and catabolic rate were not significantly different. Nitrogen loss correlated with catabolic rate but not with energy expenditure or energy balance. Catabolic rate was associated with energy expenditure but not with energy balance. Nitrogen loss was positively correlated with the percentage of nonprotein energy expenditure met by nonprotein calorie intake.

CONCLUSIONS

Achievement of energy balance (nonprotein or total energy) failed to decrease catabolic rate or nitrogen loss acutely in multiple trauma patients. Provision of caloric intake equal to energy expenditure does not seem necessary during the acute phase of posttraumatic catabolic illness.

gamma-Linolenic acid-containing diet attenuates bleomycin-induced lung fibrosis in hamsters

Although bleomycin (BLM), an antineoplastic drug, is used in the treatment of a variety of tumors, the mechanism(s) that contribute to its induced lung injury and fibrosis are not fully elucidated. Since alterations in the levels of certain fatty acid metabolites have been associated with BLM-induced lung injury, we tested the effects of dietary gamma-linolenic acid (GLA)-containing evening primrose oil on BLM-induced morphological alterations in the hamster lung, the marked elevation of tissue hydroxyproline (a marker for collagen synthesis), and elevated generation of arachidonic acid metabolites (marker of inflammatory mediators). Our data revealed that after 14 d of dietary GLA-containing oil (i) BLM-induced elevation of lung hydroxyproline was suppressed (P < 0.05), (ii) the marked BLM-induced elevation of lung leukotriene B4 (LTB4) (a marker of polymorphanuclear generation of proinflammatory LTB4) was significantly suppressed (P < 0.05). The decrease in LTB4 was accompanied by marked elevations (P < 0.05) of lung prostaglandin E1 (PGE1) and 15-hydroxyeicosatrienoic acid (15-HETrE), both with known antiinflammatory properties. Taken together, data from these studies suggest that dietary GLA-containing oil contributes to tissue elevation of PGE1 and 15-HETrE, which in vivo may attenuate lung inflammation and fibrosis.

Cyclic vs continuous enteral feeding with omega-3 and gamma-linolenic fatty acids: effects on modulation of phospholipid fatty acids in rat lung and liver immune cells

Arachidonic acid (AA) present in lung and liver immune cell phospholipids is the precursor of eicosanoids that promote neutrophil margination, leading to tissue injury and inflammation. Administration of novel enteral formulations low in linoleic acid (LA) and containing eicosapentaenoic acid (EPA) from fish oil and gamma-linolenic acid (GLA) from borage oil displaces AA and promotes cell formation of eicosanoids with reduced inflammatory potential. The present study was undertaken to determine whether or not short-term provision of enteral diets containing GLA, EPA, or both in a cyclic fashion modulated the fatty acid composition of rat alveolar macrophage (AM) and liver Kupffer and endothelial (K&E) cell phospholipids in vivo to the extent achieved during continuous feeding.

METHODS

Rats were isocalorically fed through a gastrostomy catheter for 3 or 6 days with high-fat, low-carbohydrate diets that were enriched with either LA (diet A), EPA (diet B), or EPA + GLA (diet C). The rats were randomized by infusion modality, ie, continuous vs cyclic (14 hours feeding with 10 hours fasting daily) feeding. AM and K&E were isolated and phospholipid fatty acid profiles were determined by gas chromatography.

RESULTS

The dietary effects on AM and K&E cell phospholipid fatty acids for a given feeding period were not significantly influenced by the infusion modality. AM and K&E cells from rats receiving either diet B or diet C for 3 days had significantly lower AA and LA and higher EPA and dihomo-GLA (DHGLA), respectively, than rats given diet A regardless of the infusion modality. The mole % of EPA and DHGLA in K&E cells were higher after 6 vs 3 days of cyclic feeding with diet C. Using the eicosanoid precursor ratio (EPA + DHGLA/AA), the potential for generation of AA-derived eicosanoids was lower in rats given die B or C vs diet A regardless of infusion modality.

DISCUSSION

Given the rapid changes in lung and liver immune cell phospholipid fatty acids, short-term provision of EPA and GLA-enriched diets cyclically or continuously may prove clinically relevant for modulating the fatty acid composition and potential eicosanoid formation by these cells.

Inhibition of neutrophil respiratory burst and cytokine priming by gamma-linolenic acid

The effect of n-6 fatty acids, particularly gamma-linolenic acid (GLA), on the oxidase response and neutrophil priming by tumour necrosis factor alpha and interleukin 8 was studied in both normal volunteers and patients with obstructive jaundice. GLA inhibited the neutrophil respiratory burst at concentrations higher than 50 mummol/l, but abolished cytokine priming at concentrations as low as 1 mummol/l. Inhibition was not the result of either cytotoxicity to the neutrophils or alteration in cytosolic free calcium homoeostasis. It is concluded that GLA is a potential inhibitor of neutrophil priming by cytokines and of the oxidative response.

Dietary linoleic acid influences desaturation and acylation of deuterium-labeled linoleic and linolenic acids in young adult males

The purpose of this study was to investigate the effect of dietary linoleic acid (18:2(n - 6)) on the conversion of 18:2(n - 6) and 18:3(n - 3) to their respective n - 6 and n - 3 metabolites; to compare the incorporation of these fatty acids into human plasma lipids; to evaluate the importance of dietary 18:3(n - 3) as a precursor for the biosynthesis of long-chain length n - 3 fatty acids. The approach used was to feed young adult male subjects (n = 7) diets containing 2 levels of linoleic acid (SAT diet, 15 g/day; PUFA diet, 30 g/day) for 12 days. A mixture of triacylglycerols containing deuterated linolenic (18:3(n - 3)) and linoleic (18:2(n - 6)) acids was fed and blood samples were drawn over a 48 h period. Concentrations of deuterated 18:3(n - 3) in plasma total lipid ranged from 309.2 to 606.4 microgram/ml and concentrations of 18:2(n - 6) ranged from 949.2 to 1743.3 micrograms/ml. The sum of the deuterated n - 3 long-chain length fatty acid metabolites in plasma total lipid were 116 +/- 4.3 micrograms/ml (SAT diet) and 41.6 +/- 12.4 micrograms/ml (PUFA diet). The total deuterated n - 6 fatty acid metabolites were 34.6 +/- 12.2 micrograms/ml (SAT diet) and 9.8 +/- 5.9 micrograms/ml (PUFA diet). The total percent conversion of deuterated 18:3(n - 3) to n - 3 fatty acid metabolites and deuterated 18:2(n - 6) to n - 6 fatty acid metabolites were 11-18.5% and 1.0-2.2%, respectively. The percentages for deuterated 20:5(n - 3), 22:5(n - 3) and 22:6(n - 3) (6.0%, 3.5%, and 3.8%) were much higher than for 20:3(n - 6) and 20:4(n - 6) (0.9% and 0.5%). Overall, conversion of deuterated 18:3(n - 3) and 18:2(n - 6) was reduced by 40-54% when dietary intake of 18:2(n - 6) was increased from 15 to 30 g/day. Comparison of the deuterated 18:3(n - 3) and 18:2(n - 6) data for plasma triacylglycerol and phosphatidylcholine (PC) indicated that 18:2(n - 6) was preferentially incorporated into PC. Dietary 18:2(n - 6) intake did not alter acyltransferase selectivity but activity was reduced when 18:2(n - 6) intake was increased. Based on these results, conversion of the 18:3(n - 3) in the US diet (2 g) is estimated to provide 75-85% of the long-chain length n - 3 fatty acids needed to meet daily requirements for some (but not all) adults.