Dietary menhaden, seal, and corn oils differentially affect lipid and Ex vivo eicosanoid and thiobarbituric acid-reactive substances generation in the guinea pig

This investigation was carried out to characterize the effects of specific dietary marine oils on tissue and plasma fatty acids and their capacity to generate metabolites (prostanoids, lipid peroxides). Young male guinea pigs were fed nonpurified diet (NP), or NP supplemented (10%, w/w) with menhaden fish oil (MO), harp seal oil (SLO), or corn oil (CO, control diet) for 23 to 28 d. Only the plasma showed significant n−3 polyunsaturated fatty acid (PUFA)-induced reductions in triacylglycerol (TAG) or total cholesterol concentration. Proportions of total n−3 PUFA in organs and plasma were elevated significantly in both MO and SLO dietary groups (relative to CO), and in all TAG fractions levels were significantly higher in MO-than SLO-fed animals. The two marine oil groups differed in their patterns of incorporation of eicosapentaenoic acid (EPA). In guinea pigs fed MO, the highest levels of EPA were in the plasma TAG, whereas in SLO-fed animals, maximal incorporation of EPA was in the heart polar lipids (PL). In both marine oil groups, the greatest increases in both docosahexaenoic acid (22∶6n−3, DHA) and docosapentaenoic acid (22∶5n−3, DPA) relative to the CO group, were in plasma TAG, although the highest proportions of DHA and DPA were in liver PL and heart TAG, respectively. In comparing the MO and SLO groups, the greatest difference in levels of DHA was in heart TAG (MO>SLO, P<0.005), and in levels of DPA was in heart PL (SLO>MO, P<0.0001). The only significant reduction in proportions of the major n−6 PUFA, arachidonic acid (AA), was in the heart PL of the SLO group (SLO>MO=CO, P<0.005). Marine oil feeding altered ex vivo generation of several prostanoid metabolites of AA, significantly decreasing thromboxane A₂ synthesis in homogenates of hearts and livers of guinea pigs fed MO and SLO, respectively (P<0.04 for both, relative to CO). Lipid peroxides were elevated to similar levels in MO- and SLO-fed animals in plasma, liver, and adipose tissue, but not in heart preparations. This study has shown that guinea pigs respond to dietary marine oils with increased organ and plasma n−3 PUFA, and changes in potential synthesis of metabolites. They also appear to respond to n−3 PUFA-enriched diets in a manner that is different from that of rats.     

Enrichment of eicosapentaenoic acid and docosahexaenoic acid in saponified menhaden oil

Eicosapentaenoic acid (EPA, 20∶5n−3) and docosahexaenoic acid (DHA, 22∶6n−3) in free fatty acids (FFA) derived from saponified menhaden oil were concentrated by the solubility differences of FFA-salts in organic solvent. FFA-salts were formed by adding NaOH to a solution containing FFA. A Buchner funnel was used to separate solid phases from liquids containing FFA-salts. FFA that are rich in EPA and DHA can be recovered from the liquid phase by the addition of 12 N HCl. The effects of reaction time, the amount of NaOH, and solvent used on the concentration of EPA and DHA were systematically investigated. With a total volume of 112 mL, made up of 1.85% 15 N NaOH, 88.1% acetone, and 10.0% FFA, a reaction temperature of 30°C, and a reaction time of 1 h, the resulting liquid phase contained 65.4 wt% EPA and DHA, with a corresponding yield of 41.5%. By replacing the acetone with a mixture of 45% acetone and 55% acetonitrile and then storing the liquid phase at −70°C overnight, the content and yield of EPA and DHA in the final liquid phase were 61.4 wt% and 66.2%, respectively.     

Lipase‐catalyzed synthesis of structured lipids with fatty acids fractionated from saponified chicken fat and menhaden oil

In this study, free fatty acids (FFA) of chicken fat and menhaden oil, which were obtained by saponification, were dry‐fractionated and solvent fractionated. Using these fractionation processes, FFA fractions enriched in monounsaturated (MUFA) and polyunsaturated fatty acids were obtained. Chicken fat FFA fractions enriched in MUFA were modified further by lipase‐catalyzed esterification with the starting fat to produce structured lipids of high MUFA content.     

Production of prostaglandins in homogenates of kidney medullae and cortices of spontaneously hypertensive rats fed menhaden oil

Menhaden oil (MO), whose polyunsaturated fatty acids consist mainly of (n−3) fatty acids, was fed to spontaneously hypertensive rats to determine the effect of (n−3) fatty acid on the in vitro production of prostaglandins produced from arachidonic acid (20∶4[n−6]). Capacity to form PGE₂ and PGF_2α was impaired in homogenates of kidney medullae and cortices from rats fed the MO diet compared to rats fed the control diet. The lower amounts of diene prostaglandins produced corresponded to the decrease in the amount of 20∶4 (n−6) in the tissue. Possibly changes produced in tissue lipids by dietary fatty acids affect prostaglandin production by reducing the availability of substrate in tissue lipids.     

Effect of varying proportions of dietary menhaden and corn oil on experimental rat mammary tumor promotion

Dose-related effects of long-chain highly unsaturated n−3 fatty acids on the development ofN-nitrosomethylurea (NMU)-induced rat mammary tumors were assessed in female F344 rats. Four test groups (36 rats/group) were fed the following high-fat (HF) diets (23% fat, w/w): Group 1, 18% menhaden oil (MO) and 5% corn oil (CO); Group 2, 11% MO and 11.8% CO; Group 3,5% MO and 18% CO; Group 4, CO alone. A fifth group, serving as an internal control, was fed a low-fat diet containing 5% CO alone. Experimental diets were begun after initiation with NMU, and the experiment was terminated 31 wk later. Total tumor numbers in the five groups were 28, 16, 32, 26 and 11, respectively, indicating that the promotion phase of NMU-induced carcinogenesis was significantly suppressed only when equal parts of CO and MO (Group 2) were fed or when CO alone was fed at 5% (w/w). At high (Group 1) or low (Group 3) levels of MO, tumor numbers were indistinguishable from the HF CO group (Group 4). The same pattern was observed when assessed in terms of cumulative tumor incidence and multiplicity. However, when expressed in terms of final tumor incidence, dietary MO did not suppress tumor promotion in a statistically significant fashion at any concentration. Animals fed MO gained weight at the same rate as those fed CO, indicating that the presence of MO in the diet did not result in food avoidance behavior. Measurement of total serum cholesterol indicated an inverse trend with respect to the MO content of the diet. Analysis of serum fatty acid profiles indicated that the proportion of n−3 and n−6 polyun-saturated fatty acids (PUFA) in the serum reflected that of the diet. These results support the hypothesis that the relative proportions of dietary n−3/n−6 fatty acids play an important role in the suppression of experimental mammary tumorigenesis and suggest that changes in circulating cholesterol or n−3 PUFA levels, induced by dietary MO, are not directly related to tumor development. Presented in part at the 81st Annual Meeting of the American Association for Cancer Research, Washington, D.C., May 1990     

Purification process for cod liver oil polyunsaturated fatty acids

The polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (EPA, 20∶5n−3) and docosahexaenoic acid (DHA, 22∶6n−3), which have several pharmaceutical properties, have been purified from cod liver oil. The process consisted of four main steps: (i) saponification of the oil, (ii) use of urea inclusion adducts method to obtain PUFA, (iii) PUFA methylation, and (iv) argentation silica gel column chromatography of the methylated PUFA. Argentation silica gel chromatography yielded highly pure DHA in the process (100% purity, 64% yiild). For EPA, the recovery in the combined process was 29.6%, and the final purity was 90.6%, owing to the simultaneous elution of other polyunsaturated fatty esters. The recovery in the urea inclusion method was strongly enhanced by application of orbital agitation during the crystallization process, in which EPA yield increased from 60–70% without agitation to 90–97% at 800 rpm; stearidonic acid (18∶4n−3) yield ranged from 60–75% without agitation to 87–95% at 800 rpm, and DHA yield varied from 53–73% without agitation to 85–99% at 800 rpm     

The enrichment of n−3 polyunsaturated fatty acids using aminopropyl solid phase extraction columns

A rapid, simple and reliable method is described for the preparation of concentrates of methyl or ethyl esters of n−3 polyunsaturated fatty acids by solid phase extraction using aminopropyl bonded silica columns. After applying mixtures of fatty acid esters in hexane, saturated and monounsaturated fatty acid esters are preferentially eluted with hexane whereas polyunsaturated fatty acids (PUFA) can subsequently be eluted with dichloromethane. Concentrates containing 80–90% n−3 PUFA can thus be obtained using fish oil fatty acids esters as a starting material.     

Enzyme-assisted acidolysis of menhaden and seal blubber oils with γ-linolenic acid

Oils containing both n−3 and n−6 fatty acids have important clinical and nutritional applications. Lipase-catalyzed acidolysis of seal blubber (SBO) and menhaden oils (MO) with γ-linolenic acid (GLA) was carried out in hexane. The process variables studied for lipase-catalyzed reaction were concentration of enzyme (100–700 units/g of oil), reaction temperature (30–60°C), reaction time (0–48 h), and mole ratio of GLA to triacylglycerols (TAG) (1∶1 to 5∶1). Two lipases chosen for acidolysis reaction were from Pseudomonas species (PS-30) and Mucor miehei. Lipase PS-30 was chosen over Mucor (also known as Rhizomucor) miehei to catalyze the acidolysis reaction owing to higher incorporation of GLA. For the acidolysis reaction, optimal conditions were a 3∶1 mole ratio of GLA to TAG, reaction temperature of 40°C, reaction time of 24 h, and an enzyme concentration of 500 units/g of oil. Under these conditions, incorporation of GLA was 37.1% for SBO and 39.6% for MO.     

Composition and seasonal variation of fatty acids of <Emphasis Type="Italic">Diplodus vulgaris</Emphasis> L. from the Adriatic Sea

Muscle tissue from the common two-banded sea bream Diplodus vulgaris L. originating from the Adriatic Sea, Croatia, was analyzed. The FA composition of neutral (TAG) and polar (PE, PC, PI/PS) lipid classes was determined, as well as the lipid and water contents during winter and summer periods. Both the total lipid and water contents were higher in the winter period. We identified 16 different FA. The major constituents of the total FA in both seasons were saturates: palmitic (16∶0) and stearic acids (18∶0); monoenes: oleic (18∶1n−9) and palmitoleic acids (16∶1n−7); and polyunsaturates: arachidonic acid (20∶4n−6), EPA (20∶5n−3), and DHA (22∶6n−3), but their amounts and ratios differed significantly between the two seasons and between lipid fractions. The FA composition showed a noticeable pattern of seasonality that reflected fluctuations mainly in TAG. The diminution of the monounsaturated FA content in the summer was clearly followed by an increase in PUFA content. Diplodus vulgaris is a good source of natural n−3 PUFA and would therefore be suitable for inclusion in highly unsaturated low-fat diets.     

Polyunsaturated fatty acid concentrates from borage and linseed oil fatty acids

A modified low-temperature solvent crystallization process was employed for the enrichment of polyunsaturated fatty acids (PUFA) in borage and linseed oil fatty acids. The effects of solvent, operation temperature, and solvent to free fatty acid (FFA) ratio on the concentration of PUFA were investigated. The best results were achieved when a mixture of 30% acetonitrile and 70% acetone was used as the solvent. With an operation temperature of −80°C and a solvent to FFA ratio of 30 mL/g, γ-linolenic acid (GLA) in FFA of saponified borage oil can be raised from 23.4 to 88.9% with a yield of 62.0%. At a yield of 24.9%, α-linolenic acid in linseed oil can be increased from 55.0 to 85.7%. The results of this work are comparable to the best results available in the literature.     

Lipid content and fatty acid composition of 11 species of Queensiand (Australia) fish

The fatty acid composition of 11 species of fish caught off the northeast coast of Australia was determined. No fatty acid profiles have been previously published for fish from this area nor for nine of these species. Although the percentage of polyunsaturated fatty acid (PUFA) was the same as the calculated average for Australian fish (42.3%), the percentage of n−3 fatty acids was lower (24.4±5.4% vs. 30.7±10.1%) and the n−6 fatty acids higher (16.5±4.5% vs. 11.2±5.9%), P<0.001 in each case. The major n−3 PUFA were docosahexaenoic (15.6 ±6.3%) and eicosapentaenoic acid (4.3±1.1%) while the major n−6 PUFA were arachidonic (8.3±3.2%) and n−6 docosatetraenoic acid (3.1±1.3%). The second-most abundant class of fatty acid was the saturates (31.6±3.5%) while the monounsaturates accounted for 17.4±4.3% of the total fatty acids. The monounsaturate with the highest concentration was octadecenoic acid (11.8±2.6%). There was a positive correlation between the total lipid content and saturated and monounsaturated fatty acids (r=0.675 and 0.567, respectively) and a negative correlation between the total lipid content and PUFA (r=0.774).     

Influence of diet on fatty acids of three subtropical fish, subfamily caesioninae (Caesio diagramma and C. tile) and family siganidae (Siganus canaliculatus)

The total lipid and fatty acid compositions of tissues and the stomach contents of three subtropical marine fish species, subfamily Caesioninae, Caesio diagramma and C. tile, and family Siganidae Siganus canaliculatus, were investigated to clarify the differences between these species. Triacylglycerols (TAG) were the dominant depot lipids of the three species, whereas wax esters were found as a minor component. In particular, muscle lipids were found to contain mainly glycerol derivatives such as TAG and phospholipids. The major fatty acids identified in the three species were 16∶0, 18∶0, 18∶1n−9, and 22∶6n−3 (docosahexaenoic acid, DHA). In addition, noticeable levels of 16∶1n−7, 18∶1n−7, 20∶4n−6 (arachidonic acid, AA), and 20∶5n−3 (eicosapentaenoic acid) were found. DHA was the most abundant polyunsaturated fatty acid (PUFA) in the muscle and viscera lipids of the three species. The high DHA levels in the lipids of all the organs were found to be higher than those of the lipid extracted from the stomach contents of the three fishes. In addition, the specimens of S. canaliculatus contained significantly higher levels of AA in its tissues than did the other two species. A high AA content is unusual since such high levels of n−6 PUFA are rarely found in higher marine organisms. These levels may be due to its characteristic feeding pattern, because S. canaliculatus prefer and mainly feed on seaweed, which often contains high amounts of n−6 PUFA, such as linoleic acid (18∶2n−6) and AA.     

Enzymatic acidolysis in hexane to produce n−3 or n−6 FA-enriched structured lipids from coconut oil: Optimization of reactions by response surface methodology

Response surface methodology is a statistical design that helps one to determine optimal conditions for an enzyme-catalyzed reaction by performing a minimal number of experiments. This methodology was adapted for modifying coconut oil TAG by using lipase-catalyzed acidolysis in hexane to incorporate n−3 or n−6 PUFA. FFA obtained after hydrolysis of cod liver oil and safflower oil were used as acyl donors. Immobilized lipase, Lipozyme IM60, from Rhizomucor miehei was used for catalyzing the reaction. The reaction conditions—substrate molar ratio, incubation time, and temperature—were optimized. The experimental data were fitted to a response function based on the central composite rotatable design. The optimal conditions generated from models indicated that maximal incorporation of n−3 PUFA occurred at a 1∶4 molar ratio of TAG/FFA when incubation was carried out for 34 h at 54°C. Similarly, maximal incorporation of n−6 FA was predicted at a 1∶3 molar ratio of TAG/FFA when incubated for 48.5 h at 39°C. Experiments conducted at optimized conditions predicted by the equation obtained from response surface methodology yielded structured lipids with 13.65 and 45.5% of n−3 and n−6 FA, respectively. These values agreed well with that predicted by the model. The reactions were also scaled up to 100 g levels in batch reactors with the incorporation level of n−3 and n−6 fatty acids agreeing closely with that observed when the reactions were carried out at lab scale (100 mg). These studies indicated that response surface methodology is a useful tool in predicting the conditions for incorporating desired levels of specific FA during the synthesis of structured lipids.     

Fatty acid composition of macrophage phospholipids in mice fed fish or borage oil

The polyunsaturated fatty acid (PUFA) composition of murine peritoneal macrophage phospholipids was dramatically altered in vivo following the four-wk feeding of specific dietary oils. Fish oil (containing 20∶5n–3 and 22∶6n−3) feeding significantly increased macrophage 20∶5n−3, 22∶5n−3, and 22∶6n−3 (P<0.05), while borage oil (containing 18∶2n−6 and 18∶3n−6) increased (P<0.05) the macrophage 20∶3n−6/20∶4n−6 ratio, relative to safflower oil (containing 18∶2n−6) and hydrogenated coconut oil (containing 12∶0)-fed animals. The macrophage phospholipid PUFA profiles were compared with those of the liver, lung and spleen. The significance of the PUFA alterations is discussed.     

Alteration in mouse splenic phospholipid fatty acid composition and lymphoid cell populations by dietary fat

The fatty acid composition of diacyl- and alkylacylglycerophosphocholine (PC), phosphatidylinositol (PI), phosphatidylserine (PS), alkenylacyl-glycerophosphoethanolamine (aPE), and diacyl- and alkylacyl-glycerophosphoethanolamine (dPE) was assessed in isolated splenocytes from C3H/Hen mice fed one of four purified isocaloric diets for six weeks. Diets contained 20% by weight of either a high-linoleate sunflower oil (Hi 18∶2), a high-oleate sunflower oil (Hi 18∶1), a mixture of 17% menhaden fish oil and 3% high-linoleate sunflower oil (Hi n−3), or a mixture of 17% coconut oil and 3% high-linoleate sunflower oil (Hi SFA). Spleen weight and immune cell yield were significantly higher (P<0.05) in mice fed the Hi 18∶1 or the Hi n−3 diets compared with those fed the Hi 18∶2 and Hi SFA diets. Distinctive patterns of fatty acids were observed for each phospholipid in response to dietary fatty acids. Dietary fat significantly affected (P<0.05) total polyunsaturated fatty acids (PUFA) in PC and dPE, total saturated fatty acids (SFA) in PC, total monounsaturated fatty acids (MUFA), and n−3 PUFA in all phospholipid classes examined. In mice fed the Hi n−3 diet, n−3 PUFA were significantly elevated, whereas n−6 PUFA decreased in all of the phospholipids. In these mice, eicosapentaenoic acid (EPA) was the predominant n−3 PUFA in PC and PI, whereas docosahexaenoic acid (DHA) was the major n−3 PUFA in aPE and PS. Interestingly, the ratios of n−3/n−6 PUFA in the phospholipids from these mice were 3.2, 2.4, 1.8, 0.8 and 0.8 for aPE, PS, dPE, PC and PI, respectively. These data suggest a preferential incorporation of n−3 PUFA into aPE, PS and dPE over PC and PI.     

Enzymatic modification of evening primrose oil: Incorporation of n−3 polyunsaturated fatty acids

Immobilized lipase SP435 fromCandida antaractica was used as a biocatalyst for the modification of the fatty acid composition of evening primrose oil by incorporating n−3 polyunsaturated fatty acid (PUFA) and eicosapentaenoic acid (EPA). Transesterification (ester-ester interchange) was conducted in organic solvent or without solvent, with EPA ethyl ester (EEPA) as the acyl donor. Products were analyzed by gas-liquid chromatography (GLC). After 24-h incubation in hexane, the fatty acid composition of evening primrose oil was markedly changed to contain up to 43% EPA. The amount of 18:2n−6 PUFA was reduced by 32%, and the saturated fatty acid content was also reduced. The effects of incubation time, molar ratio, enzyme load, and reaction medium on mol% EPA incorporation were also studied. Generally, as the incubation time (up to 24 h), molar ratio, and enzyme load increased, EPA incorporation also increased. Evening primrose oil, containing EPA and γ-linolenic acid (18:3n−6) in the same glycerol backbone, was successfully produced and may be more beneficial for certain applications than unmodified oil.     

Lipid composition and prostaglandin synthesis in mouse lung microsomes: Alterations following the ingestion of menhaden oil

Three groups of male mice were fed a normal diet or a semisynthetic diet containing either 10% hydrogenated coconut oil (CO group) or 10% menhaden oil (MO group) for two wk. The synthetic diet altered the fatty acid composition of lung microsomal lipids. Mice ingesting menhaden oil contained greater amounts of eicosapentaenoic acid (20∶5 n−3), docosapentaenoic acid (22∶5 n−3) and docosahexaenoic acids (22∶6 n−3) and decreased amounts of n−6 fatty acids such as arachidonic and adrenic. Synthesis of prostaglandin E₂ and prostaglandin F_2α from exogenous arachidonic acid was significantly depressed in n−3 fatty acid-enriched lung microsomes. These studies indicated that dietary fish oil not only alters the fatty acid composition of lung microsomes but also lowers the capacity of lungs to synthesize prostaglandins from arachidonic acid.     

Fatty acyl desaturation in isolated hepatocytes from Atlantic salmon (Salmo salar): Stimulation by dietary borage oil containing γ-linolenic acid

The effects of different dietary oils on the fatty acid compositions of liver phospholipids and the desaturation and elongation of [1-¹⁴C]18∶3n−3 and [1-¹⁴C]18∶2n−6 were investigated in isolated hepatocytes from Atlantic salmon. Atlantic salmon smolts were fed diets containing either a standard fish oil (FO) as a control diet, a 1∶1 blend of Southern Hemisphere marine oil and tuna orbital oil (MO/TO), sunflower oil (SO), borage oil (BO), or oliver oil (OO) for 12 wk. The SO and BO diets significantly increased the percentages of 18:2n−6, 18:3n−6, 20:2n−6, 20:3n−6, and total n-6 polyunsaturated fatty acids (PUFA) in salmon liver lipids in comparison with the FO diet. The BO diet also increased the percentage of 20:4n−6. Both the SO and BO diets significantly reduced the percentages of all n−3 PUFA in comparison with the FO diet. The OO diet significantly increased the percentages of 18:1n−9, 18:2n−6, total monoenes, and total n−6 PUFA in liver lipids compared to the FO diet, and the percentages of all n−3 PUFA were significantly reduced. With [1-¹⁴C]18:3n−3, the recovery of radioactivity in the products of Δ6 desaturation was significantly greater in the hepatocytes from salmon fed SO, BO, and OO in comparison with the FO diet. The BO diet also increased the recovery of radioactivity in the products of Δ5 desaturation. Only the BO diet significantly affected the desaturation of [1-¹⁴C]18:2n−6, increasing recovery of radioactivity in both Δ6- and Δ5-desaturation products. In conclusion, dietary BO, enriched in γ-linolenic acid (18:3n−6), significantly increased the proportions of both 20:3n−6 and 20:4n−6 in salmon liver phospholipids and also significantly increased the desaturation of both 18:2n−6 and 18:3n−3 in salmon hepatocytes. The possible relationships between dietary fatty acid composition, tissue phospholipid fatty acid composition, and desaturation/elongation activities are discussed.     

Effect of n−3 fatty acid-rich fish oil supplementation on the oxidation of low density lipoproteins

This study was aimed at determining the effect of fish oil supplementation on copper-catalyzed oxidation of low density lipoproteins (LDL) from nine hypertriglyceridemic human subjects. A rapid headspace gas chromatographic method was used to measure the volatile oxidation products from LDL. Propanal and hexanal were the major volatile products formed in the oxidation of n−3 and n−6 polyunsaturated fatty acids (PUFA), respectively. Fish oil supplementation resulted in a significant increase in propanal formation from 3.7 to 13.4 nmol/mL LDL (P<0.01); it also resulted in small decreases in pentanal formation from 14.7 to 11.4 nmol/mL LDL and in hexanal formation from 138 to 108 nmol/mL LDL (P<0.05). The changes in peroxidation products paralleled the changes in LDL composition, which showed a significant increase in n−3 PUFA from 3.2 to 14.6% (P<0.01) and a decrease in n−6 PUFA from 43.7 to 35.0% (P<0.05). Propanal formation was highly and significantly correlated with n−3 PUFA content (r=0.950,P<0.001). Since total volatiles remained unchanged, this indicated that the two groups of LDL samples did not differ in overall oxidative susceptibility. Although fish oil intake did not alter the oxidative susceptibility of LDL, the chemically modified LDL particles generated a distinct pattern of volatile oxidation products that reflected changes in their fatty acid composition.     

Effects of dietary linseed oil and marine oil on lipid peroxidation in monkey liverin vivo andin vitro

Diets rich in linoleic acid (CO) from corn oil, or in linoleic acid and either α-linolenic acid (LO) based on linseed oil or n−3 fatty acids (MO) from menhaden oil were fed to male and female Cynomolgus monkeys for 15 wk. In the liver a 40% reduction of α-tocopherol occurred in the MO group relative to the CO and LO groups followed by increased formation of lipofuscinin vivo. A four-fold increase of α-tocopherol in the MO diet (MO+E) brought the level in the liver to that found with CO and LO. The increased peroxidation in the MO group in the liver phospholipids was associated with the replacement of 60% of the n−6 fatty acids by n−3 fatty acids from menhaden oil. Similar fatty acid profiles were found in groups fed MO and MO+E, respectively. Compared to the CO fed group, feeding α-linolenic acid only resulted in a slight incorporation of n−3 fatty acids in the liver membranes mainly due to a direct incorporation of α-linolenic acid. However, in monkeys fed menhaden oil more than 30% of the total fatty acids in the liver phospholipids were n−3 fatty acids. The various diets did not influence the activity of liver catalase (EC 1.11.1.6) nor superoxide dismutase (EC 1.15.1.1), but glutathione-peroxidase activity (EC 1.11.1.9) was higher in monkeys fed the MO diet. The catalase activity in females was 20% higher than in males. In anin vitro assay, liver microsomes from monkeys fed the MO diet or the MO diet supplemented with tocopherol produced similar amounts of thiobarbituric acid reactive substances and at a much higher rate than microsomes from the CO and LO groups. It appeared that α-tocopherol did not protect long-chain n−3 C₂₀ and C₂₂ fatty acids as well as n−6 fattya acids against peroxidation. The present data showed that monkeys were not fully able to compensate for increased peroxidative stress but a four-fold supplement of vitamin E to the diets reduced the oxidation.