Showing papers on "Fish oil published in 2000"

Differential Effects of Eicosapentaenoic Acid and Docosahexaenoic Acid on Vascular Reactivity of the Forearm Microcirculation in Hyperlipidemic, Overweight Men

Abstract: Background—Recent evidence supports differential effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the 2 major ω3 fatty acids of marine origin, on blood pressure in humans and vascular reactivity in adult spontaneously hypertensive rats. We investigated possible differences in the effects of purified EPA or DHA on forearm vascular reactivity in overweight hyperlipidemic men that might contribute to the blood pressure–lowering effects of fish oils. Methods and Results—With a double-blind, placebo-controlled trial of parallel design, 59 overweight, mildly hyperlipidemic men were randomized to receive 4 g/d purified EPA, DHA, or olive oil (placebo) capsules while continuing their usual diets for 6 weeks. Forearm blood flow (FBF) was measured with venous occlusion, strain-gauge plethysmography during the sequential intra-arterial administration of acetylcholine (7.5, 15, and 30 μg/min), sodium nitroprusside (1.5, 3, and 10 μg/min), norepinephrine (10, 20, and 40 ng/min), a single-dose inf...

Fish oil-derived fatty acids, docosahexaenoic acid and docosapentaenoic acid, and the risk of acute coronary events: the Kuopio ischaemic heart disease risk factor study.

Abstract: Background—Previous findings concerning the serum levels of fish-derived (n-3) fatty acids and coronary heart disease are inconsistent The purpose of this study was to investigate the association between the serum n-3 end-product fatty acids docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), and eicosapentaenoic acid and the risk of acute coronary events in middle-aged men Methods and Results—We studied this association in the Kuopio Ischaemic Heart Disease Risk Factor Study, a prospective population study in Eastern Finland Subjects were randomly selected and included 1871 men aged 42 to 60 years who had no clinical coronary heart disease at baseline examination A total of 194 men had a fatal or nonfatal acute coronary event during follow-up In a Cox proportional hazards’ model adjusting for other risk factors, men in the highest fifth of the proportion of serum DHA+DPA in all fatty acids had a 44% reduced risk (P=0014) of acute coronary events compared with men in the lowest fifth Men in th

Encapsulated fish oil enriched in α-tocopherol alters plasma phospholipid and mononuclear cell fatty acid compositions but not mononuclear cell functions.

Abstract: Background Several studies have reported that dietary fish oil (FO) supplementation alters cytokine production and other functional activities of peripheral blood mononuclear cells (PBMC). However, few of these studies have been placebo controlled and few have related the functional changes to alterations in PBMC fatty acid compositionPatients and methods Healthy subjects supplemented their diets with 9 g day(-1) of encapsulated placebo oil (3:1 mix of coconut and soybean oils), olive oil (OO), safflower oil (SO), evening primrose oil (EPO) or FO [providing 2.1 g eicosapentaenoic acid (EPA) plus 1.1 g docosahexaenoic acid (DHA) per day] for 12 weeks; the capsules also provided 205 mg alpha-tocopherol per day. Blood was sampled at 4-weekly intervals and plasma and PBMC prepared. Plasma phospholipid and PBMC fatty acid composition, plasma alpha-tocopherol and thiobarbituric acid-reactive substance concentrations, plasma total antioxidant capacity, the proportions of different PBMC subsets, the proportions of PBMC expressing the adhesion molecules CD2, CD11b and CD54, and PBMC functions (lymphocyte proliferation, natural killer cell activity, cytokine production) were measured. All measurements were repeated after a 'washout' period of 8 weeks.Results The placebo, OO and SO capsules had no effect on plasma phospholipid or PBMC fatty acid composition. The proportion of dihomo-gamma-linolenic acid in plasma phospholipids was elevated in subjects taking EPO and was decreased in subjects taking FO. There was no appearance of gamma-linolenic acid in the plasma phospholipids or PBMC in subjects taking EPO. There was a marked increase in the proportion of EPA in the plasma phospholipids (10-fold) and PBMC (four-fold) of subjects taking FO supplements; this increase was maximal after 4 weeks of supplementation. There was an increase in the proportion of DHA in plasma phospholipids and PBMC, and an approximately 20% decrease in the proportion of arachidonic acid in plasma phospholipids and PBMC, during FO supplementation. Plasma concentrations of alpha-tocopherol were significantly elevated during supplementation in all subjects and returned to baseline values after the washout period. There were no effects of supplementation with any of the capsules on total plasma antioxidant activity or plasma thiobarbituric acid-reactive substances or on the proportion of different PBMC subsets, on the proportion of PBMC expressing adhesion molecules, on natural killer cell activity, on the proliferation of mitogen-stimulated. whole blood cultures or PBMC, or on the ex: vivo production of a range of cytokines by whole blood cultures or PBMC cultures stimulated by either concanavalin A or lipopolysaccharide.Conclusion Supplementation of the diet with 3.2 g EPA plus DHA per day markedly alters plasma phospholipid and PBMC fatty acid compositions. The lack of effect of FO upon PBMC functions may relate to the level of or-tocopherol included in the supplements.

ApoE Polymorphism and Fish Oil Supplementation in Subjects With an Atherogenic Lipoprotein Phenotype

Abstract: The study assessed the efficacy of fish oil supplementation in counteracting the classic dyslipidemia of the atherogenic lipoprotein phenotype (ALP). In addition, the impact of the common apolipoprotein E (apoE) polymorphism on the fasting and postprandial lipid profile and on responsiveness to the dietary intervention was established. Fifty-five ALP males (aged 34 to 69 years, body mass index 22 to 35 kg/m(2), triglyceride [TG] levels 1.5 to 4.0 mmol/L, high density lipoprotein cholesterol [HDL-C] 40% total LDL) completed a randomized placebo-controlled crossover trial of fish oil (3.0 g eicosapentaenoic acid/docosahexaenoic acid per day) and placebo (olive oil) capsules with the 6-week treatment arms separated by a 12-week washout period. In addition to fasting blood samples, at the end of each intervention arm, a postprandial assessment of lipid metabolism was carried out. Fish oil supplementation resulted in a reduction in fasting TG level of 35% (P<0.001), in postprandial TG response of 26% (TG area under the curve, P<0.001), and in percent LDL-3 of 26% (P<0.05). However, no change in HDL-C levels was evident (P=0.752). ANCOVA showed that baseline HDL-C levels were significantly lower in apoE4 carriers (P=0.035). The apoE genotype also had a striking impact on lipid responses to fish oil intervention. Individuals with an apoE2 allele displayed a marked reduction in postprandial incremental TG response (TG incremental area under the curve, P=0.023) and a trend toward an increase in lipoprotein lipase activity relative to non-E2 carriers. In apoE4 individuals, a significant increase in total cholesterol and a trend toward a reduction in HDL-C relative to the common homozygous E3/E3 profile was evident. Our data demonstrate the efficacy of fish oil fatty acids in counteracting the proatherogenic lipid profile of the ALP but also that the apoE genotype influences responsiveness to this dietary treatment.

Fish oil supplementation in type 2 diabetes: a quantitative systematic review.

Abstract: OBJECTIVE: To determine the effects of fish oil supplementation on lipid levels and glycemic control in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: A comprehensive search of Medline, Embase, Lilacs, the Cochrane Clinical Trials Registry bibliographies of relevant papers, and expert input updated through September 1998 was undertaken. All randomized placebo-controlled trials were included in which fish oil supplementation was the only intervention in subjects with type 2 diabetes. Three investigators performed data extraction and quality scoring independently with discrepancies resolved by consensus. Eighteen trials including 823 subjects followed for a mean of 12 weeks were included. Doses of fish oil used ranged from 3 to 18 g/day The outcomes studied were glycemic control and lipid levels. RESULTS: Meta-analysis of pooled data demonstrated a statistically significant effect of fish oil on lowering triglycerides (-0.56 mmol/l [95% CI -0.71 to -0.41]) and raising LDL cholesterol (0.21 mmol/l [0.02 to 0.41]). No statistically significant effect was observed for fasting glucose. HbA1c total cholesterol, or HDL cholesterol. The triglyceride-lowering effect and the elevation in LDL cholesterol were most marked in those trials that recruited hypertriglyceridemic subjects and used higher doses of fish oil. Heterogeneity was observed and explained by the recruitment of subjects with baseline hypertriglyceridemia in some studies. CONCLUSIONS: Fish oil supplementation in type 2 diabetes lowers triglycerides, raises LDL cholesterol, and has no statistically significant effect on glycemic control. Trials with hard clinical end points are needed.

Dietary supplementation with fish oil rich in omega-3 polyunsaturated fatty acids in children with bronchial asthma.

Abstract: Omega-3 polyunsaturated fatty acids have anti-inflammatory effects in vitro, and high dietary levels are associated with a lower incidence of inflammatory diseases. However, only limited effects have been demonstrated in asthma. The effects of dietary supplementation with fish oil for 10 months in 29 children with bronchial asthma was investigated in a randomized controlled fashion. In order to minimize the effects of environmental inhaled allergens and diet, this study was performed in a long-term treatment hospital. Subjects received fish oil capsules containing 84 mg eicosapentaenoic acid (EPA) and 36 mg docosahexaenoic acid (DHA) or control capsules containing 300 mg olive oil. The daily dosages of EPA and DHA were 17.0-26.8 and 7.3-11.5 mg x kg body weight(-1), respectively. Asthma symptom scores decreased and responsiveness to acetylcholine decreased in the fish oil group but not in the control group. In addition, plasma EPA levels increased significantly only in the fish oil group (p<0.0088). No significant side-effects were observed. The present results suggest that dietary supplementation with fish oil rich in the omega-3 polyunsaturated fatty acids eicosapentaenoic acid and docosahexaenoic acid is beneficial for children with bronchial asthma in a strictly controlled environment in terms of inhalant allergens and diet.

Dietary marine fatty acids (fish oil) for asthma in adults and children

Abstract: BACKGROUND Epidemiological studies suggest that a diet high in marine fatty acids (fish oil) may have beneficial effects on inflammatory conditions such as rheumatoid arthritis and possibly asthma. OBJECTIVES 1. To determine the effect of marine n-3 fatty acid (fish oil) supplementation in asthma. 2. To determine the effect of a diet high in fish oil in asthma. SEARCH STRATEGY The Cochrane Airways Review Group register was searched using the terms: marine fatty acids OR diet OR nutrition OR fish oil OR eicosapentaenoic acid OR EPA. Bibliographies of retrieved trials were searched and fish oil manufacturers contacted. SELECTION CRITERIA Randomised controlled trials in patients with asthma more than two years of age were included. The study duration had to be in excess of four weeks. Double blind trials were preferred, but single-blind and open trials were also reviewed for possible inclusion. Three reviewers read each paper, blind to its identity. Decisions concerning inclusion were made by simple majority. Quality assessment was performed by all three reviewers independently. DATA COLLECTION AND ANALYSIS The only comparison possible was between marine n-3 fatty acid supplementation and placebo. There were insufficient trials to examine dietary manipulation alone. MAIN RESULTS Nine randomised controlled trials conducted between 1986 and 2001 satisfied the inclusion criteria. Seven were of parallel design and two were cross-over studies. Eight compared fish oil with placebo whilst one compared high dose vs low dose marine n-3 fatty acid supplementation. Two studies were conducted in children, whilst the remaining seven studies were conducted in adults. None of the included studies reported asthma exacerbations, health status or hospital admissions. There was no consistent effect on any of the analysable outcomes: FEV1, peak flow rate, asthma symptoms, asthma medication use or bronchial hyper reactivity. One of the studies performed in children which combined dietary manipulation with fish oil supplementation showed improved peak flow and reduced asthma medication use. There were no adverse events associated with fish oil supplements. REVIEWER'S CONCLUSIONS There is little evidence to recommend that people with asthma supplement or modify their dietary intake of marine n-3 fatty acids (fish oil) in order to improve their asthma control. Equally, there is no evidence that they are at risk if they do so.

Effect of low-to-moderate amounts of dietary fish oil on neutrophil lipid composition and function.

Abstract: Although essential to host defense, neutrophils are also involved in numerous inflammatory disorders including rheumatoid arthritis. Dietary supplementation with relatively large amounts of fish oil [containing >2.6 g eicosapentaenoic acid (EPA) plus 1.4 g docosahexaenoic acid (DHA) per day] can attenuate neutrophil functions such as chemotaxis and superoxide radical production. In this study, the effects of more moderate supplementation with fish oil on neutrophil lipid composition and function were investigated. The rationale for using lower supplementary doses of fish oil was to avoid adverse gastrointestinal problems, which have been observed at high supplementary concentrations of fish oil. Healthy male volunteers aged <40 yr were randomly assigned to consume one of six dietary supplements daily for 12 wk (n = 8 per treatment group). The dietary supplements included four different concentrations of fish oil (the most concentrated fish oil provided 0.58 g EPA plus 1.67 g DHA per day), linseed oil, and a placebo oil. The percentages of EPA and DHA increased (both P < 0.05) in neutrophil phospholipids in a dose-dependent manner after 4 wk of supplementation with the three most concentrated fish oil supplements. No further increases in EPA or DHA levels were observed after 4 wk. The percentage of arachidonic acid in neutrophil phospholipids decreased (P < 0.05) after 12 wk supplementation with the linseed oil supplement or the two most concentrated fish oil supplements. There were no significant changes in N-formyl-met-leu-phe-induced chemotaxis and superoxide radical production following the dietary supplementations. In conclusion, low-to-moderate amounts of dietary fish oil can be used to manipulate neutrophil fatty acid composition. However, this may not be accompanied by modulation of neutrophil functions such as chemotaxis and superoxide radical production.

Polyunsaturated fatty acid metabolism in Atlantic salmon (Salmo salar) undergoing parr-smolt transformation and the effects of dietary linseed and rapeseed oils.

Abstract: Duplicate groups of Atlantic salmon parr were fed diets containing either fish oil (FO), rapeseed oil (RO), linseed oil (LO) or linseed oil supplemented with arachidonic acid (20:4n-6; AA) (LOA) from October (week 0) to seawater transfer in March (week 19). From March to July (weeks 20–34) all fish were fed a fish oil-containing diet. Fatty acyl desaturation and elongation activity in isolated hepatocytes incubated with [1-14C]18:3n-3 increased in all dietary groups, peaking in early March about one month prior to seawater transfer. Desaturation activities at their peak were significantly greater in fish fed the vegetable oils, particularly RO, compared to fish fed FO. Docosahexaenoic acid (22:6n-3:DHA) and AA in liver and gill polar lipids (PL) increased in all dietary groups during the freshwater phase whereas eicosapentaenoic acid (20:5n-3; EPA) increased greatly in all groups after seawater transfer. The AA/EPA ratio in tissue PL increased up to seawater transfer and then decreased after transfer. AA levels and the AA/EPA ratio in gill PL were generally higher in the LOA group. The levels of 18:3n-3 in muscle total lipid were increased significantly in the LO, LOA and, to a lesser extent, RO groups prior to transfer but were reduced to initial levels by the termination of the experiment (week 34). In contrast, 18:2n-6 in muscle total lipid was significantly increased after 18 weeks in fish fed the diets supplemented with RO and LO, and was significantly greater in the FO and RO groups at the termination of the experiment. Gill PGF production showed a large peak about two months after transfer to seawater. The production of total PGF post-transfer was significantly lower in fish previously fed the LOA diet. However, plasma chloride concentrations in fish subjected to a seawater challenge at 18 weeks were all lower in fish fed the diets with vegetable oils. This effect was significant in the case of fish receiving the diet with LOA, compared to those fed the diet containing FO. The present study showed that during parr-smolt transformation in Atlantic salmon there is a pre-adaptive increase in hepatocyte fatty acyl desaturation/elongation activities that is controlled primarily by environmental factors such as photoperiod and temperature but that can also be significantly modulated by diet. Feeding salmon parr diets supplemented with rapeseed or linseed oils prevented inhibition of the desaturase activities that is induced by feeding parr diets with fish oils and thus influenced the smoltification process by altering tissue PL fatty acid compositions and eicosanoid production. These effects, in turn, had a beneficial effect on the ability of the fish to osmoregulate and thus adapt to salinity changes.

Efficacy of fish oil concentrate in the treatment of rheumatoid arthritis.

Abstract: Objective. To determine the efficacy of fish oil derived (n-3) fatty acid supplementation (3-6 capsules/day) in subjects with rheumatoid arthritis (RA) whose (n-6) fatty acid intake in the background diet was < 10 g/day, compared to olive/corn oil capsule supplement over a 15 week period. Methods. A placebo controlled, double blind, randomized 15 week study to determine the effect of supplementation on clinical variables in 50 subjects with RA whose background diet was naturally low in (n-6) fatty acids. Fish oil containing 60% (n-3) fatty acids was supplemented at a rate of 40 mg/kg body weight. Results. Analysis of 9 clinical variables indicated there was a significant difference (p < 0.02) between control and treatment groups. Five subjects in the treatment group and 3 in the control group met the American College of Rheumatology 20% improvement criteria. Dietary supplementation resulted in a significant increase in eicosapentaenoic acid in plasma and monocyte lipids in the supplemented group. Conclusion. The findings suggest that fish oil supplementation that delivers (n-3) fatty acids at a dose of 40 mg/kg body weight/day, with dietary (n-6) fatty acid intake < 10 g/day in the background diet, results in substantial cellular incorporation of (n-3) fatty acids and improvements in clinical status in patients with RA.

Effect of olive oil on early and late events of colon carcinogenesis in rats: modulation of arachidonic acid metabolism and local prostaglandin E2 synthesis

Abstract: BACKGROUND—Animal model studies have shown that the colon tumour promoting effect of dietary fat depends not only on the amount but on its fatty acid composition. With respect to this, the effect of n9 fatty acids, present in olive oil, on colon carcinogenesis has been scarcely investigated. AIMS—To assess the effect of an n9 fat diet on precancer events, carcinoma development, and changes in mucosal fatty acid composition and prostaglandin (PG)E2 formation in male Sprague-Dawley rats with azoxymethane induced colon cancer. METHODS—Rats were divided into three groups to receive isocaloric diets (5% of the energy as fat) rich in n9, n3, or n6 fat, and were administered azoxymethane subcutaneously once a week for 11 weeks at a dose rate of 7.4 mg/kg body weight. Vehicle treated groups received an equal volume of normal saline. Groups of animals were colectomised at weeks 12 and 19 after the first dose of azoxymethane or saline. Mucosal fatty acids were assessed at 12 and 19 weeks. Aberrant crypt foci and the in vivo intracolonic release of PGE2 were assessed at week 12, and tumour formation at week 19. RESULTS—Rats on the n6 diet were found to have colonic aberrant crypt foci and adenocarcinomas more often than those consuming either the n9 or n3 diet. There were no differences between the rats on the n9 and n3 diets. On the other hand, administration of both n9 and n3 diets was associated with a decrease in mucosal arachidonate concentrations as compared with the n6 diet. Carcinogen treatment induced an appreciable increase in PGE2 formation in rats fed the n6 diet, but not in those fed the n3 and n9 diets. CONCLUSIONS—Dietary olive oil prevented the development of aberrant crypt foci and colon carcinomas in rats, suggesting that olive oil may have chemopreventive activity against colon carcinogenesis. These effects may be partly due to modulation of arachidonic acid metabolism and local PGE2 synthesis. Keywords: olive oil; fish oil; azoxymethane; carcinogenesis; fatty acids; prostaglandin E2

Rumen biohydrogenation of n-3 polyunsaturated fatty acids and their effects on microbial efficiency and nutrient digestibility in sheep

Abstract: The study examined the extent to which n-3 PUFA from different sources were biohydrogenated in the rumen and their effects on rumen microbial efficiency and whole tract nutrient digestibility. Four ruminally and duodenally cannulated wether lambs were used in a 4×4 Latin square design. Four iso-energetic and iso-nitrogenous diets based on dried grass were formulated to provide similar fat levels (60g/kg DM) from different sources; Megalac (palmitic acid: C16:0; Control), whole linseed (α-linolenic acid, C18:3n-3 ; Linseed) fish oil (eicosapentaenoic acid, C20:5n-3, EPA and docosahexaenoic acids C22:6n-3, DHA; Fish oil) and whole linseed plus fish oil providing equal amounts of oil (LinFish). Diets were offered at a rate of 1·2kg/day in 12 equal portions.Total fatty acid intake was similar on all diets whilst duodenal fatty acid flow varied between 101, 94, 87 and 90% of dietary intake for animals fed the Control, Linseed, Fish oil and Linfish diets respectively. Duodenal flow of C18:3 n-3 in animals fed the Linseed diet was twice that of animals fed the Control diet (P < 0·01) whilst animals fed the Fish oil diet had a significantly greater flow of EPA and DHA than those fed any of the other dietary treatments. Duodenal flow of trans C18:1 in animals fed the Linfish diet was significantly greater than that in animals fed either Linseed, Fish oil or Control diets (P < 0·001). Biohydrogenation of C18:3n-3 was 80 to 93% in all diets whilst that of C20:5n-3 and C22:6n-3 was 72 to 79% in diets that contained fish oil or linseed and fish oil. Apparent fatty acid digestibility (duodenum to rectum) tended to be greater for unsaturated than saturated fatty acids whilst whole tract fatty acid digestibility (mouth to rectum) was significantly greater in animals fed diets containing fish oil (P0·05). All dietary n-3 PUFA sources decreased microbial protein synthesis and efficiency when expressed as either gN/kg organic matter (OM) apparently or truly degraded in the rumen. Additionally, the inclusion of fish oil increased the proportion of propionate in the rumen whilst depressing the rumen digestibility of OM and fibre (P < 0·01), but had no significant effect on whole tract OM or fibre digestibility.

Effect of breed on the deposition in beef muscle and adipose tissue of dietary n-3 polyunsaturated fatty acids.

Abstract: This study investigated the effects of dietary n-3 polyunsaturated fatty acids (PUFA) on muscle fatty acid composition and content in two cattle breeds; the Holstein-Friesian, a dairy breed, and the Welsh Black, a traditional beef breed. Animals were kept on ad libitum grass silage and one of three concentrates varying in the source of fat; Megalac (high in C16 : 0), formaldehyde treated whole linseed (high in C18 : 3 n-3) and a combination of formaldehyde treated whole linseed and fish oil (high in C20 : 5 n-3 and C22 : 6 n-3). The concentrates were offered at approximately 0·4 of total dry matter intake. Samples of m. longissimus thoracis from Holstein-Friesians contained higher total amounts of fatty acids (P < 0·05) than that of Welsh Blacks in neutral lipid, but the phospholipid fatty acid content was similar between the breeds. Over all treatments, the proportion of C18 : 3 n-3 was higher (P < 0·001) in muscle neutral lipid of Welsh Blacks and the proportions of C18 : 3 n-3 and C18 : 1 trans were higher (P < 0·05 and P < 0·001, respectively) in their subcutaneous adipose tissue. Feeding linseed increased the amounts of C18 : 3 n-3 and also C20 : 5 n-3 in muscle phospholipids suggesting chain elongation and desaturation of C18 : 3 n-3 had occurred. The concentration of C20 : 5 n-3 was significantly higher (P < 0·05) in muscle phospholipids of Welsh Blacks while no differences were found for C18 : 3 n-3 and C22 : 6 n–3. However, when expressed as a proportion of total fatty acids, both C20 : 5 n-3 and C18 : 3 n-3 were significantly higher (P < 0·001) in the Welsh Black phospholipids. These differences resulted in a significantly higher P : S ratio of the muscle total fat (P < 0·05) in the Welsh Black than in the Holstein-Friesian but P : S was not affected by diet. On the other hand, the n-6 : n-3 PUFA ratio was significantly lower in the Welsh Black, reflecting the higher n-3 PUFA content. This ratio was lower in the linseed and the mixed treatments for both breeds, reflecting higher delivery of n-3 PUFA from these diets. Fortification of the diet with sources of PUFA and exploiting breed differences offer the potential to develop systems to increase human intakes of n-3 PUFA in line with current nutritional recommendations.

Antioxidant Activity of Whey in a Salmon Oil Emulsion

Abstract: The antioxidant capabilities of whey in a Tween20 TM -stabilized salmon emulsion were investigatedWhey fractions inhibited formation of thiobarbituric acid reactive substances (TBARS) and lipid peroxides in a 10% salmon oil emulsion in the order of whey > high-molecular-weight (HMW) fraction > low-molecular-weightfraction Heating the HMW fraction exposed sulfhydryls, with optimum exposure at 80 °C Heating the HMW frac-tion above 80 °C increased antioxidant activity The HMW fraction of whey (80 °C) alone, a-tocopherol (40 ppm)alone, and their combination inhibited TBARS 59, 19 and 86%, respectively, at 21 d of storage Sulfhydryls oxidizedbefore a-tocopherol, suggesting that sulfhydryls are the primary antioxidant Results indicate that whey proteinscould be useful antioxidants in food emulsionsKeywords: lipid oxidation, fish oil, a-tocopherol, whey, sulfhydryls Introduction T HE HEALTH BENEFITS OF DIETARY OMEGA -3 ( W -3) FATTY ACIDS include reduced susceptibility to malignant tumors, protec-tion against heart disease, and improved brain and eye functionin infants (Simopoulos 1991; Innis 1991) It is of great interest tofood manufacturers to use v-3 fatty acids as physiologically func-tional ingredients to improve the nutritional profile of food prod-ucts However, oxidation of v-3 fatty acids is very rapid, thuscausing rapid flavor deterioration, loss of nutrients, and forma-tion of potentially toxic compounds (Kubow 1992; Frankel 1998)These problems have been major barriers to utilizing oils thatcontain high concentrations of v-3 fatty acids in foodsOxidative stability of v-3 fatty acids can be increased usingfree radical scavengers Tertiary-butylhydroquinone (TBHQ,002%) has been successfully employed to slow oxidation of men-haden oil for up to 40 days, compared to approximately 3 d forthe control (Farkas and others 1997) ty of skim milk, an observation that was partially attributed to ex-Alpha-Tocopherol and bu-tylated hydroxytoluene (BHT) alone or in combination increasedthe oxidative stability of octadecatetraenoic acid (ODTA), eicosa-pentaenoic acid (EPA), and docosahexaenoic acid (DHA), inhibit-ing malonaldehye (MA) formation upon addition of Fenton’s re-agent (Ogata and others 1996) Alpha-Tocopherol inhibited MAformation from ODTA and DHA 67 and 28 % respectively, buthad no activity toward EPA BHT inhibited MA formation fromODTA, DHA, and EPA 80, 58 and 93 %, respectively (Ogata andothers 1996) A combination of ascorbic acid (200 ppm) solubi-lized in lecithin reverse micelles and d-tocopherol (4000 ppm)was also tested for its ability to decrease autoxidation of sardineoil, with the carbonyl value of the control reaching 45 at day 36and the carbonyl value of the antioxidant-treated sample reach-ing 10 during the same period (Han and others 1997)If v-3 fatty acids are to be successfully incorporated into pro-cessed foods, it will most likely be in the form of a lipid disper-sion While lipid-soluble free radical scavengers may be effectivein minimizing oxidation for a limited amount of time in bulk oils,their effectiveness seems to be dependent on fatty acid type andthey are not likely to be effective for the shelf-life required formost processed foods In addition, the effectiveness of lipid-sol-uble free radical scavengers in oil-in-water emulsions can be dif-ferent if they partition into both the continuous phase and emul-sion droplet (Huang and others 1997) Therefore, if v-3 fatty acidoils are to be successfully utilized in food emulsions, additionalantioxidant hurdles must be utilized, such as continuous phasemetal chelators and free radical scavengersProteins are well known mediators of lipid oxidation A num-ber of antioxidative proteins and protein products exist, includ-ing soy and yeast protein hydrolysates (Bishov and Henick 1972and 1975), gelatin (Kawashima 1979), and blood plasma proteins(Wayner and others 1987; Halliwell 1988) Mechanisms of the an-tioxidative effects of proteins include chelation of prooxidanttransition metals by proteins such as lactoferrin (Gutteridge andothers 1981) and serum albumin (Meucci and others 1991) andfree radical scavenging by amino acid residues such as cysteineand tyrosine (Wayner and others 1987; Ostdal and others 1996)Taylor and Richardson (1980) explored the antioxidant activi-ty of heated skim milk in a methyl linoleate emulsion catalyzedby hemoglobin They found that heat treatment (70 to 130 °C ina silicone oil bath, up to 30 min) increased the antioxidant activi-posure of proteinaceous sulfhydryl groups Heat treatment re-sulted in an increase in reactive sulfhydryls (48 mM sulfhydrylswith no heat to 71 mM sulfhydryls after a 130 °C, 30 min heattreatment), but a decline in total sulfhydryls (146 mM sulfhydr-yls with no heat to 39 mM sulfhydryls after a 130 °C, 30 min heattreatment) Milk fractions were also evaluated, with both wheyand casein being antioxidative, although casein showed muchgreater activity The activity of casein was hypothesized to bemostly due to a physical binding of prooxidants, while the activi-ty of whey was thought to be chemical in nature While this studyyielded interesting results concerning the antioxidant capabili-ties of skim milk and whey, it is difficult to predict how milk couldimpact oxidation in food systems since the research of Taylor andRichardson did not use prooxidants typical of a food emulsion(for example, hemoglobin), nor did they use lipids (methyl li-noleate dispersion with Tween 80

Triglyceride-lowering effect of omega-3 LC-polyunsaturated fatty acids--a review.

Abstract: There is increasing evidence that serum triglycerides are a significant and independent risk factor for CVD. The aim of this report is to review recent literature pertinent to the triglyceride-lowering effect of omega-3 long chain polyunsaturated fatty acids (LC-PUFA). Animal data are not considered because they are difficult to extrapolate to the human situation. A large body of evidence derived from epidemiological studies and clinical trials has consistently demonstrated that this effect is dose-dependent and can be achieved by diet. The smallest amount of omega-3 LC-PUFA needed to significantly lower serum triglycerides appears to be approximately 1 g/day as provided by a fish diet. Use of fish oil administering as little as 0.21 g EPA and 0.12 g DHA per day significantly lowered serum triglycerides in hyperlipidemics. In normolipidemics, a daily intake of 0.17 g EPA and 0.11 g DHA, given as a fish oil supplement, induced a non-significant reduction of 22%. These findings must be considered as preliminary and warrant further research. Intake of omega-3 LC-PUFA is frequently reported to modestly increase LDL cholesterol. However, in normo- or slightly hyperlipidemic individuals who received omega-3 LC-PUFA for 4 months or longer, changes of LDL cholesterol were not significantly different from a placebo group. Both EPA and DHA lower serum triglycerides, but they may have a differential effect on lipoproteins. Intake of omega-3 LC-PUFA in the amount mentioned above is safe.

Shelf life and eating quality of beef from cattle of different breeds given diets differing in n-3 polyunsaturated fatty acid composition.

Abstract: Two experiments were conducted with 32 Charolais cross steers (experiment 1) and 36 Holstein-Friesian and Welsh Black steers (experiment 2) to examine the effects of dietary n-3 polyunsaturated fatty acids (PUFA ) and breed on meat quality. Diets were comprised of grass silage and a concentrate (60 : 40 on a dry-matter basis). Lipid in the concentrate provided 30 g/kg diet dry matter derived from either linseed, fish oil or linseed/fish oil (experiment 1); and linseed or linseed/fish oil (experiment 2). These n-3 PUFA sources were compared with Megalac, a saturated fatty acid control, in both experiments. Diets were offered for 120 days (experiment 1) and 90 days (experiment 2). Measurements of meat quality included fatty acid composition, lipid oxidation and colour during retail display (i.e. shelf life parameters) and eating quality assessed by a trained taste panel. The samples examined were sirloin (longissimus) steaks and minced beef burgers produced from the forequarter muscles infraspinatus, supraspinatus and triceps brachii. The fatty acid results showed that linseed increased the proportion of 18 : 3 n-3 (a -linolenic acid) in neutral lipid of the burgers and approximately doubled it in the phospholipid. Increased synthesis of 20 : 4 n-3 and 20 : 5 n-3 also occurred, raising their levels in the phospholipid. Fish oil doubled the proportions of 20 : 5 n-3 and 22 : 6 n-3, with the linseed/fish oil results intermediate between linseed and fish oil. The Welsh Blacks in experiment 2 had higher proportions of 18 : 3 n-3 in neutral lipid and higher proportions of 18 : 3 n-3, 20 : 5 n-3 and 22 : 5 n-3 in phospholipid. This showed a clear genetic effect on fatty acid composition. The fish oil diet in experiment 1 greatly increased lipid oxidation during retail display in both overwrapped loin steaks and burgers packed in a modified atmosphere. Values for lipid oxidation in the burgers were much higher than in the steaks due to the intimate mixing of phospholipid fatty acids and prooxidants. Lipid oxidation was also greater in the linseed/fish oil samples than controls in both experiments but was similar in linseed and controls. Colour oxidation also proceeded more rapidly in the fish oil samples in experiment 1 and tended to be faster in the linseed/fish oil groups in both experiments. Eating quality was affected by diet in experiment 1 — the fish oil samples eliciting higher scores for ‘fishy’ and ‘rancid’ than controls and having lower ‘overall liking’ scores. Steaks from animals given the linseed diet (with high 18 : 3 n-3 proportions) had the highest ‘overall liking’ scores in experiment 1 but the cattle given linseed for the shorter time in experiment 2 were not different from controls. Despite their different PUFA profile in muscle, Welsh Blacks had similar eating quality scores to Holstein-Friesians which deposited more neutral lipid (marbling fat) in muscle.