Practical applications of fish oil (Omega-3 fatty acids) in primary care

BACKGROUND: Fish oil (Omega-3 fatty acids) has been studied for more than 30 years. However, recent concerns of mercury and environmental toxins have clouded fish oil's potential clinical benefits. This article aims to review practical, evidence-based applications of fish oil for the primary care physician. METHODS: PubMed search using key words 'fish oil,' 'docosahexaenoic,' and 'eicosapentaenoic' in title/abstract. Limited to human clinical trials. Articles were further scanned for relevant sources. RESULTS: For secondary prevention of cardiovascular disease, 1 g of fish oil has shown to reduce overall and cardiovascular mortality, myocardial infarction, and sudden cardiac death. Higher doses may be used for its potent triglyceride-lowering effects and for patients with rheumatoid arthritis to reduce nonsteroidal anti-inflammatory use. Omega-3 fatty acid supplementation of infant formula has shown benefit in infant neural growth and development. With the potential health benefits of fish, women of childbearing age should be encouraged to eat 1 to 2 low-mercury fish meals per week. CONCLUSIONS: Fish oil has numerous practical applications for the primary care physician. Understanding the diverse clinical research of Omega-3 fatty acids and fish oil is important in determining its role in primary care practices.     

Plasma cholesterol responsiveness to saturated fatty acids

The variability in responsiveness to saturated fatty acids has not been studied systematically. For this reason data from three dietary studies carried out in our laboratory were pooled and used to evaluate how individuals vary in their responses in plasma concentrations of total cholesterol and low-density-lipoprotein cholesterol to the substitution of saturated fatty acids for unsaturated fatty acids. The data showed a marked variability in response. Some patients demonstrated a striking rise in cholesterol levels whereas others had more modest increases. This finding points to the need for further investigation on this issue.     

Influence of fish oil on ruminal biohydrogenation of C18 unsaturated fatty acids

Dietary cis-9, trans-11-conjugated linoleic acid (CLA) is generally thought to be beneficial for human health. Fish oil added to ruminant diets increases the CLA concentration of milk and meat, an increase thought to arise from alterations in ruminal biohydrogenation of unsaturated fatty acids. To investigate the mechanism for this effect, in vitro incubations were carried out with ruminal digesta and the main biohydrogenating ruminal bacterium, Butyrivibrio fibrisolvens. Linoleic acid (LA) or alpha-linolenic acid (LNA) was incubated (1.67 g/l) with strained ruminal digesta from sheep receiving a 50:50 grass hay-concentrate ration. Adding fish oil (up to 4.17 g/l) tended to decrease the initial rate of LA (P=0.025) and LNA (P=0.137) disappearance, decreased (P<0.05) the transient accumulation of conjugated isomers of both fatty acids, and increased (P<0.05) the accumulation of trans-11-18:1. Concentrations of EPA (20:5n-3) or DHA (22:6n-3), the major fatty acids in fish oil, were low (100 mg/l or less) after incubation of fish oil with ruminal digesta. Addition of EPA or DHA (50 mg/l) to pure cultures inhibited the growth and isomerase activity of B. fibrisolvens, while fish oil had no effect. In contrast, similar concentrations of EPA and DHA had no effect on biohydrogenation of LA by mixed digesta, while the addition of LA prevented metabolism of EPA and DHA. Neither EPA nor DHA was metabolised by B. fibrisolvens in pure culture. Thus, fish oil inhibits ruminal biohydrogenation by a mechanism which can be interpreted partly, but not entirely, in terms of its effects on B. fibrisolvens.     

Enrichment of spreadable fats with polyunsaturated fatty acids omega-3 using fish oil

Polyunsaturated fatty acids of the omega-3 series, especially very long chain--eicosapenta- and docosahexaenoic acid (EPA, DHA)--exert a strongly desirable influence on health. However, their intake with the western-style diet is usually too low which favours development of many diseases (CVD, cancers, allergies, etc.). Nowadays elevation of EPA and DHA intake is commonly recommended, but almost the only dietary source of them is seafoods, especially fish. A new way to increase the intake of long-chain omega-3 without radical changes of eating patterns is enrichment of regularly consumed foods with unhydrogenated fish oil. The aim of this study was to establish sensory and nutritionally acceptable enrichment level of low-calorie spreadable fats (soft margarine and mix of butter and vegetable oil) with EPA and DHA by addition of fish oil preparations (ROPUFA--30% EPA, DHA and MARITEX--10%), and evaluation of the stability of enriched spreads during storage (sensory and chemical). It was shown that tested spreadable fats might be enriched up to 1% EPA, DHA (i.e. 3% ROPUFA, 8% MARITEX), and that this had no significant influence on sensory acceptability. Both used fish oils which exerted similar influence on the quality of fats. An enriched mix of butter and vegetable oil and margarine may be stored up to 3 and 6 weeks respectively without significant decrease of quality. Peroxide value and acid numbers were not much affected by enrichment and storage. Daily portion (25-30 g/day) of spreadable fats enriched on the level established in the study may provide 0.2-0.3 g EPA, DHA, significantly increasing the amount of long-chain omega-3 in the diet above those eaten normally.     

Enrichment of spreadable fats with polyunsaturated fatty acids omega-3 using fish oil

Polyunsaturated fatty acids of the omega-3 series, especially very long chain – eicosapenta- and docosahexaenoic acid (EPA, DHA) – exert a strongly desirable influence on health. However, their intake with the western-style diet is usually too low which favours development of many diseases (CVD, cancers, allergies, etc.). Nowadays elevation of EPA and DHA intake is commonly recommended, but almost the only dietary source of them is seafoods, especially fish. A new way to increase the intake of long-chain omega-3 without radical changes of eating patterns is enrichment of regularly consumed foods with unhydrogenated fish oil. The aim of this study was to establish sensory and nutritionally acceptable enrichment level of low-calorie spreadable fats (soft margarine and mix of butter and vegetable oil) with EPA and DHA by addition of fish oil preparations (ROPUFA – 30% EPA, DHA and MARITEX – 10%), and evaluation of the stability of enriched spreads during storage (sensory and chemical). It was shown that tested spreadable fats might be enriched up to 1% EPA, DHA (i.e. 3% ROPUFA, 8% MARITEX), and that this had no significant influence on sensory acceptability. Both used fish oils which exerted similar influence on the quality of fats. An enriched mix of butter and vegetable oil and margarine may be stored up to 3 and 6 weeks respectively without significant decrease of quality. Peroxide value and acid numbers were not much affected by enrichment and storage. Daily portion (25–30 g/day) of spreadable fats enriched on the level established in the study may provide 0.2–0.3 g EPA, DHA, significantly increasing the amount of long-chain omega-3 in the diet above those eaten normally.     

鱼油类保健品中不饱和脂肪酸的气相色谱及质谱检测研究

[目的 ]　研究鱼油中多不饱和脂肪酸含量的确证分析方法。　 [方法 ]　利用毛细管气相色谱以及气质联用技术检测鱼油中多不饱和脂肪酸 (如DHA、EPA、DPA)的含量。　 [结果 ]　建立了用毛细管色谱柱进行有效分离 ,保留时间定性 ,以面积归一法或外标法定量 ,以GC -MS法进行确证的有效方法 ,同时对标准质谱库 (NIST库 )中没有的成分 (如DPA、DHA)建立了标准谱图。　 [结论 ]　本方法能满足对鱼油产品中不饱和脂肪酸的分析要求 ,具有简便、快速、可靠的特点     

Erythrocyte saturated fatty acids and systemic inflammation in adults

ObjectiveThe role of saturated fatty acids (SFAs) in chronic disease remains controversial; inflammation is one pathway by which SFAs influence the risk for chronic disease. The aim of this study was to investigate the associations between red blood cell (RBC) phospholipid SFAs and systemic inflammation.MethodsAs part of a randomized controlled trial, we measured RBC phospholipid FA composition in 55 generally healthy adults twice at 3-mo intervals. We estimated associations of RBC total SFAs and two major SFA subtypes, palmitic and stearic acids, with C-reactive protein (CRP), interleukin (IL)-6, white blood count (WBC), and a composite inflammation measure using generalized estimating equations in multivariable FA substitution models.ResultsMean (±SD) SFA level across both visits was 45% ± 3% of the total RBC FAs, mainly palmitic (21% ± 1%) and stearic (17% ± 3%) acids. In models adjusted for age, sex, race, smoking, body mass index, statin use, aspirin use, transunsaturated FAs, and ω-3 FAs, SFAs were significantly associated with IL-6 (20% increase per 1 SD increment; 95% confidence interval [CI], 0.03%–43%; P = 0.05) and the composite inflammation measure (P = 0.05) and marginally associated with CRP (34% increase; 95% CI, −1% to 81%; P = 0.06), but not associated with WBC. Stearic acid was positively associated with CRP (35% increase; 95% CI, 2%–79%; P = 0.04). Palmitic acid was marginally associated with the composite inflammation measure (P = 0.06) and, upon additional ω-6 FA adjustment, significantly associated with IL-6 (15% increase; 95% CI, 0.4%–27%; P = 0.006).ConclusionsRBC SFAs, which represent longer-term dietary intake, are positively associated with inflammation. In particular, palmitic acid was associated with IL-6, and stearic acid was associated with CRP after multivariable adjustment.     

Trans monounsaturated fatty acids and saturated fatty acids have similar effects on postprandial flow-mediated vasodilation

OBJECTIVE: Several studies suggest that a fatty meal impairs flow-mediated vasodilation (FMD), a measure of endothelial function. We tested whether the impairment was greater for trans fats than for saturated fats. We did this because we previously showed that replacement of saturated fats by trans fats in a controlled diet decreased FMD after 4 weeks. DESIGN: We fed 21 healthy men two different test meals with 0.9-1.0 g fat/kg body weight in random order: one rich in saturated fatty acids (Sat), mainly from palm kernel fat, and one rich in trans fatty acids (Trans) from partially hydrogenated soy bean oil. The study was performed in our metabolic ward. We had complete data for both diets of 21 men. RESULTS: FMD increased from a fasting value of 2.3+/-2.0% of the baseline diameter to 3.0+/-1.7% after the Sat test meal (95% CI for change -0.33, 1.70) and from 2.7+/-2.3 to 3.1+/-2.0% after the Trans test meal (95% CI for change -0.57, 1.29). The increase after the Sat meal was 0.22 (-1.18-1.61) FMD% higher than after the Trans meal. Serum triacylglycerols increased by 0.46+/-0.36 mmol/l after the Sat test meal and by 0.68+/-0.59 mmol/l after the Trans test meal; a difference of 0.23 (0.07, 0.39) mmol/l. Serum HDL-cholesterol was hardly affected by the test meals. The activity of serum paraoxonase, an esterase bound to HDL, increased slightly after the two test meals but the difference between meals was not significant. CONCLUSION: FMD was not impaired and not different after test meals with saturated or trans fatty acids. Thus, differences in long-term effects of these fats are not caused by differences in acute effects on the vascular wall.     

Effect of dietary n-3 fatty acids on the composition of long- and very-long-chain polyenoic fatty acid in rat retina

The effect of dietary supplementation with n-3 fatty acids, primarily docosahexaenoic acid (DHA) with high purity, on the fatty acid composition, especially very-long-chain fatty acids (VLCFA) longer than DHA, with four or six double bonds, in the rod outer segment (ROS) membranes of young Sprague-Dawley rats was investigated. After several weeks of feeding, diets high in n-3 fatty acids increased the DHA level significantly, while there were decreased levels of most n-6 fatty acids, such as arachidonic acid and 22:5n-6. Six kinds of VLCFA were detected by gas chromatography-mass spectrometry (GC-MS). Feeding a high n-3 fatty acid diet significantly increased the content of some n-3 VLCFAs such as 26:4n-3 and 30:4n-3 in ROS membranes, but not all detected n-3 VLCFAs. This study demonstrates that the dietary level of n-3 fatty acids not only affects the level of DHA, but also the levels of VLCFA in ROS membranes.     

Effects of dietary fish oil on fatty acids and eicosanoids in metastasizing human breast cancer cells

We examined the relationships between the suppressive effects of dietary fish oil on growth and metastasis of MDA-MB-435 human breast cancer cells in female nude mice and the primary tumor phospholipid fatty acid concentrations, phospholipase A2 activity, and eicosanoid levels. Mice (n = 120) were fed a 23% (wt/wt) corn oil (CO) linoleic acid (LA)-rich diet for seven days before and after 10(6) tumor cells were injected into a mammary fat pad, and then the mice receive one of three isocaloric diets containing 23% total fat but different proportions of CO and menhaden oil (MO) (18% CO-5% MO, 11.5% CO-11.5% MO, 5% CO-18% MO) or a 23% fat diet containing 18% deodorized fish oil supplemented with tocopherol and tert-butylhydroquinone antioxidants (FAO). Primary tumor growth rate was significantly greater in mice fed the 18% CO diet than in the three diets containing higher levels of fish oil (all p < 0.05). The 18% MO diet, but not the 11.5% MO or the 18% FAO diet, suppressed the development of lung metastases compared with the 18% CO diet. Increasing the proportion of MO relative to CO in the diets produced corresponding increases in the primary tumor phospholipid eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) concentrations and reductions in LA and arachidonic acid. There was a significant positive correlation between the LA concentration in these tumors and the extent of lung metastasis (r = 0.504). Tumor phospholipase A2 activity was unaffected by dietary MO intake. Prostaglandin E2 concentration was inversely correlated with phospholipid EPA (r = -0.484) and DHA (r = -0.439), but there was no relationship with lung metastasis. Tumor leukotriene B4 and 5-hydroxyeicosatetraenoic acid levels were not reduced by dietary MO. The 18% FAO- and the 18% MO-fed mice showed similar relationships for the phospholipid fatty acids and prostaglandin E2, despite the lack of effect on metastasis. The strong correlation between phospholipid LA levels and metastasis and the lack of an association with tumor eicosanoids suggest that the 18% MO diet inhibited metastasis because dietary LA was replaced by other fatty acids.     

Administration of low doses of fish oil derived N-3 fatty acids to elderly subjects

OBJECTIVES: To assess the incorporation of n-3 polyunsaturated fatty acids (PUFA) in plasma and erythrocyte lipids of elderly subjects after ingestion of very low doses of fish oil. The effects on alpha-tocopherol and retinol concentrations were also studied. SETTING: Municipal nursing home in Barcelona, Spain. SUBJECTS: Forty-five elderly subjects aged 60-92 y. DESIGN AND INTERVENTION: Subjects received a non-commercialized milk formula containing 1% fish oil for 15 months, which provided 0.40 g/d of n-3 PUFA. Fatty acid profiles and antioxidant concentrations were measured before and after the intervention period. RESULTS: Fish oil ingestion was associated with significant increases in total n-3 PUFA in plasma and erythrocytes by 32% and 18%, respectively. Eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid concentrations were higher after the ingestion period both in plasma and erythrocytes (P < 0.05), whereas linoleic and arachidonic acids remained unchanged. The n-6/n-3 ratio decreased by 21% in plasma and by 16% in erythrocytes (P < 0.05). Moreover, younger subjects showed a greater incorporation of EPA and DHA than older subjects. Plasma alpha-tocopherol and retinol concentrations did not vary significantly, whereas erythrocyte alpha-tocopherol was significantly higher after the intervention period. CONCLUSION: This study shows that low doses of n-3 PUFA supplemented with adequate amounts of alpha-tocopherol can be incorporated into blood lipids in elderly subjects without lowering their antioxidant concentrations.     

鱼油脂肪乳治疗脑外伤后SIRS的临床研究

目的:观察鱼油脂肪乳治疗脑外伤后全身炎症反应综合征(SIRS)的临床疗效,并探讨其可能机制。方法:将148例脑外伤后并发SIRS病人随机分为治疗组和对照组,每组74例。两组除给予常规临床处理外,治疗组给予20%脂肪乳250 ml+鱼油脂肪乳10 g静脉滴注;对照组给予20%脂肪乳250 ml,1次/d,共10 d。观察两组病人治疗前后急性生理学和慢性健康状况评分(APACHEⅡ)、多器官功能障碍综合征(MODS)发生率和病死率,并测定治疗前后血C-反应蛋白(CRP)水平。结果:治疗后两组病人APACHEⅡ评分明显降低。两组MODS发生率和病死率均有显著差异(P0.05)。鱼油脂肪乳治疗组病人CRP浓度明显低于对照组(P0.01)。结论:鱼油脂肪乳治疗脑外伤后SIRS的临床疗效显著,对稳定病人早期生命体征和降低脑外伤病死率的作用较好。     

Sources of the very-long-chain unsaturated omega-3 fatty acids: eicosapentaenoic acid and docosahexaenoic acid

PURPOSE OF REVIEW: We assess the toxicological, environmental and economic aspects of sources of fish oil and omega-3 fatty acids (n-3 fatty acids). RECENT FINDINGS: Fish oils are the most common source of the very-long-chain n-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid, which have protective and beneficial effects on conditions such as cardiovascular, inflammatory, or neurological diseases. Fish oils can also be potential hazards for human health, because of external pollutants bio-accumulating in fish. Wild and farmed fish are generally both similar in n-3 fatty acid content but may vary in terms of potential toxins. Reports on aquaculture and fish oil production, and other sources of n-3 fatty acids, are reviewed to assess which may be more suitable economically and ecologically for higher fish oil production and availability. SUMMARY: Although today's fish oil production meets demand, it is likely that this will not be able to increase without adversely affecting the world's wild stock of fish. Neither wild nor farmed fish constitute a sustainable source of n-3 fatty acids for supplementation. Solutions may be found through the evolution of the current aquaculture system or the utilization of alternative manufacturing sources for increasing intakes of n-3 fatty acids.     

Substitution of dietary monounsaturated fatty acids for saturated fatty acids in a free-living population: a feasibility study

The fatty acid composition of the diet of seven free-living subjects (five men and two women) aged 41–56 years was altered for 1 month. The aim was to increase the intake of monounsaturated fatty acids (MUFAs) from subjects current habitual levels of 12% dietary energy to a target intake of 18% dietary energy, and to decrease saturated fatty acid (SFA) from habitual levels of 16% dietary energy to target levels of 10% dietary energy. The change in fatty acid intake was achieved by supplying volunteers with foods prepared using MUFA-containing spreads or olive oil (ready meals, sweet biscuits and cakes) and also by supplying spreads, cooking oil and MUFA-enriched milk for domestic use. Body weight and plasma total cholesterol measurements were made at baseline and at 2 and 4 weeks on the diet as an aid to maintaining subject compliance. MUFA consumption was significantly increased from 12% dietary energy to 16% dietary energy ( P <0.01), and SFA intake was reduced from 16% dietary energy to 6% dietary energy ( P <0.01) during the 4-week intervention. The diet failed to achieve the target increase in MUFA but exceeded the target reduction in SFA. This was due to the fact that subjects reduced their total fat intake from a mean habitual level of 38% dietary energy to a mean level of 30% dietary energy. During the dietary period, mean plasma cholesterol levels were lower at 2 weeks ( P <0.01) and at 4 weeks ( P <0.01) than the baseline, with a mean reduction of 20% over the dietary period. This study demonstrates the difficulty of achieving increased MUFA intakes (by SFA substitution) in free-living populations when only a limited range of fatty-acid modified food products are provided to volunteers.