Low Omega-3 Research Articles

Benefit and Risk of Fish Consumption: Bio-Monitoring of Methylmercury Concentrations and Omega 3 Fatty Acid Contents Related to Habitual Fish Intake of French Pregnant Women

P-417 Abstract: Fish is a good source of important nutrients which are related to nutritional benefits. Fish is a predominant source of polyunsaturated fatty acids and is low in saturated fatty acids. It is well-known that omega-3 fatty acids appear to confer multiple human health benefit like reduction of depressive symptoms. Accumulating evidence suggest an association between a low omega-3 fatty acids status after pregnancy and the occurrence of postpartum depression. Nevertheless, due to environmental pollution, some fish species may contain high level of heavy metals and in particular of methylmercury. During perinatal period, pregnant women who consumed contaminated fish may be exposed to high concentrations of methylmercury that may contribute to subtle alterations of central nervous system in unborn baby and young children. The objective of our study is a) to evaluate the omega 3 fatty acid status of French pregnant women who consumed fish and seafood products and b) to examine the methylmercury exposure related to the consumption of fish and seafood of French pregnant women. One hundred and fifty pregnant women were recruited in this project. This research has started in October 2005 and the first results will be available in September 2006. As indicators of phospholipids contents, we used the phospholipids contents of cheek cells and red blood cells membrane. Cheek mucosal cells and red blood cells, obtained at the first and at the last trimester during pregnancy, were analyzed using gas chromatography. In addition, we used methylmercury concentration in hair as indicator of methylmercury exposure during pregnancy. Maternal hair sample were obtained at the first and at the last trimester during pregnancy and analyzed using flow-injection cold-vapor atomic absorption spectrometry. Moreover, habitual fish intake of the pregnant women was assessed using food frequency questionnaire including detailed information about consumption of different fish species and seafood (fresh, canned, smoked and cooked). The finality of this study was to examine the relationships between phospholipids contents, methylmercury and habitual fish intake of French pregnant women. To conclude, this clinical study could be a useful tool to highlight the discussion concerning the benefit versus risk ratio of fish consumption in concerned population.

ω−3 Fatty acid deficiency in major depressive disorder is caused by the interaction between diet and a genetically determined abnormality in phospholipid metabolism

Omega-3 fatty acids are a type of polyunsaturated fatty acid (PUFA). A growing body of evidence suggests that this form PUFA is a useful and well tolerated treatment for major depressive disorder, a common and serious mental illness. The efficacy of omega-3 PUFA is routinely explained as being due to a deficiency caused by inadequate dietary intake of this class of fatty acid. The hypothesis considered states that low omega-3 PUFA abundance in patients with major depressive and related disorders is due to an underlying genetically determined abnormality. The hypothesis can explain why although a specific and consistent deficit in omega-3, but not omega-6, PUFA occurs in major depressive and related disorders, the literature does not consistently support the notion that this is due to deficient dietary intake. Specifically it is hypothesized that having genetically determined low activity of fatty acid CoA ligase 4 and/or Type IV phospholipase A(2) combined with the low dietary availability of omega-3 PUFA results in reduced cellular uptake of omega-3 PUFA and constitutes a risk factor for depression. The hypothesis also has important consequences for the pharmacological treatment of depression in that it predicts that administering agents which enhance phospholipid synthesis, particularly those containing ethanolamine such as CDP-ethanolamine, should be effective antidepressants especially when co-administered with omega-3 PUFA.

Omega-3 fatty acid status in attention-deficit/hyperactivity disorder

Lower levels of long-chain polyunsaturated fatty acids, particularly omega-3 fatty acids, in blood have repeatedly been associated with a variety of behavioral disorders including attention-deficit/hyperactivity disorder (ADHD). The exact nature of this relationship is not yet clear. We have studied children with ADHD who exhibited skin and thirst symptoms classically associated with essential fatty acid (EFA) deficiency, altered plasma and red blood cell fatty acid profiles, and dietary intake patterns that do not differ significantly from controls. This led us to focus on a potential metabolic insufficiency as the cause for the altered fatty acid phenotype. Here we review previous work and present new data expanding our observations into the young adult population. The frequency of thirst and skin symptoms was greater in newly diagnosed individuals with ADHD ( n = 35 ) versus control individuals without behavioral problems ( n = 112 ) drawn from the Purdue student population. A follow up case-control study with participants willing to provide a blood sample, a urine sample, a questionnaire about their general health, and dietary intake records was conducted with balancing based on gender, age, body mass index, smoking and ethnicity. A number of biochemical measures were analyzed including status markers for several nutrients and antioxidants, markers of oxidative stress, inflammation markers, and fatty acid profiles in the blood. The proportion of omega-3 fatty acids was found to be significantly lower in plasma phospholipids and erythrocytes in the ADHD group versus controls whereas saturated fatty acid proportions were higher. Intake of saturated fat was 30% higher in the ADHD group, but intake of all other nutrients was not different. Surprisingly, no evidence of elevated oxidative stress was found based on analysis of blood and urine samples. Indeed, serum ferritin, magnesium, and ascorbate concentrations were higher in the ADHD group, but iron, zinc, and vitamin B6 were not different. Our brief survey of biochemical and nutritional parameters did not give us any insight into the etiology of lower omega-3 fatty acids, but considering the consistency of the observation in multiple ADHD populations continued research in this field is encouraged.

Evolutionary aspects of diet, the omega-6/omega-3 ratio and genetic variation: nutritional implications for chronic diseases

Anthropological and epidemiological studies and studies at the molecular level indicate that human beings evolved on a diet with a ratio of omega-6 to omega-3 essential fatty acids (EFA) of ~1 whereas in Western diets the ratio is 15/1 to 16.7/1. A high omega-6/omega-3 ratio, as is found in today's Western diets, promotes the pathogenesis of many diseases, including cardiovascular disease, cancer, osteoporosis, and inflammatory and autoimmune diseases, whereas increased levels of omega-3 polyunsaturated fatty acids (PUFA) (a lower omega-6/omega-3 ratio), exert suppressive effects. Increased dietary intake of linoleic acid (LA) leads to oxidation of low-density lipoprotein (LDL), platelet aggregation, and interferes with the incorporation of EFA in cell membrane phospholipids. Both omega-6 and omega-3 fatty acids influence gene expression. Omega-3 fatty acids have anti-inflammatory effects, suppress interleukin 1β (IL-1β), tumor necrosis factor-α (TNFα) and interleukin-6 (IL-6), whereas omega-6 fatty acids do not. Because inflammation is at the base of many chronic diseases, dietary intake of omega-3 fatty acids plays an important role in the manifestation of disease, particularly in persons with genetic variation, as for example in individuals with genetic variants at the 5-lipoxygenase (5-LO). Carotid intima media thickness (IMT) taken as a marker of the atherosclerotic burden is significantly increased, by 80%, in the variant group compared to carriers with the common allele, suggesting increased 5-LO promoter activity associated with the (variant) allele. Dietary arachidonic acid (AA) and LA increase the risk for cardiovascular disease in those with the variants, whereas dietary intake of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) decrease the risk. A lower ratio of omega-6/omega-3 fatty acids is needed for the prevention and management of chronic diseases. Because of genetic variation, the optimal omega-6/omega-3 fatty acid ratio would vary with the disease under consideration.

Effect of High Dietary Vitamin E on Lipid Stability of Oven-cooked and Hot-smoked Trout Fillets

Supplementing α-tocopheryl acetate (300 and 5000 mg/kg diet) in a trout finishing diet was done to minimize lipid oxidation in oven-cooked fillets and hot-smoked products. Hot-smoked processing did not affect α-tocopherol content of finished products compared with raw fillets. Feeding diets containing 5000 mg vitamin E/kg increased muscle α-tocopherol content that minimized lipid oxidation in (1) oven-cooked fillets produced from fresh and 7-d refrigerated fillets and (2) hot-smoked products following refrigerated storage for 8 wk. Dietary vitamin E did not affect fatty acid composition of products from either cooking method. Oven-cooked fillets produced from 7-d refrigerated, raw fillets and refrigerated, smoked products had lower percentages of omega-6 fatty acids and lower omega-3 fatty acids:omega-6 fatty acids ratios compared with fresh, raw samples.

Omega-3 Polyunsaturated Essential Fatty Acid Status as a Predictor of Future Suicide Risk

Low levels of docosahexaenoic acid, a polyunsaturated fatty acid, and elevated ratios of omega-6/omega-3 fatty acids are associated with major depression and, possibly, suicidal behavior. Predicting risk of future suicidal behaviors by essential fatty acid status merits examination. Plasma polyunsaturated fatty acid levels in phospholipids were measured in 33 medication-free depressed subjects monitored for suicide attempt over a 2-year period. Survival analysis examined the association of plasma polyunsaturated fatty acid status and pathological outcome. Seven subjects attempted suicide on follow-up. A lower docosahexaenoic acid percentage of total plasma polyunsaturated fatty acids and a higher omega-6/omega-3 ratio predicted suicide attempt. A low docosahexaenoic acid percentage and low omega-3 proportions of lipid profile predicted risk of suicidal behavior among depressed patients over the 2-year period. If confirmed, this finding would have implications for the neurobiology of suicide and reduction of suicide risk.

Levels of omega-3 fatty acid in serum phospholipids and depression in patients with lung cancer

Previous studies suggested that omega-3 fatty acids (FAs) have therapeutic effects against depression, but there is no evidence in the oncological setting. Our preliminary study reported the association between lower omega-3 FA intake and occurrence of depression in lung cancer patients. To explore the association further, the present study examined whether depression was associated with lower levels of omega-3 FAs in serum phospholipids. A total of 717 subjects in the Lung Cancer Database Project were divided into three groups by two cutoff points of the Hospital Anxiety and Depression Scale depression subscale (HADS-D). In all, 81 subjects of the nondepression and minor depression groups (HADS-D<5 and 5⩽HADS-D⩽10, respectively) were selected to match with 81 subjects of the major depression group (HADS-D>10) for age, gender, clinical stage, and performance status. Fatty acids were assayed by gas chromatography and compared among the three matched groups. There were no differences between the major depression group and nondepression group in any FAs. The minor depression group had higher mean levels of docosahexaenoic acid (mean±s.d. (%), nondepression: 7.40±1.54; minor depression: 7.90±1.40; major depression: 7.25±1.52, P=0.017). These results suggested that serum FAs are associated with minor, but not major, depression in lung cancer patients.

Role of Omega-3 Fatty Acids as a Treatment for Depression in the Perinatal Period

To consider the possible rationale and utility of omega-3 fatty acids as a treatment for depression in the perinatal period. A review of published and unpublished research was undertaken, using electronic databases, conferences proceedings and expert informants. Relevant bodies of evidence include an epidemiological link between low fish intake and depression. Laboratory studies show correlations between low omega-3 fatty acid levels and depression, as well as reduced levels of omega-3 in non-depressed women during the perinatal period. Treatment studies using omega-3 in patients with mood disorders further support an omega-3 contribution, as do neuroscientific theories. Research into omega-3 and infant development also highlights potential effects of depletion in the perinatal period and supports infant safety and benefits of supplementation. There is a relative lack of knowledge about the safety of standard antidepressants in the perinatal period. There is a clear need for more research into alternative treatments, such as omega-3 fatty acids, in the management of depression in the perinatal period.

Major depression is associated with lower omega-3 fatty acid levels in patients with recent acute coronary syndromes

Background Polyunsaturated fatty acids (PUFAs) are intrinsic cell membrane components and closely involved in neurotransmission and receptor function. Lower omega-3 levels are associated with increased risk of coronary artery disease (CAD), increases in cardiac events in CAD patients, and depression. We sought to examine relationships between depression and serum levels of omega-3 and omega-6 PUFAs in patients recovering from acute coronary syndromes (ACS). Methods We carried out a case-control study of serum PUFA levels and current major depression in 54 age- and sex-matched pairs approximately 2 months following ACS. Results Depressed patients had significantly lower concentrations of total omega-3 and docosahexaenoic acid (DHA), and higher ratios of arachidonic acid (AA) to DHA, AA to eicosapentaenoic acid (EPA), and n-3 to n-6 than controls. There were no baseline differences in any potential risk or protective factors for depression. Conclusions Results are consistent with previous reports in depressed patients without CAD, and with literature concerning omega-3 levels and risk of CAD events. Dietary, genetic, and hormonal factors may all play a role in both depression and CAD. Both prospective studies and randomized trials are needed to help clarify the interrelationships.

Fish consumption and depression: the Northern Finland 1966 birth cohort study

Background: Since low fish consumption and omega-3 fatty acids have recently been linked with depression, we investigated by means of a large, general population database, whether a low fish consumption is associated with increased risk of developing depression. Methods: The Northern Finland 1966 Birth Cohort was followed up prospectively from pregnancy up to the age of 31 years. The data on HSCL-25 depression subscale, doctor-diagnosed life-time depression and fish consumption (during the previous 6 months) of cohort members were obtained by postal questionnaires at the age of 31. The final number of cohort members, whose completed variable information was available in multivariate logistic analyses, was 2721 males and 2968 females. Results: After adjusting for body mass index, serum total cholesterol level and socioeconomic situation, logistic regression analyses showed that among females the risk of developing depression increased up to 2.6-fold (95%CI 1.4–5.1) among rare fish eaters when compared with regular eaters. In males, there were no significant differences between rare and regular fish eaters for any of the estimates of depression. Limitations: The data on life-time fish consumption of cohort members were not available. Conclusions: A low frequency of fish consumption was statistically significantly associated with depression in women, but not in men. Possible background-theories behind the gender difference are discussed.

Nutrition and schizophrenia: beyond omega-3 fatty acids

There are now five placebo-controlled trials of EPA in the treatment in schizophrenia, and four of these have given positive or partly positive findings. A cross-national ecological analysis of international variations in outcome of schizophrenia in relation to national dietary practices, showed that high consumption of sugar and of saturated fat is associated with a worse long-term outcome of schizophrenia. It is known that a high sugar, high fat diet leads to reduced brain expression of brain-derived neurotrophic factor (BDNF) which is responsible for maintaining the outgrowth of dendrites. Low brain BDNF levels also lead to insulin resistance which occurs in schizophrenia and is associated with diseases of the metabolic syndrome. It appears that the same dietary factors which are associated with the metabolic syndrome, including high saturated fat, high glycaemic load, and low omega-3 PUFA, may also be detrimental to the symptoms of schizophrenia, possibly through a common mechanism involving BDNF.

Omega-6/Omega-3 Essential Fatty Acid Ratio and Chronic Diseases

Several sources of information suggest that human beings evolved on a diet with a ratio of omega-6 to omega-3 essential fatty acids (EFA) of ∼1 whereas in Western diets the ratio is 15/1–16.7/1. Western diets are deficient in omega-3 fatty acids, and have excessive amounts of omega-6 fatty acids compared with the diet on which human beings evolved and their genetic patterns were established. Excessive amounts of omega-6 polyunsaturated fatty acids (PUFA) and a very high omega-6/omega-3 ratio, as is found in today's Western diets, promote the pathogenesis of many diseases, including cardiovascular disease, cancer, and inflammatory and autoimmune diseases, whereas increased levels of omega-3 PUFA (a lower omega-6/omega-3 ratio), exert suppressive effects. In the secondary prevention of cardiovascular disease, a ratio of 4/1 was associated with a 70% decrease in total mortality. A ratio of 2.5/1 reduced rectal cell proliferation in patients with colorectal cancer, whereas a ratio of 4/1 with the same amount of omega-3 PUFA had no effect. The lower omega-6/omega-3 ratio in women with breast cancer was associated with decreased risk. A ratio of 2-3/1 suppressed inflammation in patients with rheumatoid arthritis, and a ratio of 5/1 had a beneficial effect on patients with asthma, whereas a ratio of 10/1 had adverse consequences. These studies indicate that the optimal ratio may vary with the disease under consideration. This is consistent with the fact that chronic diseases are multigenic and multifactorial. Therefore, it is quite possible that the therapeutic dose of omega-3 fatty acids will depend on the degree of severity of disease resulting from the genetic predisposition. A lower ratio of omega-6/omega-3 fatty acids is more desirable in reducing the risk of many of the chronic diseases of high prevalence in Western societies, as well as in the developing countries, that are being exported to the rest of the world

The importance of the ratio of omega-6/omega-3 essential fatty acids

Several sources of information suggest that human beings evolved on a diet with a ratio of omega-6 to omega-3 essential fatty acids (EFA) of ∼ 1 whereas in Western diets the ratio is 15/1–16.7/1. Western diets are deficient in omega-3 fatty acids, and have excessive amounts of omega-6 fatty acids compared with the diet on which human beings evolved and their genetic patterns were established. Excessive amounts of omega-6 polyunsaturated fatty acids (PUFA) and a very high omega-6/omega-3 ratio, as is found in today’s Western diets, promote the pathogenesis of many diseases, including cardiovascular disease, cancer, and inflammatory and autoimmune diseases, whereas increased levels of omega-3 PUFA (a low omega-6/omega-3 ratio) exert suppressive effects. In the secondary prevention of cardiovascular disease, a ratio of 4/1 was associated with a 70% decrease in total mortality. A ratio of 2.5/1 reduced rectal cell proliferation in patients with colorectal cancer, whereas a ratio of 4/1 with the same amount of omega-3 PUFA had no effect. The lower omega-6/omega-3 ratio in women with breast cancer was associated with decreased risk. A ratio of 2–3/1 suppressed inflammation in patients with rheumatoid arthritis, and a ratio of 5/1 had a beneficial effect on patients with asthma, whereas a ratio of 10/1 had adverse consequences. These studies indicate that the optimal ratio may vary with the disease under consideration. This is consistent with the fact that chronic diseases are multigenic and multifactorial. Therefore, it is quite possible that the therapeutic dose of omega-3 fatty acids will depend on the degree of severity of disease resulting from the genetic predisposition. A lower ratio of omega-6/omega-3 fatty acids is more desirable in reducing the risk of many of the chronic diseases of high prevalence in Western societies, as well as in the developing countries, that are being exported to the rest of the world.

The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic.

Field studies of twentieth century hunter-gathers (HG) showed them to be generally free of the signs and symptoms of cardiovascular disease (CVD). Consequently, the characterization of HG diets may have important implications in designing therapeutic diets that reduce the risk for CVD in Westernized societies. Based upon limited ethnographic data (n=58 HG societies) and a single quantitative dietary study, it has been commonly inferred that gathered plant foods provided the dominant energy source in HG diets. In this review we have analyzed the 13 known quantitative dietary studies of HG and demonstrate that animal food actually provided the dominant (65%) energy source, while gathered plant foods comprised the remainder (35%). This data is consistent with a more recent, comprehensive review of the entire ethnographic data (n=229 HG societies) that showed the mean subsistence dependence upon gathered plant foods was 32%, whereas it was 68% for animal foods. Other evidence, including isotopic analyses of Paleolithic hominid collagen tissue, reductions in hominid gut size, low activity levels of certain enzymes, and optimal foraging data all point toward a long history of meat-based diets in our species. Because increasing meat consumption in Western diets is frequently associated with increased risk for CVD mortality, it is seemingly paradoxical that HG societies, who consume the majority of their energy from animal food, have been shown to be relatively free of the signs and symptoms of CVD. The high reliance upon animal-based foods would not have necessarily elicited unfavorable blood lipid profiles because of the hypolipidemic effects of high dietary protein (19-35% energy) and the relatively low level of dietary carbohydrate (22-40% energy). Although fat intake (28-58% energy) would have been similar to or higher than that found in Western diets, it is likely that important qualitative differences in fat intake, including relatively high levels of MUFA and PUFA and a lower omega-6/omega-3 fatty acid ratio, would have served to inhibit the development of CVD. Other dietary characteristics including high intakes of antioxidants, fiber, vitamins and phytochemicals along with a low salt intake may have operated synergistically with lifestyle characteristics (more exercise, less stress and no smoking) to further deter the development of CVD.

Keloids in rural black South Africans Part 2: dietary fatty acid intake and total phospholipid fatty acid profile in the blood of keloid patients

In the second part of this study, emphasis is placed on nutritional intakes (fatty acids and micronutrients) and fatty acid intake and metabolism in the blood, respectively, according to a combined 24 h recall and standardized food frequency questionnaire analyses of keloid prone patients (n=10), compared with normal black South Africans (n=80), and total phospholipid blood (plasma and red blood cell ) analyses of keloid patients (n=20), compared with normal individuals (n=20). Lipid extraction and fractionation by standard procedures, total phospholipid (TPL) separation with thin layer chromatography, and fatty acid methyl ester analyses with gas liquid chromatography techniques were used. Since nutrition may play a role in several disease disorders, the purpose of this study was to confirm or refute a role for essential fatty acids (EFAs) in the hypothesis of keloid formations stated in part 1 of this study.1According to the Canadian recommendation (1991), we observed that in keloid patients linoleic acid (LA) and arachidonic acid (AA) dietary intakes, as EFAs of the omega-6-series, are higher than the recommended 7–11 g/d. However, the a-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) dietary intakes, as EFAs of the omega-3 series, are lower than the recommendation of 1.1–1.5 g/d. This was also the case in the control group, where a higher dietary intake of the omega-6 fatty acids and a slightly lower dietary intake of the omega-3 fatty acids occurred. Thus, we confirm a high dietary intake of LA (as a product of organ meats, diary products and many vegetable oils) and AA (as a product of meats and egg yolks), as well as lower dietary intakes of ALA (as a product of grains, green leafy vegetables, soy oil, rapeseed oil and linseed), and EPA and DHA (as products of marine oils). Lower micronutrient intakes than the recommended dietary allowances were observed in the keloid group that may influence EFA metabolism and/or collagen synthesis. Of cardinal importance may be the lower intake of calcium in the keloid patients that may contribute to abnormal cell signal transduction in fibroblasts and consequent collagen overproduction, and the lower copper intake that may influence the immune system, or perhaps even the high magnesium intake that stimulates metabolic activity. Micronutrient deficiencies also occurred in the diets of the normal black South Africans that served as a control group. In the case of plasma TPLs, deficiency of the omega-3 EFA series (ALA, EPA and DHA) occurred, and this is in accordance with the apparent lower omega-3 EFA intake in the diets of these patients. In the case of the red blood cell TPLs, as a true and reliable source of dietary fatty acid intake and metabolism, sufficient EFAs of the omega-6 series (LA and AA) and the omega-3 series (ALA, EPA and DHA) occurred. For this study group a relative deficiency of nutritional omega-3 EFA intake apparently did occur, but was probably compensated for by blood fatty acid metabolism.

Effect of low dose omega-3 fatty acid on rectal mucosal cell proliferation in patients at high risk of colorectal cancer

Effect of low dose omega-3 fatty acid on rectal mucosal cell proliferation in patients at high risk of colorectal cancer

Triglyceride hydrolysis of soy oil vs fish oil emulsions.

Fish oil triglycerides (TG) are being considered for use in IV lipid emulsions, but the characteristics of their lipase-mediated clearance from plasma are largely unknown. We compared the in vitro hydrolysis of soy oil long-chain triglyceride emulsions (LCT) and fish oil emulsions (omega-3) using lipoprotein (LPL) and hepatic (HL) lipases, omega-3 emulsions contained 18% and 28% of total TG fatty acid as eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA), respectively. Under conditions of maximal hydrolysis, total free fatty acid (FFA) release was two- to threefold greater with LCT compared with omega-3 emulsions. Also, EPA and DHA together contributed proportionally much less than other fatty acids (< 20%) to FFA released from omega-3 emulsions. In mixtures of LCT emulsion with omega-3 emulsions, the presence of > 20% of omega-3 particles substantially inhibited LCT emulsion hydrolysis (by up to 50%). Our results suggest that, during infusion of omega-3 emulsions, EPA and DHA may enter cells as TG or partial glycerides within emulsion particles and not as FFA and that coinfusion of omega-3 emulsion with LCT emulsion at low omega-3:LCT emulsion ratios (up to 20% of total triglyceride as omega-3) will not substantially inhibit LCT hydrolysis.

Effect of a high omega-3 fatty acid diet on cardiac contractile performance in Oncorhynchus mykiss

Omega-3 fatty acids have been implicated in the amelioration of cardiovascular disease in humans. Since these fatty acids are found in salmonid fish and are known to be essential for all salmonids, this study was undertaken to determine the effect of a high dietary intake of omega-3 fatty acids on the function of trout myocardium. Rainbow trout (Oncorhynchus mykiss) from a single stock population were divided into two groups and fed either a diet high in omega-3 fatty acids (i.e. 4.0%) or low in omega-3 fatty acids (i.e. 2.1%) for 3 months. Heart function was studied at the whole heart and isolated muscle level. In whole heart preparations, peak developed pressures in freely ejecting hearts from salmonids fed the high omega-3 fatty acid diet were significantly greater than the hearts from salmonids fed the low omega-3 fatty acid diet (21 +/- 1.5 vs. 11.5 +/- 0.9 mmHg respectively, P < 0.05). These data correlated with results from isolated muscle preparations of myocardium from fish fed high and low omega-3 fatty acid diets (4.12 +/- 0.32 vs. 3.08 +/- 0.28 mN/mm2 respectively, P < 0.05). The calcium uptake rate of heart homogenates from fish fed the high omega-3 diet was slower and sarcoplasmic reticulum Ca2+ ATPase activity was lower. The myofilament force-calcium relationship in myocardium from trout fed the low omega-3 diet was shifted leftward on the calcium axis to lower intracellular calcium concentrations (delta 0.4 pCa units) compared to mammalian myocardium. This resulted in greater activation at lower intracellular calcium concentrations. However, trouts fed diets high in omega-3 fatty acids had [Ca2+] required for half maximal activation more similar to what has been reported for mammalian myocardium (delta 0.1 pCa unit). Furthermore, the myofilaments of trout hearts appear to show less cooperativity (Hill coefficient approximately 1) than has been found in mammalian myocardium (Hill coefficient > or = 2). Our experimental results demonstrate for the first time that dietary omega-3 fatty acid content affects myocardial force of contraction by affecting calcium metabolism and myofilament calcium-activation.

Relationship between dietary fatty acid, selenium, and degenerative cardiomyopathy.

With the finding of an increasing number of cases of degenerative cardiomyopathy (DCM) amongst patients in Chongqing, Sichuan, People's Republic of China, an attempt has been made to delineate possible etiological factors. In this province endemic for Keshan disease and with considerable consumption of oils high in erucic acid, the latter does not appear to be an operative noxious agent in DCM. Additionally, it does not appear to be caused by excessive oxygen radicals, low levels of antioxidants or low selenium levels. However, lower omega-3 fatty acid levels along with higher serum lipids may be the mechanism, via higher thromboxane levels, of the production of the myocardial degeneration seen in DCM.

INFLUENCE OF DIETARY OMEGA‐6, ‐3 FATTY ACID SOURCES ON THE INITIATION AND PROMOTION STAGES OF PHOTOCARCINOGENESIS

To determine the segment along the carcinogenic continuum at which dietary lipid exerts its principal effect, six groups of 35 Skh-HR-1 hairless mice were placed on defined isocaloric diets containing either 0.75%, 12% corn oil or 12% menhaden oil as sources of omega-6 or omega-3 fatty acids, respectively. All animals received an 11 week course of UV-radiation from fluorescent sunlamps. Upon termination of UV, diets of some groups were crossed-over to either low fat, high fat, omega-6 or omega-3 fatty acid sources. The first tumor appeared at week 14. Life-table analysis of the tumor incidence curves and Wilcoxon tests of tumor multiplicity provided evidence that high corn oil diets significantly (P less than 0.01) enhance carcinogenic expression; that tumor enhancement by the omega-6 fatty acid source occurs during the post-initiation, or promotion, stage; that replacement with a low corn oil diet after UV-initiation will negate the exacerbating effect of high corn oil; and that an omega-3 fatty acid source inhibits UV-carcinogenesis even at high dietary levels, although not during the post-initiation stage.