The effect of short-term diets rich in fish, red meat, or white meat on thromboxane and prostacyclin synthesis in humans

Effects of paternal arachidonic acid supplementation on offspring behavior and hypothalamus inflammation markers in the mouse

Arachidonic acid (AA) is involved in inflammation and plays a role in growth and brain development in infants. We previously showed that exposure of mouse sires to AA for three consecutive generations induces a cumulative change in fatty acid (FA) involved in inflammation and an increase in body and liver weight in the offspring. Here, we tested the hypothesis that paternal AA exposure changes the progeny's behavioral response to a proinflammatory insult, and asked whether tissue-specific FA are associated with that response. Male BALB/c mice were supplemented daily with three doses of AA for 10 days and crossed to non-supplemented females (n = 3/dose). Two-month-old unsupplemented male and female offspring (n = 6/paternal AA dose) were exposed to Gram-negative bacteria-derived lipopolysaccharides (LPS) or saline control two hours prior to open field test (OFT) behavioral analysis and subsequent sacrifice. We probed for significant effects of paternal AA exposure on: OFT behaviors; individual FA content of blood, hypothalamus and hypothalamus-free brain; hypothalamic expression profile of genes related to inflammation (Tnfa, Il1b, Cox1, Cox2) and FA synthesis (Scd1, Elovl6). All parameters were affected by paternal AA supplementation in a sex-specific manner. Paternal AA primed the progeny for behavior associated with increased anxiety, with a marked sex dimorphism: high AA doses acted as surrogate of LPS in males, realigning a number of OFT behaviors that in females were differential between saline and LPS groups. Progeny hypothalamic Scd1, a FA metabolism enzyme with documented pro-inflammatory activity, showed a similar pattern of differential expression between saline and LPS groups at high paternal AA dose in females, that was blunted in males. Progeny FA generally were not affected by LPS, but displayed non-linear associations with paternal AA doses. In conclusion, we document that paternal exposure to AA exerts long-term behavioral and biochemical effects in the progeny in a sex-specific manner.

Nutrition, Thrombosis, and Cardiovascular Disease

Previous studies reported an inverse association between healthy dietary patterns (such as Mediterranean diet) and the incidence of cardiovascular events. As the mechanism accounting for cardiovascular disease is prevalently due to the atherothrombosis, where a pivotal role is played by platelet activation, it would be arguable that diets with protective effects against cardiovascular disease exert an anti-atherothrombotic effect via inhibition of platelet activation. There are several and sparse typologies of studies, which investigated if single nutrients by diets recognized as having cardiovascular protection may exert an antithrombotic effect. The most investigated nutrients are key components of the Mediterranean diets such as fruits and vegetables, fish, olive oil, and wine; other diets with protective effects include nuts and cocoa. Here we summarize experimental and human interventional studies which investigated the antithrombotic effects of such nutrients in experimental models of thrombosis or analyzed biomarkers of clotting, platelet, and fibrinolysis activation in human; furthermore in vitro studies explored the underlying mechanism at level of several cell lines such as platelets or endothelial cells. In this context, we analyzed if nutrients affect simultaneously or separately clotting, platelet, and fibrinolysis pathways giving special attention to the relationship between oxidative stress and thrombosis as most nutrients are believed to possess antioxidant properties.

Biomarkers of meat and seafood intake: an extensive literature review

Meat, including fish and shellfish, represents a valuable constituent of most balanced diets. Consumption of different types of meat and fish has been associated with both beneficial and adverse health effects. While white meats and fish are generally associated with positive health outcomes, red and especially processed meats have been associated with colorectal cancer and other diseases. The contribution of these foods to the development or prevention of chronic diseases is still not fully elucidated. One of the main problems is the difficulty in properly evaluating meat intake, as the existing self-reporting tools for dietary assessment may be imprecise and therefore affected by systematic and random errors. Dietary biomarkers measured in biological fluids have been proposed as possible objective measurements of the actual intake of specific foods and as a support for classical assessment methods. Good biomarkers for meat intake should reflect total dietary intake of meat, independent of source or processing and should be able to differentiate meat consumption from that of other protein-rich foods; alternatively, meat intake biomarkers should be specific to each of the different meat sources (e.g., red vs. white; fish, bird, or mammal) and/or cooking methods. In this paper, we present a systematic investigation of the scientific literature while providing a comprehensive overview of the possible biomarker(s) for the intake of different types of meat, including fish and shellfish, and processed and heated meats according to published guidelines for biomarker reviews (BFIrev). The most promising biomarkers are further validated for their usefulness for dietary assessment by published validation criteria.

A brief history of meat in the human diet and current health implications

Anthropological investigations have confirmed many times over, through multiple fields of research the critical role of consumption of animal source foods (ASF) including meat in the evolution of our species. As early as four million years ago, our early bipedal hominin ancestors were scavenging ASFs as evidenced by cut marks on animal bone remains, stable isotope composition of these hominin remains and numerous other lines of evidence from physiological and paleo-anthropological domains. This ASF intake marked a transition from a largely forest dwelling frugivorous lifestyle to a more open rangeland existence and resulted in numerous adaptations, including a rapidly increasing brain size and altered gut structure. Details of the various fields of anthropological evidence are discussed, followed by a summary of the health implications of meat consumption in the modern world, including issues around saturated fat and omega-3 fatty acid intake and discussion of the critical nutrients ASFs supply, with particular emphasis on brain function.

Fish consumption and cardiovascular disease related biomarkers: A review of clinical trials

The purpose of this review is to collect and compare fish intervention studies. Prospective studies have outlined the beneficial effect of frequent fish consumption on cardiovascular incidents that is attributed to n-3 fatty acids incorporated in fish, mainly eicosapentaenoic (EPA), and docosahexaenoic (DHA) acids. This outcome triggered clinical trials to examine the effect of either fish intake or consumption of n-3 fatty acids via capsules on biomarkers related to cardiovascular disease (CVD). The absence of a recent review focusing on clinical trials regarding fish intake and not n-3 fatty acids supplements rendered necessary the composition of this article. In total, 28 studies on healthy volunteers were found to meet the inclusion criteria. With EPA and DHA intake varying between 0.03 to 5 g per day, biomarkers, such as triglycerides, high-density lipoprotein and platelet aggregation, tended to ameliorate when daily intake exceeded 1 g per day, while the most common inflammatory marker, C-reactive protein, was not affected. In all, fish consumption gives promising results; yet fish micronutrients, total diet fat, as well as other dietary habits may also affect biomarkers. Therefore, all these factors should be considered in future clinical trials in order for one to draw more reliable conclusions.

Arachidonic acid supplementation modulates blood and skeletal muscle lipid profile with no effect on basal inflammation in resistance exercise trained men

Arachidonic acid (ARA), an omega-6 polyunsaturated fatty acid (PUFA), is the metabolic precursor to the eicosanoid family of lipid mediators. Eicosanoids have potent pro-inflammatory actions, but also act as important autocrine/paracrine signaling molecules in skeletal muscle growth and development. Whether dietary ARA is incorporated into skeletal muscle phospholipids and the resulting impact on intramuscular inflammatory and adaptive processes in-vivo is not known. In the current study, resistance trained men (≥1 year) received dietary supplementation with 1.5g/day ARA (n=9, 24 ± 1.5 years) or placebo (n=10, 26 ± 1.3 years) for 4-weeks while continuing their normal training regimen. Plasma and vastus lateralis muscle biopsies were collected in an overnight fasted state at baseline and week 4. ARA supplementation increased plasma content of ARA and gamma-linolenic acid, while decreasing relative abundance of linoleic acid, eicosapentaenoic acid, and dihomo-gamma-linolenic acid. In skeletal muscle, ARA and dihomo-gamma-linolenic acid content increased, whereas alpha-linolenic-acid was reduced. Compared to placebo, ARA supplementation reduced circulating platelet and monocyte number, and decreased the mRNA expression of the immune cell surface markers; neutrophil elastase/CD66b and interleukin 1-beta, in peripheral blood mononuclear cells. In muscle, ARA supplementation increased mRNA expression of the myogenic regulatory factors; MyoD and myogenin, but had no effect on a range of immune cell markers or inflammatory cytokines. These data show that dietary ARA supplementation can rapidly and safely modulate plasma and muscle fatty acid profile and promote myogenic gene expression in resistance trained men, without a risk of increasing basal systemic or intramuscular inflammation.

Differential Effects of Cod Proteins and Tuna Proteins on Serum and Liver Lipid Profiles in Rats Fed Non-Cholesterol- and Cholesterol-Containing Diets

Fish muscles are classified into white and red muscles, and the chemical composition of the two fish muscles have many differences. Few reports have assessed the health-promoting functions of white fish muscle proteins (WFP) and red fish muscle proteins (RFP). We therefore evaluated the mechanisms underlying the alteration of lipid profiles and cholesterol metabolism following the intake of WFP prepared from cod and RFP prepared from light muscles of tuna. Male Wistar rats were divided into six dietary groups: casein (23%), WFP (23%), and RFP (23%), with or without 0.5% cholesterol and 0.1% sodium cholate. Compared to the WFP-containing diet, the RFP-containing diet supplemented with cholesterol and sodium cholate significantly increased serum and liver cholesterol contents. However, in the RFP groups, an alteration in cholesterol metabolism including an increased tendency to excrete fecal sterols and hepatic cholesterol 7α-hydroxylase was related to the reduction of hepatic cholesterol contents. This phenomenon might be related to the tendency of an increased food intake in RFP-containing diets. These results highlight the differential effects of WFP and RFP on serum and liver lipid profiles of Wistar rats fed non-cholesterol- or cholesterol-containing diets under no fasting condition.

Effect of dietary fat and omega-3 fatty acids on urinary eicosanoids and sex hormone concentrations in postmenopausal women: a randomized controlled feeding trial

Substantial evidence relates increased sex hormone concentrations with increased breast cancer risk. Varying omega-3 (n-3) fatty acid (FA) intake may lead to alterations in eicosanoid balance and changes in circulating sex hormones that reduce risk. To clarify effects of dietary fat and n-3 FA intake on breast cancer risk markers, circulating sex hormones and urinary eicosanoids were measured in response to controlled feeding of diets designed to increase plasma concentrations of n-3 FA. A controlled cross-over feeding trial in postmenopausal women was conducted using 3 diets: high fat (HF; 40% energy from fat), low fat (LF; 20% energy from fat), and low fat plus n-3 FA (LFn3; 20% of energy from fat plus 3% of energy from n-3 FA) in 8-wk feeding periods. Plasma phospholipid fatty acid n-3 increased with the LFn3 relative to HF and LF (P < 0.0001). Plasma estradiol increased by 51% with HF (P = 0.03). Urinary prostaglandin E metabolite increased with HF relative to LF (P = 0.02) and urinary 11-dehydro-thromboxane B(2) increased with HF (P = 0.01). These results do not support a role of n-3 FA in the reduction of sex hormone levels.

The differential effects of EPA and DHA on cardiovascular risk factors

Compelling evidence exists for the cardioprotective benefits resulting from consumption of fatty acids from fish oils, EPA (20:5n-3) and DHA (22:6n-3). EPA and DHA alter membrane fluidity, interact with transcription factors such as PPAR and sterol regulatory element binding protein, and are substrates for enzymes including cyclooxygenase, lipoxygenase and cytochrome P450. As a result, fish oils may improve cardiovascular health by altering lipid metabolism, inducing haemodynamic changes, decreasing arrhythmias, modulating platelet function, improving endothelial function and inhibiting inflammatory pathways. The independent effects of EPA and DHA are poorly understood. While both EPA and DHA decrease TAG levels, only DHA appears to increase HDL and LDL particle size. Evidence to date suggests that DHA is more efficient in decreasing blood pressure, heart rate and platelet aggregation compared to EPA. Fish oil consumption appears to improve arterial compliance and endothelial function; it is not yet clear as to whether differences exist between EPA and DHA in their vascular effects. In contrast, the beneficial effect of fish oils on inflammation and insulin sensitivity observed in vitro and in animal studies has not been confirmed in human subjects. Further investigation to clarify the relative effects of consuming EPA and DHA at a range of doses would enable elaboration of current understanding regarding cardioprotective effects of consuming oily fish and algal sources of long chain n-3 PUFA, and provide clearer evidence for the clinical therapeutic potential of consuming either EPA or DHA-rich oils.

Estimated macronutrient and fatty acid intakes from an East African Paleolithic diet

Our genome adapts slowly to changing conditions of existence. Many diseases of civilisation result from mismatches between our Paleolithic genome and the rapidly changing environment, including our diet. The objective of the present study was to reconstruct multiple Paleolithic diets to estimate the ranges of nutrient intakes upon which humanity evolved. A database of, predominantly East African, plant and animal foods (meat/fish) was used to model multiple Paleolithic diets, using two pathophysiological constraints (i.e. protein < 35 energy % (en%) and linoleic acid (LA) >1.0 en%), at known hunter-gatherer plant/animal food intake ratios (range 70/30-30/70 en%/en%). We investigated selective and non-selective savannah, savannah/aquatic and aquatic hunter-gatherer/scavenger foraging strategies. We found (range of medians in en%) intakes of moderate-to-high protein (25-29), moderate-to-high fat (30-39) and moderate carbohydrates (39-40). The fatty acid composition was SFA (11.4-12.0), MUFA (5.6-18.5) and PUFA (8.6-15.2). The latter was high in α-linolenic acid (ALA) (3.7-4.7 en%), low in LA (2.3-3.6 en%), and high in long-chain PUFA (LCP; 4.75-25.8 g/d), LCP n-3 (2.26-17.0 g/d), LCP n-6 (2.54-8.84 g/d), ALA/LA ratio (1.12-1.64 g/g) and LCP n-3/LCP n-6 ratio (0.84-1.92 g/g). Consistent with the wide range of employed variables, nutrient intakes showed wide ranges. We conclude that compared with Western diets, Paleolithic diets contained consistently higher protein and LCP, and lower LA. These are likely to contribute to the known beneficial effects of Paleolithic-like diets, e.g. through increased satiety/satiation. Disparities between Paleolithic, contemporary and recommended intakes might be important factors underlying the aetiology of common Western diseases. Data on Paleolithic diets and lifestyle, rather than the investigation of single nutrients, might be useful for the rational design of clinical trials.

Regular consumption ofn-3 fatty acid-enriched pork modifies cardiovascular risk factors

The long-chain (LC)n-3 PUFA content of pork, particularly DHA, can be increased by including 15 % PorcOmega®(a fortified tuna fishmeal product) in pig finisher diets. The aim of the present study was to see whether this enriched pork could deliver cardiovascular health benefits to consumers. In a double-blind intervention trial, thirty-three healthy adult volunteers (sixteen female and seventeen male) were randomised to consume eithern-3-enriched or regular (control) pork (a selection of five fresh cuts totalling 1000 g/week) for 12 weeks. Fasting blood samples were collected every 4 weeks and analysed for serum lipids, maximally stimulated thromboxane production and erythrocyte fatty acid composition. Then-3-enriched pork provided subjects with 1·3 g LCn-3 PUFA per week. Erythrocyte DHA levels rose 15 % in then-3 group and fell 5 % in the control group over 12 weeks (P = 0·001). Compared with the control group, serum TAG decreased to a greater extent in then-3 group (P = 0·02) and serum thromboxane production increased to a lesser extent (P = 0·004). Changes in the latter were inversely associated with changes in incorporation of DHA into erythrocytes (r − 0·54;P < 0·05). Thus the modest increases in LCn-3 PUFA intake resulting from regular consumption of enriched pork can improve cardiovascular risk factors.

Fatty acid composition of habitual omnivore and vegetarian diets

High-fat diets are implicated in the onset of cardiovascular disease (CVD), cancer, and obesity. Large intakes of saturated and trans FA, together with low levels of PUFA, particularly long-chain (LC) omega-3 (n-3) PUFA, appear to have the greatest impact on the development of CVD. A high n-6:n-3 PUFA ratio is also considered a marker of elevated risk of CVD, though little accurate data on dietary intake is available. A new Australian food composition database that reports FA in foods to two decimal places was used to assess intakes of FA in four habitual dietary groups. Analysis using the database found correlations between the dietary intakes of LC n-3 PUFA and the plasma phospholipid LC n-3 PUFA concentrations of omnivore and vegetarian subjects. High meat-eaters (HME), who consumed large amounts of food generally, had significantly higher LC n-3 PUFA intakes (0.29 g/d) than moderate meat-eaters (MME) (0.14 g/d), whose intakes in turn were significantly higher than those of ovolacto-vegetarians or vegans (both 0.01 g/d). The saturated FA intake of MME subjects (typical of adult male Australians) was not different from ovolacto-vegetarian intakes, whereas n-6:n-3 intake ratios in vegetarians were significantly higher than in omnivores. Thus, accurate dietary and plasma FA analyses suggest that regular moderate consumption of meat and fish maintains a plasma FA profile possibly more conducive to good health.

Oily fish reduces plasma triacylglycerols: a primary prevention study in overweight men and women

OBJECTIVE

Previous studies have demonstrated benefits of high-dose long-chain omega-3 polyunsaturated fatty acid (LC omega-3 PUFA) supplements on metabolic risk. Effects of increased dietary omega-3 PUFA, via oily fish and/or plant-derived omega-3 PUFAs, are less clear and may be modulated by the omega-6:omega-3 PUFA of the habitual diet. This study examined the effect on cardiovascular disease risk markers of reducing dietary omega-6:omega-3 PUFA by changes in linoleic acid:alpha-linolenic acid (LA:LNA) and/or increasing LC omega-3 PUFA. It tested whether decreases in LA:LNA modulate effects of LC omega-3 PUFA.

METHODS

One hundred forty-two subjects, recruited to a 24-wk randomized study, were assigned to a control group or one of four interventions. Intervention groups received two portions of oily fish (4.5 g eicosapentaenoic acid + docosahexanoic acid) or white fish (0.7 g eicosapentaenoic acid + docosahexanoic acid) per week, and replaced habitual household fats with ones high in sunflower (high LA:LNA) or rapeseed (low LA:LNA) oil.

RESULTS

Modest dietary manipulations of omega-6 and omega-3 PUFAs resulted in significant group x time interactions for serum triacylglycerols (TAGs; P = 0.05); at 24 wk the control and two oily fish groups showed lower TAG than did the white fish/sunflower group (P = 0.05). Reductions in TAG, associated with increased oily fish intakes, were maximized when combined with lower dietary LA:LNA. There were no significant changes in several other cardiovascular disease risk markers.

CONCLUSIONS

Two portions of oily fish per week led to significant reductions in TAG relative to consumption of two portions of white fish per week. Changes in TAG were maximized when combined with lower LA:LNA.

n-3 Fatty acids from fish or fish-oil supplements, but not alpha-linolenic acid, benefit cardiovascular disease outcomes in primary- and secondary-prevention studies: a systematic review

Studies on the relation between dietary n-3 fatty acids (FAs) and cardiovascular disease vary in quality, and the results are inconsistent. A systematic review of the literature on the effects of n-3 FAs (consumed as fish or fish oils rich in eicosapentaenoic acid and docosahexaenoic acid or as alpha-linolenic acid) on cardiovascular disease outcomes and adverse events was conducted. Studies from MEDLINE and other sources that were of > or =1 y in duration and that reported estimates of fish or n-3 FA intakes and cardiovascular disease outcomes were included. Secondary prevention was addressed in 14 randomized controlled trials (RCTs) of fish-oil supplements or of diets high in n-3 FAs and in 1 prospective cohort study. Most trials reported that fish oil significantly reduced all-cause mortality, myocardial infarction, cardiac and sudden death, or stroke. Primary prevention of cardiovascular disease was reported in 1 RCT, in 25 prospective cohort studies, and in 7 case-control studies. No significant effect on overall deaths was reported in 3 RCTs that evaluated the effects of fish oil in patients with implantable cardioverter defibrillators. Most cohort studies reported that fish consumption was associated with lower rates of all-cause mortality and adverse cardiac outcomes. The effects on stroke were inconsistent. Evidence suggests that increased consumption of n-3 FAs from fish or fish-oil supplements, but not of alpha-linolenic acid, reduces the rates of all-cause mortality, cardiac and sudden death, and possibly stroke. The evidence for the benefits of fish oil is stronger in secondary- than in primary-prevention settings. Adverse effects appear to be minor.

Erythrocyte omega-3 and omega-6 polyunsaturated fatty acids and preeclampsia risk in Peruvian women

OBJECTIVE

This case-control study was conducted in Lima, Peru, from June 1997 through January 1998 to assess whether alteration in maternal erythrocyte omega-3 (n-3) and omega-6 (n-6) fatty acids was associated with increased risk of preeclampsia.

METHODS

A total of 99 preeclampsia and 100 normotensive pregnant women were included. Maternal erythrocyte n-3 and n-6 fatty acids were determined using capillary gas chromatography/mass spectrometry and expressed as micromolar (mM) concentrations. We employed logistic regression procedures to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULT

n-3 fatty acids were consistently lower in preeclampsia cases than controls. After adjusting for confounders, the corresponding ORs for preeclampsia across decreasing quartiles of sum of long-chain n-3 fatty acids were 1.0, 3.3, 2.4, and 3.3, respectively (P=0.07 for trend). A similar pattern was observed for eicosapentenoic acid (20:5n-3, EPA) and docosahexenoic acid (22:6n-3, DHA). There was no clear evidence of an association between arachidonic acid (20:4n-6, AA) and preeclampsia risk, the ORs in successively lower quartiles were 1.0, 1.1, 1.0, and 1.5 (P=0.48 for trend). A similar pattern was seen for the sum of long-chain n-6 fatty acids.

CONCLUSION

In Peruvian women, low erythrocyte n-3 fatty acids appeared to be associated with an increased risk of preeclampsia.

Dietary n-6 and n-3 fatty acid balance and cardiovascular health

Epidemiological and clinical studies have established that the n-6 fatty acid, linoleic acid (LA), and the n-3 fatty acids, linolenic acid (LNA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) collectively protect against coronary heart disease (CHD). LA is the major dietary fatty acid regulating low-density lipoprotein (LDL)-C metabolism by downregulating LDL-C production and enhancing its clearance. Further, the available mass of LA is a critical factor determining the hyperlipemic effects of other dietary fat components, such as saturated and trans fatty acids, as well as cholesterol. By contrast, n-3 fatty acids, especially EPA and DHA, are potent antiarryhthmic agents. EPA and DHA also improve vascular endothelial function and help lower blood pressure, platelet sensitivity, and the serum triglyceride level. The distinct functions of these two families make the balance between dietary n-6 and n-3 fatty acids an important consideration influencing cardiovascular health. Based on published literature describing practical dietary intakes, we suggest that consumption of ~6% en LA, 0.75% en LNA, and 0.25% en EPA + DHA represents adequate and achievable intakes for most healthy adults. This corresponds to an n-6/n-3 ratio of ~6:1. However, the absolute mass of essential fatty acids consumed, rather than their n-6/n-3 ratio, should be the first consideration when contemplating lifelong dietary habits affecting cardiovascular benefit from their intake.

The effect of vegetarian diet, plant foods, and phytochemicals on hemostasis and thrombosis

Ischemic heart disease (IHD) is multifactorial with a complex etiology. Conventional risk factors including serum lipids account for less than one half of future IHD events. In the past few years, novel risk factors such as hemostatic and thrombotic factors contributing to the development and progression of IHD have been explored. Typically, diet is the first line of consideration in the prevention of IHD, but very little is known about the effect of diet and nutrients on hemostasis and thrombosis. Cross-sectional studies indicate that vegetarians may have a lower concentration of certain markers of hemostasis compared with nonvegetarians. Platelet aggregation, an index of thrombosis, appears to be higher among vegetarians than nonvegetarians, perhaps because of the lower intake of long-chain n-3 fatty acids among vegetarians. Monounsaturated-fat-rich plant foods may have a protective role in hemostasis and may explain in part the lower incidence of IHD in Mediterranean countries where residents consume a diet high in monounsaturated fatty acid. Finally, certain fruits and vegetables such as soy, garlic, and purple grapes may have antithrombotic effects, which may in part be due to the phytochemicals in these foods. Although this review suggests that a plant-based diet with sufficient n-3 fatty acids and certain fruits and vegetables may have a favorable impact on hemostasis and thrombosis, the evidence is neither sufficient nor conclusive at this time to warrant specific recommendations for the public. Clearly, much remains to be done in this area of investigation.

Bread enriched with microencapsulated tuna oil increases plasma docosahexaenoic acid and total omega-3 fatty acids in humans

The aim of this study was to determine the acute and chronic effects of low doses of long chain (LC) n-3 polyunsaturated fatty acids (PUFA) (<100 mg per day) on plasma LC n-3 PUFA levels using a novel delivery form; bread containing microencapsulated tuna oil (MTO). Six omnivores (three men and three women) participated in the acute study, which involved ingesting a prototype MTO bread containing approximately 80 mg of LC n-3 PUFA/four slices. Plasma triacylglycerol fatty acid compositions were measured after an overnight fast and postprandially at 2 and 4 h. In the chronic study, 10 vegetarian subjects (nine men and one woman) consumed MTO bread at six to eight slices/day (comprising 60 mg of LC n-3 PUFA) as the only dietary source of these PUFA for three weeks. Fasting plasma total and phospholipid fatty acid compositions were measured at baseline and endpoint. In the acute study, the proportions of 22:6 n-3 and total n-3 PUFA in plasma triacylglycerol were significantly increased (P < 0.05). In the chronic study, the proportions of 20:5 n-3, 22:5 n-3, 22:6 n-3, total n-3 PUFA in plasma, and 22:6 n-3 and total n-3 PUFA in plasma phospholipid fractions were significantly increased (P < 0.05) at the endpoint compared with the baseline. This study showed that a low dose of LC n-3 PUFA, consumed as MTO-enriched bread, was bioavailable, as measured by an increase in LC n-3 PUFA levels in the plasma of human subjects.

Effect of dietary fatty acids on the intestinal permeability of marker drug compounds in excised rat jejunum

The aim of this study was to explore the effects of diets containing saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and omega-3 and omega-6 polyunsaturated fatty acids (omega-3 and omega-6 PUFA, respectively) on the passive and active transport properties of rat jejunum using marker compounds. Rats were fed diets supplemented with 18.4% (w/w) lipid (4 groups) or standard rat chow (1 group) for a period of 30 days. At the end of the dietary period, mucosal scrapings were taken for the determination of membrane phospholipids, and the apparent jejunal permeability of radiolabelled marker compounds was determined using modified Ussing chambers. Changes in the phospholipid content of the brush border membrane reflected the different lipid content of the diets. The passive paracellular permeability of mannitol was not significantly affected by the fatty acid composition of the diet, although there was a trend toward decreased mannitol permeability in the rats fed both the omega-3 and omega-6 PUFA diets. In comparison, the transcellular diffusion of diazepam was reduced by 20% (P < 0.05) in rats fed diets supplemented with omega-3 and omega-6 PUFA. In the lipid-fed rats, the serosal to mucosal flux of digoxin, an intestinal P-glycoprotein substrate, was reduced by 20% (P < 0.05) relative to the chow-fed group, however there were no significant differences between the different lipid groups. The active absorption of D-glucose via the Na+-dependent transport pathway was highest in the SFA, MUFA and PUFA omega-3 dietary groups, intermediate in the low-fat chow group and lowest in the PUFA omega-6 group, and was positively correlated with short-circuit current. These studies indicate that dietary fatty acid changes can result in moderate changes to the active and passive transport properties of excised rat jejunum.

Cardiovascular risk factors in vegetarians. Normalization of hyperhomocysteinemia with vitamin B(12) and reduction of platelet aggregation with n-3 fatty acids

Hyperhomocysteinemia in association with vitamin B(12) deficiency, and increased platelet aggregation, probably due to dietary lack of n-3 fatty acids, constitute cardiovascular risk factors frequently observed in vegetarians. We tested if administration of vitamin B(12) normalizes the concentration of total plasma homocysteine, and if intake of eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) fatty acids modulates platelet function in a population of lactoovovegetarians. One week after a single intramuscular injection of cyanocobalamin (10000 microg) in 18 individuals, serum vitamin B(12) increased from 149+/-63 pg/mL to 532+/-204 pg/mL (p<0.0001) and total tHcy dropped from 12.4+/-4.7 to 7.9+/-3.1 micromol/L (p<0. 0001). Ten of fourteen of these vegetarians completed an 8-week supplementation with 700 mg/day of each eicosapentaenoic and docosahexaenoic acids. Increased incorporation of these fatty acids into plasma lipids was observed in all of them, together with a significant reduction in maximum percentage or slope of platelet aggregation with all the agonists tested (ADP, epinephrin, collagen, arachidonic acid). No significant change in bleeding time was observed after n-3 fatty acid trial. Supplementation with vitamin B(12) and n-3 fatty acids corrects hyperhomocysteinemia and reduces platelet reactivity to agonists in vegetarians. Whether this supplementation improves the already reduced cardiovascular morbidity and mortality associated with vegetarian diet has yet to be demonstrated.

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

BACKGROUND

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

OBJECTIVE

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

DESIGN

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

RESULTS

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

CONCLUSION

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

Assessment of the arachidonic acid content in foods commonly consumed in the American diet

Arachidonic acid (AA) is an extremely important fatty acid involved in cell regulation. When provided in the diet, it is cogently incorporated in membrane phospholipids and enhances eicosanoid biosynthesis in vivo and in vitro; however, controversy exists as to the levels of AA in food and in the diet. This study determined the amount of AA in cooked and raw portions of beef (rib eye), chicken (breast and thigh), eggs, pork (loin), turkey (breast), and tuna; it compared these results to values published in Agriculture Handbook No. 8 (HB-8). The cooked portions were prepared as described in HB-8. With the exception of chicken thigh and tuna, the levels of AA (w/w) in the selected foods analyzed were significantly higher, in general, than those values published in HB-8. The greatest differences were observed in beef (raw and cooked), turkey breast (raw and cooked), and pork (cooked) where AA levels were twice that of the values in HB-8. In contrast, the AA and n-3 fatty acid contents in tuna were almost half the HB-8 values. The present data indicate that HB-8 tends to underreport the amounts of AA in a number of foods commonly consumed in the American diet, and new initiatives should be considered to validate and update the current database for fatty acid composition of foods.

Contribution of meat fat to dietary arachidonic acid

Arachidonic acid (AA) in the diet can be efficiently absorbed and incorporated into tissue membranes, resulting in an increased production of thromboxane A2 by platelets and increased ex vivo platelet aggregability. Results from previous studies have shown that AA is concentrated in the membrane phospholipids of lean meats. However, the concentration of AA in the visible fat portion of meats also may be significant despite being ignored in most studies. The aim of this study was to accurately quantitate the AA content of visible fat and the lean portion of beef, lamb, pork, chicken, duck, and turkey. The visible fat of meat contained a significant quantity of AA, ranging from 20 to 180 mg/100 g fat, whereas the AA content of the lean portion of meat was lower, ranging from 30 to 99 mg/100 g lean meat. Beef and lamb meats contained lower levels of AA in both the visible fat and lean portion than that from the other species. The highest level of AA in lean meat was in duck (99 mg/100 g), whereas pork fat had the highest concentration for the visible fats (180 mg/100 g). The lean portions of beef and lamb contained the higher levels of n-3 polyunsaturated fatty acids (PUFA) compared with white meats which were high in AA and low in n-3 PUFA. The present data indicate that the visible meat fat can make a contribution to dietary intake of AA, particularly for consumers with high intakes of fat from pork or poultry meat.