Fish oil increases peripheral capillary blood cell velocity in humans

The Physiological Effect of n-3 Polyunsaturated Fatty Acids (n-3 PUFAs) Intake and Exercise on Hemorheology, Microvascular Function, and Physical Performance in Health and Cardiovascular Diseases; Is There an Interaction of Exercise and Dietary n-3 PUFA Intake?

Physical activity has a beneficial effect on systemic hemodynamics, physical strength, and cardiac function in cardiovascular (CV) patients. Potential beneficial effects of dietary intake of n-3 polyunsaturated fatty acids (n-3 PUFAs), such as α-linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid on hemorheology, vascular function, inflammation and potential to improve physical performance as well as other CV parameters are currently investigated. Recent meta-analysis suggests no effect of n-3 PUFA supplementation on CV function and outcomes of CV diseases. On the other hand, some studies support beneficial effects of n-3 PUFAs dietary intake on CV and muscular system, as well as on immune responses in healthy and in CV patients. Furthermore, the interaction of exercise and dietary n-3 PUFA intake is understudied. Supplementation of n-3 PUFAs has been shown to have antithrombotic effects (by decreasing blood viscosity, decreasing coagulation factor and PAI-1 levels and platelet aggregation/reactivity, enhancing fibrinolysis, but without effects on erythrocyte deformability). They decrease inflammation by decreasing IL-6, MCP-1, TNFα and hsCRP levels, expression of endothelial cell adhesion molecules and significantly affect blood composition of fatty acids. Treatment with n-3 PUFAs enhances brachial artery blood flow and conductance during exercise and enhances microvascular post-occlusive hyperemic response in healthy humans, however, the effects are unknown in cardiovascular patients. Supplementation of n-3 PUFAs may improve anaerobic endurance and may modulate oxygen consumption during intense exercise, may increase metabolic capacity, enhance endurance capacity delaying the onset of fatigue, and improving muscle hypertrophy and neuromuscular function in humans and animal models. In addition, n-3 PUFAs have anti-inflammatory and anti-nociceptive effects and may attenuate delayed-onset muscle soreness and muscle stiffness, and preserve joint mobility. On the other hand, effects of n-3 PUFAs were variably observed in men and women and they vary depending on dietary protocol, type of supplementation and type of sports activity undertaken, both in healthy and cardiovascular patients. In this review we will discuss the physiological effects of n-3 PUFA intake and exercise on hemorheology, microvascular function, immunomodulation and inflammation and physical performance in healthy persons and in cardiovascular diseases; elucidating if there is an interaction of exercise and diet.

Omega-3 fatty acid levels in red blood cell membranes and physical decline over 3 years: longitudinal data from the MAPT study

Studies have shown that omega-3 polyunsaturated fatty acids (PUFAs) are associated with brain, cardiovascular, and immune function, as well as physical performance and bone health in older adults. So far, few studies have investigated the associations between PUFA status and performance-based tests of physical function. The objective of this study was to investigate the associations between the omega-3 PUFA levels (eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA)) in red blood cell (RBC) membranes and physical performance, in a sample of community-dwelling older adults. This is a longitudinal observational study using data from the Multidomain Alzheimer's Disease Trial (MAPT), a randomized, placebo-controlled trial. Four hundred participants from MAPT placebo group with available PUFA data were included. Omega-3 PUFA levels in RBC membranes were measured at baseline, and their percentage of total RBC membrane fatty acid content was calculated. We dichotomized the standardized omega-3 PUFA levels in RBC membranes as low (lowest quartile) vs. high (three upper quartiles). Gait speed (in m/s) and short physical performance battery (SPPB) score (range from 0 to 12, higher is better) were used to assess physical performance at baseline and after 6, 12, 24, and 36 months. Participants were 75.2 (± 4.3) years old and 68% were female. Bivariate analyses found that the characteristic of the participants in the lowest quartile of omega-3 PUFA levels (Q1) and those in the three upper quartiles (Q2-Q4) was not different at baseline; only those in Q1 were slightly older. In an unadjusted model, the difference in gait speed after 3 years of follow-up was significant (- 0.09 ± 0.03 m/s; p = 0.008) between participants in Q1 and those in Q2-Q4. In a model adjusted for age, gender, educational level, cognitive function, depressive status, body mass index, physical activity, grip strength, and their time interaction, this difference remained clinically relevant (- 0.07 ± 0.04 m/s; p = 0.075). No difference between the two groups was found for the SPPB score development over 3 years. Older adults with subjective memory complaints and in the lower quartile of omega-3 have a faster decline on gait speed compared to people in the three upper quartiles. Other longitudinal studies are needed to explore this association and to examine mechanisms.

Red blood cell membrane omega-3 fatty acid levels and physical performance: Cross-sectional data from the MAPT study

BACKGROUND & AIMS

Studies have shown that omega-3 polyunsaturated fatty acids (PUFAs) are associated with brain, cardiovascular and immune function, as well as physical performance and bone health in older adults. So far, few studies have highlighted the associations between PUFA status and performance-based tests of physical function. To study the associations between the omega-3 index (red blood cell (RBC) membrane content of omega-3 PUFAs, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) and physical performance measured with the Short Physical Performance Battery (SPPB) in a sample of community-dwelling older adults.

DESIGN

Cross-sectional study using the baseline data of the Multidomain Alzheimer's Disease Trial (MAPT), a randomized, placebo-controlled trial.

PARTICIPANTS AND MEASUREMENTS

1449 participants with available data on PUFAs were included. Omega-3 index and Short Physical Performance Battery (SPPB) scores were measured at enrollment and the omega-3 index expressed as the percentage of total fatty acid content was calculated. We also dichotomized the omega-3 index as low (lowest quartile) vs. high (three upper quartiles).

RESULTS

Participants were 75.2 (±4.4) years old, 64.5% were female. Bivariate analyses found that participants who were in the lowest omega-3 index quartile (Q1) had a SPPB score significantly lower than participants in the three other quartiles (Q2-Q4). However, adjusted (for age, gender, cognitive function, depressive status, Body Mass Index and grip strength) multiple linear regression showed that the omega-3 index-SPPB score association did not reach statistical significance [β = -0.166; (-0.346; 0.013); p = 0.07] in our sample.

CONCLUSION

This cross-sectional study found that participants with a low omega-3 index had worse performance-based test results of physical function than people with a high omega-3 index, but this association did not reach statistical significance once confounders were controlled for. Studies looking at the over-time associations between PUFA status and physical performance changes may shed more light on this topic.

Dietary interventions (plant sterols, stanols, omega-3 fatty acids, soy protein and dietary fibers) for familial hypercholesterolaemia

BACKGROUND

A cholesterol-lowering diet and several other dietary interventions have been suggested as a management approach either independently or as an adjuvant to drug therapy in children and adults with familial hypercholesterolaemia (FH). However, a consensus has yet to be reached on the most appropriate dietary treatment. Plant sterols are commonly used in FH although patients may know them by other names like phytosterols or stanols.

OBJECTIVES

To examine whether a cholesterol-lowering diet is more effective in reducing ischaemic heart disease and lowering cholesterol than no dietary intervention in children and adults with familial hypercholesterolaemia. Further, to compare the efficacy of supplementing a cholesterol-lowering diet with either omega-3 fatty acids, soya proteins, plant sterols or plant stanols.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Inborn Errors of Metabolism Trials Register, which is compiled from electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL) (updated with each new issue of The Cochrane Library), quarterly searches of MEDLINE and the prospective handsearching of one journal - Journal of Inherited Metabolic Disease. Most recent search of the Group's Inborn Errors of Metabolism Trials Register: 22 August 2013. We also searched PubMed to 05 February 2012.

SELECTION CRITERIA

Randomised controlled trials, both published and unpublished, where a cholesterol-lowering diet in children and adults with familial hypercholesterolaemia has been compared to other forms of dietary treatment or to no dietary intervention were included.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trial eligibility and risk of bias and one extracted the data, with independent verification of data extraction by a colleague.

MAIN RESULTS

In the 2014 update of the review, 15 trials have been included, with a total of 453 participants across seven comparison groups. The included trials had either a low or unclear risk of bias for most of the parameters used for risk assessment. Only short-term outcomes could be assessed due to the short duration of follow up in the included trials. None of the primary outcomes, (incidence of ischaemic heart disease, number of deaths and age at death) were evaluated in any of the included trials. No significant differences were noted for the majority of secondary outcomes for any of the planned comparisons. However, a significant difference was found for the following comparisons and outcomes: for the comparison between plant sterols and cholesterol-lowering diet (in favour of plant sterols), total cholesterol levels, mean difference 0.30 mmol/l (95% confidence interval 0.12 to 0.48); decreased serum LDL cholesterol, mean difference -0.60 mmol/l (95% CI -0.89 to -0.31). Fasting serum HDL cholesterol levels were elevated, mean difference -0.04 mmol/l (95% CI -0.11 to 0.03) and serum triglyceride concentration was reduced, mean difference -0.03 mmol/l (95% CI -0.15 to -0.09), although these changes were not statistically significant. Similarly, guar gum when given as an add on therapy to bezafibrate reduced total cholesterol and LDL levels as compared to bezafibrate alone.

AUTHORS' CONCLUSIONS

No conclusions can be made about the effectiveness of a cholesterol-lowering diet, or any of the other dietary interventions suggested for familial hypercholesterolaemia, for the primary outcomes: evidence and incidence of ischaemic heart disease, number of deaths and age at death,due to the lack of data on these. Large, parallel, randomised controlled trials are needed to investigate the effectiveness of a cholesterol-lowering diet and the addition of omega-3 fatty acids, plant sterols or stanols, soya protein, dietary fibers to a cholesterol-lowering diet.

Association of serum phospholipid PUFAs with cardiometabolic risk: beneficial effect of DHA on the suppression of vascular proliferation/inflammation

OBJECTIVES

Blood or dietary polyunsaturated fatty acids (PUFAs), particularly ω3-PUFAs were known for cardiovascular protective effect. However, the results are still controversial. We aimed to investigate the association of serum phospholipid PUFAs with cardiometabolic risk through cross-sectional/experimental studies.

DESIGN/METHODS

Serum phospholipid FA compositions and cardiometabolic risk parameters were measured in controls [healthy: n=987, metabolic syndrome (MetS): n=214] and CAD patients (CAD-only: n=152, CAD+MetS: n=56). Experimental assays were performed in vascular smooth muscle cells (VSMCs).

RESULTS

Major cardiometabolic risk markers, i.e. insulin resistance, hs-C-reactive proteins, and malondialdehyde were higher, and adiponectin and LDL particle size were lower in CAD patients, particularly those with MetS than in healthy controls. Serum linoleic acid (LA, C18:2ω-6) was lowest and dihomo-γ-linolenic acids (DGLAs, C20:3ω-6) were highest in CAD patients with MetS among the 4 groups. Docosahexaenoic acid (DHA, C22:6ω-3) was lower and arachidonic acid (AA, C20:4ω-6) and ω6/ω3-PUFAs were higher in CAD patients than in controls. ω3-PUFAs were significantly lower in CAD patients, particularly those with MetS than in healthy controls. Multiple regression analysis revealed that AA and DHA among serum FAs were mainly associated with the cardiometabolic risk (β'-coefficients for AA:0.336; DHA: -0.296) together with age, MetS factors, LA, DGLA and gender (r=0.529, p<0.001). Under LPS-induced stress condition, LA and DHA significantly suppressed VSMC proliferation. DHA also up-regulated the phosphorylation of p38 and ERK, and dramatically inhibited nuclear translocation of NF-κB-p65 in VSMCs.

CONCLUSION

AA and DHA were mainly associated with cardiometabolic risk. Particularly, DHA may be effective on suppression of vascular proliferation and inflammation.

Do fat supplements increase physical performance?

Fish oil and conjugated linoleic acid (CLA) belong to a popular class of food supplements known as "fat supplements", which are claimed to reduce muscle glycogen breakdown, reduce body mass, as well as reduce muscle damage and inflammatory responses. Sport athletes consume fish oil and CLA mainly to increase lean body mass and reduce body fat. Recent evidence indicates that this kind of supplementation may have other side-effects and a new role has been identified in steroidogenensis. Preliminary findings demonstrate that fish oil and CLA may induce a physiological increase in testosterone synthesis. The aim of this review is to describe the effects of fish oil and CLA on physical performance (endurance and resistance exercise), and highlight the new results on the effects on testosterone biosynthesis. In view of these new data, we can hypothesize that fat supplements may improve the anabolic effect of exercise.

Plasma phospholipid fatty acid composition in ischemic stroke: importance of docosahexaenoic acid in the risk for intracranial atherosclerotic stenosis

OBJECTIVE

While data on the relationship between fatty acid (FA) composition and the risk for total stroke have accumulated, the association between FA composition and the risk for intracranial atherosclerotic stenosis (ICAS) has never been studied. We compared plasma phospholipid FA composition between non-stroke control and ischemic stroke in Korean population, to discern the FA that distinguishes ICAS from total ischemic stroke patients.

METHODS

Non-stroke controls (n = 215) and stroke patients (no cerebral atherosclerotic stenosis, NCAS: n = 144 and ICAS: n = 104) were finally included in the analysis. Plasma phospholipid FA compositions were analyzed.

RESULTS

Age, coexistence of hypertension/diabetes were significantly different among the groups. Phospholipid FA compositions were significantly different between non-stroke control and ischemic stroke patients, and interestingly, between NCAS and ICAS in stroke patients. Pattern analysis showed that docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the ω3-polyunsaturated FAs were important FAs in distinguishing NCAS and ICAS in strokes. Particularly, the risk of ICAS was inversely associated with levels of DHA contents in phospholipids (OR: 0.590, 95% CI: 0.350-0.993, p < 0.05), indicating that the risk may be increased at lower levels of DHA contents.

CONCLUSION

DHA and EPA are important FAs for distinguishing NCAS and ICAS in strokes. Additionally, the risk of ICAS was inversely associated with the levels of phospholipid DHA, which indicates that sufficient amounts of DHA in plasma or in diet may reduce the risk of ICAS.

Low level of n-3 polyunsaturated fatty acids in erythrocytes is a risk factor for both acute ischemic and hemorrhagic stroke in Koreans

Evidence suggesting an association between n-3 polyunsaturated fatty acids (PUFA) and stroke risk has been inconsistent, possibly because previous studies have not differentiated between different stroke types. The present study investigated the hypothesis that tissue levels of n-3 PUFA are positively associated with hemorrhagic stroke and negatively associated with ischemic stroke. We recruited 120 subjects for this case-control study, with 40 cases each of hemorrhagic stroke, ischemic stroke, and unaffected controls. Patients with a family history of hemorrhagic stroke had a significantly increased risk for hemorrhagic stroke. Omega-3 Index (20:5n3 + 22:6n3 in erythrocytes) and 22:6n3 were negatively (P < .01) associated with the risk of both hemorrhagic and ischemic stroke in multivariate analyses. Saturated fatty acids 16:0 and 18:0 were positively associated, whereas 18:2n6 and 18:3n6 were negatively (P < .05) associated with risk of ischemic stroke. Monounsaturated fatty acid, 18:1n9, increased (P = .03) the odds of hemorrhagic stroke. Omega-3 Index and docosahexaenoic acid were significantly lower in patients with both subtypes of hemorrhagic stroke, subarachnoid and intracerebral hemorrhage, but only in one subtype of ischemic stroke, small-artery occlusion. Saturated fatty acids 16:0 and 18:0 were significantly higher, but 20:4n6 was significantly lower, in patients with small-artery occlusion. Linoleic acid was significantly lower in patients with small-artery occlusion and large-artery atherosclerosis, whereas 18:1n9 was higher in both subgroups of hemorrhagic stroke. In conclusion, the results of our case-control study suggest that erythrocyte n-3 PUFA may protect against hemorrhagic stroke and ischemic stroke, particularly in the case of small-artery occlusion.

Dietary treatment for familial hypercholesterolaemia

BACKGROUND

A cholesterol-lowering diet and several other dietary interventions have been suggested as a management approach either independently or as an adjuvant to drug therapy in children and adults with familial hypercholesterolemia. However, a consensus has yet to be reached on the most appropriate dietary treatment.

OBJECTIVES

To examine whether a cholesterol-lowering diet is more effective in reducing ischaemic heart disease and lowering cholesterol than no dietary intervention in children and adults with familial hypercholesterolaemia. Further, to compare the efficacy of supplementing a cholesterol-lowering diet with either omega-3 fatty acids, soya proteins, plant sterols or plant stanols.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Inborn Errors of Metabolism Trials Register.Most recent search of the Group's Inborn Errors of Metabolism Trials Register: 09 October 2009.We also searched PubMed till 01 June 2008.

SELECTION CRITERIA

Randomised controlled trials, both published and unpublished, where a cholesterol-lowering diet in children and adults with familial hypercholesterolaemia has been compared to other forms of dietary treatment or to no dietary intervention were included.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trial eligibility and methodological quality and one extracted the data, with independent verification of data extraction by a colleague.

MAIN RESULTS

In the present update, four new trials have been added making eleven trials with a total of 331 participants eligible for inclusion. Only short-term outcomes could be assessed due to the short duration of follow up in the included studies. None of the primary outcomes, (incidence of ischaemic heart disease, number of deaths and age at death) were evaluated in any of the included studies. No significant difference was noted for the majority of secondary outcomes for any of the planned comparisons. However, a significant difference was found only for the following comparison and outcome: total cholesterol levels for the comparison between plant sterols and cholesterol-lowering diet, mean difference 0.70 (95% confidence interval 0.19 to 1.21).

AUTHORS' CONCLUSIONS

No conclusions can be made about the effectiveness of a cholesterol-lowering diet, or any of the other dietary interventions suggested for familial hypercholesterolaemia, due to the lack of adequate data. Large, parallel, randomised controlled trials are needed to investigate the effectiveness of a cholesterol-lowering diet and the addition of omega-3 fatty acids, plant sterols or stanols, soya protein to a cholesterol-lowering diet.

Modification of blood antioxidant status and lipid profile in response to high-intensity endurance exercise after low doses of omega-3 polyunsaturated fatty acids supplementation in healthy volunteers

We investigated whether endurance exercise might modify the blood antioxidant status and lipid profile after omega-3 fatty acid supplementation. Two groups of healthy, fit males performed 1 h of exercise with a constant work load corresponding to 60% of their individual VO(2 max) and various pedaling rates (45 min-60 rev/min followed by a maximal rate), before and after receiving, over 6 weeks, omega-3 fatty acids in a daily dose of 1.3 g or placebo. The resting concentration of triglycerides decreased after omega-3 fatty acid consumption. In response to endurance exercise, the superoxide dismutase activity markedly decreased in sedentary control subjects. This effect was partially protected by omega-3 fatty acid consumption. Supplementation tended to increase atalase activity in response to exercise, and this activity was significantly higher after 1 h of recovery. We conclude that the beneficial effect of omega-3 fatty acid supplementation during endurance exercise may be due to the activation of the superoxide dismutase and catalase pathways.

The effect of supplementation with n-3 fatty acids on the physical performance in subjects with spinal cord injury

A global physical evaluation was performed in 21 males with spinal cord injury (SCI), at the beginning and at three and six months of omega-3 fatty acid (FA) supplementation. A significant increase in the proportion of eicosapentaenoic acid and docosahexanoic acid in plasma was observed in response to the supplementation (p<0.05). After six months of FA supplementation, strength endurance time increased from 127.7+/-19.0 s to 215.2+/-45.6 s in the right arm, and from 139+/-27.6 s to 237.7+/-48.7 s, in the left arm. The time to perform 20 repetitions of 70% maximum workload showed a reduction of 41% between the first and the third test. The time taken to cover a 90 meter long track, with a 6% slope, was reduced from 66.9+/-8.0 s to 59.3+/-6.7 s, at the end of the study (p<0.05). In conclusion, omega-3 FA supplementation could contribute to improve the functional capabilities in SCI subjects.

Non-invasive methods and stimuli for evaluating the skin's microcirculation

Vessels in the skin are arranged into superficial and deep horizontal plexuses and they are involved in thermoregulation, oxygen and nutritional support. The skin has a large number of functions and broad appeal spanning basic mechanistic and clinical research. Indeed, the skin can be used as a marker of normal and impaired vascular control and, owing to its accessibility and frequent involvement, is easy to investigate non-invasively. A large number of non-invasive methods are available for investigating the skin, ranging from those that permit the visualisation of microvessels, to those that monitor blood flow or one of its derivatives (e.g., skin temperature and transcutaneous oxygen). Such methods can be combined with non-invasive, dynamic stimuli (e.g., the use of cold or warm stimuli, activation of the peripheral nervous system or local neuronal systems, and the topical application of vasoactive drugs) and this potentially enables the differentiation of underlying disorders (e.g., primary from secondary Raynaud's phenomenon) and also to quantify changes over time or following intervention. The present article outlines the non-invasive methods and dynamic tests that can be used to investigate the microcirculation of the skin.

Fat supplementation, health, and endurance performance

Pre-exercise fat ingestion (i.e., long chain triacylglycerol ingestion 1 to 4 h before exercise), medium-chain triacylglycerols, fish oil, and conjugated linoleic acid have been suggested to alter metabolism to achieve weight loss, alter lipid profiles, or improve performance. However, studies have demonstrated that ingestion of meals with long-chain triacylglycerols before exercise has little or no effect on metabolism and does not alter subsequent exercise performance. Also, medium-chain triacylglycerol supplementation before or during exercise has not been shown to be ergogenic, although this could be related to the small amounts of medium-chain triacylglycerol that can be ingested before gastrointestinal discomfort occurs. Fish oil may improve red blood cell deformability, but these effects are likely to be small and do not seem to influence maximum oxygen delivery or exercise performance. Conjugated linoleic acid has been implicated in weight loss, but based on the results of human studies it must be concluded that the effects of conjugated linoleic acid on body weight loss are far less clear than those observed in animal studies. Most studies have not found any evidence for a beneficial effect of conjugated linoleic acid.

Consumption of fish and fish oils and decreased risk of stroke

Consumption of fish and fish oils was first associated with decreased risk of cardiovascular disease almost 50 years ago. Since then, a number of epidemiologic studies have evaluated whether their consumption is specifically associated with stroke. Ecologic/cross-sectional and case-control studies have generally shown an inverse association between consumption of fish and fish oils and stroke risk. Results from five prospective studies have been less consistent, with one showing no association, one showing a possible inverse association, and three demonstrating a significant inverse association. In the latest and largest of these, the Nurses Health Study, the relative risk of total stroke was lower, although not significantly so, among women who regularly ate fish than among those who did not. A significant decrease in the risk of thrombotic stroke (relative risk, 0.49; 95% confidence interval, 0.26-0.93) was observed among women who ate fish at least two times per week compared with women who ate fish less than once per month, after adjustment for age, smoking, and other cardiovascular risk factors; a nonsignificant decrease was observed among women in the highest quintile of long-chain omega-3 polyunsaturated fatty acid intake. No association was observed between consumption of fish or fish oil and hemorrhagic stroke. These data support the hypothesis that consumption of fish several times per week reduces the risk of thrombotic stroke but does not increase the risk of hemorrhagic stroke.

Blood pressure response to fish oil supplementation: metaregression analysis of randomized trials

OBJECTIVE

The antihypertensive effect of fish oil was estimated from randomized trials using metaregression analysis. Modification of the blood pressure (BP) effect by age, gender, blood pressure, and body mass index was examined.

METHODS

A total of 90 randomized trials of fish oil and BP were identified through MEDLINE (1966-March 2001). Trials with co-interventions, patient populations, non-placebo controls, or duration of < 2 weeks were excluded. A total of 36 trials (50 strata) were included, 22 of which had a double-blind design. Original reports were retrieved for data collection on sample size, study design, duration, fish oil dose, BP changes and baseline characteristics of trial populations. Pooled BP estimates were obtained by metaregression analysis, weighted for trial sample sizes. Stratified analyses according to population characteristics were performed.

RESULTS

Intake of fish oil was high in most trials (median dose: 3.7 g/day). Fish oil reduced systolic BP by 2.1 mmHg [95% confidence interval (CI): 1.0, 3.2; P < 0.01] and diastolic BP by 1.6 mmHg (95% CI: 1.0. 2.2; P < 0.01). Restricting the analysis to double-blind trials yielded BP reductions of 1.7 mmHg (95% CI: 0.3, 3.1) and 1.5 mmHg (95% CI: 0.6, 2.3), respectively. BP effects tended to be larger in populations that were older (> 45 years) and in hypertensive populations (BP >or= 140/90 mmHg).

CONCLUSIONS

High intake of fish oil may lower BP, especially in older and hypertensive subjects. The antihypertensive effect of lower doses of fish oil (< 0.5 g/day) however, remains to be established.

Moderate intake of n-3 fatty acids is associated with stable erythrocyte resistance to oxidative stress in hypertriglyceridemic subjects

BACKGROUND

The important triacylglycerol-lowering capacity of n-3 fatty acids is counterbalanced by their inherent sensitivity to oxidation. Inconsistent results about the latter have been reported in hypertriglyceridemic individuals. After incorporation into cell membranes, n-3 fatty acids may alter membrane-related functions. In view of the distinct composition of hypertriglyceridemic membranes and the prooxidant status in this condition, it can be surmised that cell enrichment with the oxidizable n-3 fatty acids will be associated with an increased hemolytic process.

OBJECTIVE

We sought to evaluate the effect of fish oil consumption on n-3 fatty acid incorporation into erythrocyte membranes and subsequent ex vivo oxidative-stress-induced hemolysis in normotriglyceridemic and hypertriglyceridemic subjects.

DESIGN

Sixteen normotriglyceridemic and 12 hypertriglyceridemic subjects were given 6 g fish oil/d for 8 wk. Blood samples were collected before and 4 and 8 wk after treatment. Resistance to 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced hemolysis was assayed in fresh erythrocyte suspensions, and erythrocyte samples were stored at -70 degrees C for later analysis of cholesterol, hemoglobin, fatty acids, vitamin E, and glutathione peroxidase activity.

RESULTS

Fish oil supplementation induced n-3 fatty acid incorporation in normotriglyceridemic and hypertriglyceridemic erythrocyte membranes without decreasing their resistance to AAPH. n-3 Fatty acids significantly protected normotriglyceridemic but not hypertriglyceridemic erythrocytes against hemolysis. In normotriglyceridemic subjects only, the higher resistance to hemolysis correlated with changes in cell vitamin E.

CONCLUSION

Although they exhibit a high susceptibility to oxidation, n-3 fatty acids may preserve membrane integrity and represent an added benefit in the treatment of hypertriglyceridemic patients.

Dietary treatment for familial hypercholesterolaemia

BACKGROUND

Familial hypercholesterolaemia is an inherited disorder characterised by a raised blood cholesterol, the presence of xanthomatosis and premature ischaemic heart disease. The aim of treatment is the reduction of blood LDL cholesterol concentrations in order to reduce the risk of ischaemic heart disease. Current treatment is based on a cholesterol lowering diet alone or in combination with drug therapy. Many of the drugs found to be effective in treating adults with this disease are not licensed for use in children, therefore diet is the main treatment of children with familial hypercholesterolaemia. In addition to the cholesterol-lowering diet, several other dietary interventions have been suggested and consensus has yet to be reached on the most appropriate dietary treatment for children and adults with familial hypercholesterolaemia.

OBJECTIVES

To examine the evidence that in children and adults with familial hypercholesterolaemia, a cholesterol lowering diet is more effective at lowering cholesterol and reducing incidence of ischaemic heart disease than no intervention or than other dietary interventions.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Trials Register, a specialist trials register which comprises references identified from comprehensive electronic database searches, handsearching relevant journals and handsearching abstract books of conference proceedings. Additional studies were identified from handsearching the Journal of Inherited Metabolic Disease (from inception, 1978 to 2000) and from the reference lists of identified studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs), both published and unpublished, where a cholesterol lowering diet in children and adults with familial hypercholesterolaemia has been compared to other forms of dietary treatment or to no dietary intervention. Trials which include patients with familial hypercholesterolaemia alongside patients with non-familial hypercholesterolaemia were only included if the group of familial patients was well defined and the results for these patients were available.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the trial eligibility and methodological quality and one reviewer extracted the data, with independent verification of data extraction by a colleague.

MAIN RESULTS

Only short term outcomes could be assessed in this review due to the length of the five eligible studies. Compliance to treatment, quality of life, mortality and evidence of ischaemic or atheromatous disease were not assessed in the studies identified. No differences were found between the cholesterol-lowering diet and all other diets for all of the short term outcomes assessed.

REVIEWER'S CONCLUSIONS

No conclusions can be made about the effectiveness of the cholesterol-lowering diet, or any of the other dietary interventions suggested for familial hypercholesterolaemia, due to the lack of adequate data. A large, parallel, randomised controlled trial is needed to investigate the effectiveness of the cholesterol-lowering diet and other dietary interventions for FH. It is also possible that data from trials including subjects with both familial and non-familial hypercholesterolaemia could alter the results of future updates of this review and until further evidence is available current dietary treatment of FH should continue to be observed and monitored with care.

Update on solid-phase extraction for the analysis of lipid classes and related compounds

This article provides information on the different procedures and methodologies developed when solid-phase extraction (SPE) is used for lipid component separation. The analytical systematics, established by different authors and designed to separate groups of compounds and also specific components by using a combination of chromatographic supports and solvents are presented. The review has been divided into three parts, which we consider well defined: edible fats and oils, fatty foods and biological samples. Separations of non-polar and polar lipids is the most extensive systematic, although many other published methods have been established to isolate specific components or a reduced number of components from edible fats and oils, fatty foods or biological samples susceptible to further analysis by other quantitative techniques.

Effects of exercise and n-3 fatty acids on postprandial lipemia

Because n-3 fatty acid ingestion and aerobic exercise each has been associated with diminished postprandial lipemia (PPL), the purpose of this study was to evaluate the effect of a combination of these two factors on PPL. Sedentary men underwent a standard dietary preparation, including a 12-h fast before each trial. Six subjects performed a control trial (fat meal, 100 g fat) and an n-3 fatty acid trial (fat meal after 3 wk of n-3 fatty acid supplementation at 4 g/day). In a parallel experiment, six different subjects underwent a control trial and n-3 fatty acid supplementation + 60 min of exercise before ingestion of the fat meal. Supplementation with n-3 fatty acid significantly decreased baseline triglyceride (TG) concentrations but did not significantly affect PPL. The combination of n-3 fatty acid and exercise had no effect on the postprandial TG response. The present study suggests that n-3 fatty acid supplementation lowers resting TG concentrations but inhibits the beneficial effect of aerobic exercise on the postprandial TG response.

Effect of long-chain n-3 polyunsaturated fatty acids on fasting and postprandial triacylglycerol metabolism

Elevated plasma triacylglycerol concentrations have been associated with increased risk of coronary heart disease (CHD). In the past, the epidemiologic evidence about the causal role of triacylglycerols in CHD has not been well regarded, but recent prospective evidence shows that nonfasting plasma triacylglycerol concentration is a strong and independent predictor of future myocardial infarction. Elevated plasma triacylglycerol concentrations are associated with other CHD risk factors, namely reduced HDL-cholesterol concentrations and a preponderance of highly atherogenic, small, dense LDL particles. Plasma triacylglycerol concentrations increase after the ingestion of a fat-containing meal, and elevated postprandial triacylglycerolemia leads to a series of metabolic reactions that reduce HDL-cholesterol concentrations and promote the formation of small, dense LDL particles. The magnitude of the postprandial response is largely determined by fasting plasma triacylglycerol concentrations. Metabolism of plasma triacylglycerols also influences postprandial factor VII activation and the postprandial lipemic responsiveness to dietary cholesterol. Therefore, dietary factors that improve fasting plasma triacylglycerol concentrations must have a role in a healthy diet. Eicosapentaenoic and docosahexaenoic acids are n-3 polyunsaturated fatty acids (PUFAs) in fish oil that effectively reduce plasma triacylglycerol concentrations. Because n-3 PUFAs are effective at low doses (1 g n-3 PUFA/d), they provide a realistic option for the optimization of plasma triacylglycerol metabolism.

Exercise performance, red blood cell deformability, and lipid peroxidation: effects of fish oil and vitamin E

Previous studies have indicated that fish oil supplementation increases red blood cell (RBC) deformability, which may improve exercise performance. Exercise alone, or in combination with an increase in fatty acid unsaturation, however, may enhance lipid peroxidation. Effects of a bicycle time trial of approximately 1 h on RBC characteristics and lipid peroxidation were, therefore, studied in 24 trained cyclists. After 3 wk of fish oil supplementation (6 g/day), without or with vitamin E (300 IU/day), trial performance, RBC characteristics, and lipid peroxidation were measured again. RBC deformability appeared to decrease during endurance exercise. After correction for hemoconcentration, plasma total tocopherol concentrations decreased by 0.77 micromol/l (P = 0. 012) or 2.9% and carotenoid concentrations by 0.08 micromol/l (P = 0. 0008) or 4.5%. Endurance exercise did not affect the lag time and rate of in vitro oxidation of low-density lipoproteins (LDLs), but the maximum amount of conjugated dienes formed decreased by 2.1 +/- 1.0 micromol/mmol LDL cholesterol (P = 0.042) or 1.2%. Fish oil supplementation with and without vitamin E did not affect RBC characteristics or exercise performance. Both supplements decreased the rate of LDL oxidation, and fish oil supplementation with vitamin E delayed oxidation. The amount of dienes, however, was not affected. The supplements also did not change effects of exercise. We conclude that the changes observed during endurance exercise may indicate increased oxidative stress, but further research is necessary to confirm this. Fish oil supplementation does not improve endurance performance, but it also does not cause or augment changes in antioxidant levels or LDL oxidation during exercise.

Incorporation of n-3 fatty acids into plasma lipid fractions, and erythrocyte membranes and platelets during dietary supplementation with fish, fish oil, and docosahexaenoic acid-rich oil among healthy young men

The effects of n-3 fatty acid supplementation in the form of fresh fish, fish oil, and docosahexaenoic acid (DHA) oil on the fatty acid composition of plasma lipid fractions, and platelets and erythrocyte membranes of young healthy male students were examined. Altogether 59 subjects (aged 19-32 yr, body mass index 16.8-31.3 kg/m2) were randomized into the following diet groups: (i) control group; (ii) fish diet group eating fish meals five times per week [0.38 +/- 0.04 g elcosapentaenoic acid (EPA) and 0.67 +/- 0.09 g DHA per day]; (iii) DHA oil group taking algae-derived DHA oil capsules (1.68 g/d DHA in triglyceride form); and (iv) fish oil group (1.33 g EPA and 0.95 g DHA/d as free fatty acids) for 14 wk. The fatty acid composition of plasma lipids, platelets, and erythrocyte membranes was analyzed by gas chromatography. The subjects kept 4-d food records four times during the study to estimate the intake of nutrients. In the fish diet, in DHA oil, and in fish oil groups, the amounts of n-3 fatty acids increased and those of n-6 fatty acids decreased significantly in plasma lipid fractions and in platelets and erythrocyte membranes. A positive relationship was shown between the total n-3 polyunsaturated fatty acids (PUFA) and EPA and DHA intake and the increase in total n-3 PUFA and EPA and DHA in all lipid fractions analyzed. DHA was preferentially incorporated into phospholipid (PL) and triglyceride (TG) and there was very little uptake in cholesterol ester (CE), while EPA was preferentially incorporated into PL. and CE. The proportion of EPA in plasma lipids and platelets and erythrocyte membranes increased also by DHA supplementation, and the proportion of linoleic acid increased in platelets and erythrocyte membranes in the DHA oil group as well. These results suggest retroconversion of DHA to EPA and that DHA also interferes with linoleic acid metabolism.

Lack of renal effects of fish oil administration in patients with advanced cirrhosis and impaired glomerular filtration

The treatment of renal failure in cirrhotic patients with ascites remains unsatisfactory. Recent studies have shown that the dietary supplementation with fish oil improves the renal function of normal subjects, as well as that of patients with renal failure of different etiologies. We have investigated the renal effects of a daily supplementation for 1 month of 12 g fish oil (27% C20:5 n-3 eicosapentanoic acid [EPA], and 23% C22:6 n-3 docosahexanoic acid [DHA]) in a prospective study of cirrhotic patients with ascites, nine with normal renal function (group 1) and eight with renal failure (glomerular filtration rate [GFR] < 60 mL/min, group 2). Compliance with the dietary regimen was confirmed by fatty acid chromatography that showed increased plasma concentration of EPA (from 1.5 +/- 0.7% to 3.7 +/- 0.8%, P = .024, in group 1; and from 0.53 +/- 0.3% to 2.9 +/- 0.8%, P = .03, in group 2) and of DHA (from 2.1 +/- 0.4% to 3.4 +/- 0.3%, P = .008, in group 1; and from 1.45 +/- 0.5% to 3.8 +/- 0.4%, P = .05, in group 2). At the end of the study, in patients from group 1, the glomerular filtration rate increased by 19% (from 94 +/- 8 to 113 +/- 13 mL/min, P = .039), and the urine flow increased by 39% (from 0.85 +/- 0.14 to 1.12 +/- 0.2 mL/min, P = .039), while no changes occurred in the renal function of patients from group 2. No changes were observed in the urinary excretion of prostaglandin (PG) E2 or of 6-keto prostaglandin-1-alpha (6-K-PGF1-alpha) nor in plasma renin activity (PRA) or the plasma concentration of aldosterone (PA) or antidiuretic hormone (ADH) in both groups. As far as undesirable effects of fish oils were considered, the mean arterial pressure (MAP) decreased in both groups (group 1: from 88.6 +/- 2 to 85.3 +/- 2 mm Hg, P = .015; group 2: from 88.2 +/- 3 to 82.8 +/- 3 mm Hg, P = .05), and bleeding time displayed a significant increase when patients were considered collectively (from 744 +/- 89 to 872 +/- 106 seconds, P = .0068). In conclusion, the administration of fish oil for 1 month was unable to improve renal function in cirrhotic patients with ascites and renal failure. The occurrence of undesirable effects, such as the reduction of arterial pressure and the prolongation of bleeding time, argues against the use of fish oils in these patients.

Microcirculation, vitamin E and omega 3 fatty acids: an overview

We have observed significant increases in LDF and similar trends for CBV after FO supplementation in younger subjects (both normolipidemic and hyperlipidemic). In elderly subjects, this trend appears to be reversed unless subjects are supplemented with higher doses of vit. E (100 IU/10 KG/day). Our mouse data suggest that dietary vit. E at 100 IU/Kg does not adequately protect against lipid oxidation in vivo or in vitro following an oxidative insult when mice are fed an 8% FO & 2% linoleic acid containing diet. It has been reported that FO significantly lowers triglycerides and VLDL-cholesterol (especially where subjects have higher initial triglyceride values) and tends to increase LDL-cholesterol and Apo-B100. These findings are all the more important because the oxidation of LDL from FO-supplemented subjects caused a time-dependent increase in the ability to facilitate albumin transfer which was not diminished following a 2 month washout (WO). Addition of vit. E to the FO supplement prevented this change. These data suggest that FO supplementation without sufficient vit. E may be deleterious to the vascular endothelium. The western fat blend supplement appeared to be protective with increased length of supplementation most likely due to increased MONO fatty acids which are resistant to oxidation; vit. E supplementation appeared to have little additional effect. Our combined studies, and those reported by others, suggest that in humans, increased peripheral microcirculatory flow is most likely due to changes in precapillary vascular tone i.e., vasodilation. It is also possible that subtle changes in each of the three variables i.e. blood pressure, blood viscosity and vascular tone when combined may contribute to the significant changes which we have noted as increased LDF or CBV after intervention with dietary n-3 fatty acids. We hypothesize that interactions between dietary fatty acids and vit. E alters the ratios of vasoconstrictive-platelet aggegatory/vasodilatory-antiplatelet aggregatory agents (TXA2 and endothelin/PGI2 and nitric oxide), the expression of adhesion molecules (P-selectin and E-selectin) and thereby directly influences the modulation of free radical mediated events between blood elements and the vascular endothelium. Fatty acids of the n3 series may alter these events by favoring the production of vasodilatory compounds and decreased expression of P and/or E-selectins, provided that these highly oxidizable lipids are protected by adequate antioxidants.

n-3 fatty acids and lipoproteins: comparison of results from human and animal studies

The impact of n-3 fatty acids (FA) on blood lipoprotein levels has been examined in many studies over the last 15 yr in both animals and humans. Studies in humans first demonstrated the potent triglyceride-lowering effect of n-3 FA, and these were followed up with animal studies to unravel the mechanism of action. This paper reviews the reported effects of n-3 FA on blood lipoproteins in 72 placebo-controlled human trials, at least 2 wk in length and providing 7 or less g of n-3 FA/day. Trials in normolipidemic subjects (triglycerides < 2.0 mM; 177 mg/dL) were compared to those in hypertriglyceridemic patients (triglycerides > or = 2.0 mM). In the healthy subjects, mean triglyceride levels decreased by 25% (P < 0.0001), and total cholesterol (C) levels increased by 2% (P < 0.009) due to the combined increases in low density lipoprotein (LDL)-C (4%, P < 0.02) and high density lipoprotein (HDL)-C (3%, P < 0.008). In the patients, triglyceride levels decreased by 28% (P < 0.0001), LDL-C rose by 7% (P < 0.0001), but neither total C nor HDL-C changed significantly. Although the effect on triglyceride levels is also observed in rats and swine, it is rarely seen in mice, rabbits, monkeys, dogs, and hamsters. Whereas n-3 FA have only a minor impact on lipoprotein C levels in humans, they often markedly lower both total C and HDL-C levels in animals, especially monkeys. These differences are not widely appreciated and must be taken into account when studying the effects of n-3 FA on lipoprotein metabolism.

Blood pressure-lowering effect of fish oil is independent of thromboxane A2 level in spontaneously hypertensive rats

Whether the alterations in the synthesis of thromboxane A2 (TXA2) is the direct mechanism underlying the blood pressure-lowering effect of fish oil was investigated in this study. Six groups of 11 male spontaneously hypertensive rats were fed semipurified diets containing corn or fish oils and graded levels (50, 5000 or 15,000 ppm) of dietary vitamin E for 8 weeks. Plasma TXA2, assayed by RIA, was significantly greater in the corn oil group than in the fish oil group (P < 0.05). Compared to 50 ppm dietary vitamin E, 5000 and 15 000 ppm dietary vitamin E, respectively, significantly decreased plasma TXA2 (P < 0.05). Systolic, mean or diastolic blood pressure, evaluated by the tail cuff method, were significantly higher in the corn oil group than in the fish oil group (P < 0.05). However, vitamin E had no effect on blood pressure. No relationship between TXA2 and blood pressure was found. Experimental results indicated that the alterations in the synthesis of TXA2 were not the direct antihypertensive effect of fish oil.

Dietary fatty acids, membrane transport, and oxidative sensitivity in human erythrocytes

This study examined effects of dietary n-3 fatty acids on age-related changes in erythrocyte anion transport and susceptibility to oxidation. Blood was drawn from healthy adult volunteers before and after six weeks' supplementation (nine/group) with 4.0 g/day of safflower oil (containing 2.9 g n-6 fatty acids) or fish oil (containing 1.2 g long-chain n-3 fatty acids). Following density separation of young and old erythrocytes, membrane anion transport and cell membrane lipid composition were measured. Oxidative damage was measured in erythrocyte ghosts exposed to a free radical generator. Fish oil significantly increased 16:0 and 20:5n-3 in ghosts of both young and old cells, and 22:5n-3 and 22:6n-3 in old cells alone. Safflower oil increased 16:0, 18:0, 18:1n-9, and 22:5n-6 in ghosts of young cells only. The age-dependent increase in membrane anion transport (P < 0.01) was decreased by dietary fish oil supplementation, but not by safflower oil supplementation. Safflower oil and fish oil increased the susceptibility of both young and old erythrocytes to oxidative damage by free radical generation (P < 0.001).

Does fish oil lower blood pressure? A meta-analysis of controlled trials

BACKGROUND

In a meta-analysis of 31 placebo-controlled trials on 1356 subjects, we examined the effect of omega-3 fatty acids in fish oil on blood pressure by grouping studies that were similar in fish oil dose, length of treatment, health of the subjects, or study design.

METHODS AND RESULTS

The mean reduction in blood pressure caused by fish oil for the 31 studies was -3.0/-1.5 mm Hg (95% confidence intervals: systolic blood pressure: -4.5, -1.5; diastolic blood pressure: -2.2, -0.8). There was a statistically significant dose-response effect when studies were grouped by omega-3 fatty acid dose: -1.3/-0.7 mm Hg at doses < or = 3 g/d, -2.9/-1.6 mm Hg at 3.3 to 7 g/d, and -8.1/-5.8 mm Hg at 15 g/d. Both eicosapentaenoic acid and docosahexaenoic acid were significantly related to blood pressure response. There was no effect on blood pressure in eight studies of "healthy" persons (mean reduction, -0.4/-0.7 mm Hg) at an overall mean dose of 4.2 g omega-3 fatty acids/d. By contrast, there was a significant effect of -3.4/-2.0 mm Hg in the group of hypertensive studies with a mean fish oil dose of 5.6 g/d and on systolic blood pressure only in six studies of hypercholesterolemic patients (-4.4/-1.1 mm Hg) with a mean dose of 4.0 g/d. A nonsignificant decrease in blood pressure was observed in four studies of patients with atherosclerotic cardiovascular disease (-6.3/-2.9 mm Hg). Variations in the length of treatment (from 3 to 24 weeks), type of placebo, and study design (crossover or parallel groups) did not appear to account for inconsistent findings among studies.

CONCLUSIONS

There is a dose-response effect of fish oil on blood pressure of -0.66/-0.35 mm Hg/g omega-3 fatty acids. The hypotensive effect may be strongest in hypertensive subjects and those with clinical atherosclerotic disease or hypercholesterolemia.

Effects of dietary fatty-acid supplementation on fatty-acid composition and deformability of young and old erythrocytes

The effects of cell age on erythrocyte phospholipid fatty-acid composition and deformability were examined in 20 healthy adults (11 male, 9 female) prior to and following 12 weeks of dietary supplementation with 3.5 g/day of safflower oil (high in n - 6 fatty acids) or fish oil (high in n - 3 fatty acids). In the absence of dietary supplementation, old erythrocytes demonstrated an increase in filtration time (P < 0.001), an increase in membrane phospholipid total n - 6 fatty acids (P < 0.01), and a decrease in total n - 3/total n - 6 ratio (P < 0.01) compared to young erythrocytes. Both safflower and fish oil supplementation attenuated age-related differences in membrane phospholipid total n - 6 and total n - 3 fatty acids. Fish oil supplementation also increased the proportion of n - 3 fatty acids (P < 0.01) and the n - 3/n - 6 ratio (P < 0.05) in the phospholipids of both young and old erythrocytes, and eliminated age-related differences in erythrocyte filtration time by reducing the relative filtration time of the old erythrocytes.

High dose eicosapentaenoic acid ethyl ester: effects on lipids and neutrophil leukotriene production in normal volunteers

1. A 93% pure ethyl ester of eicosapentaenoic acid was investigated for tolerability and biochemical effects on neutrophil leukotriene synthesis and plasma lipoproteins when given in high dose. Six healthy volunteers received 6 g eicosapentaenoic acid ethyl ester daily for 6 weeks, followed by a 4 week wash-out and then 18 g daily for 6 weeks. 2. There was inhibition of neutrophil leukotriene B4 and 5-hydroxyeicosatetraenoic acid synthesis, with no significant differences between low and high dose. 3. There was a dose dependent increase in leukotriene B5 and 5-hydroxyeicosatetraenoic acid acid synthesis. 4. Plasma triglycerides were reduced maximally on 6 g daily, with no greater suppression at 18 g daily. 5. Plasma cholesterol was only suppressed significantly at 18 g daily. 6. The 6 g daily dose was well tolerated but the 18 g daily dose produced diarrhoea and steatorrhoea.

Effect of fish oil on atherogenesis in Watanabe heritable hyperlipidemic rabbit

The effect of dietary supplementation with fish oil was investigated in the Watanabe heritable hyperlipidemic (WHHL) rabbit. Rabbits were fed Maxepa (1 g/kg body weight) from weaning for a 6-month period and were compared to controls. Fish oil supplements resulted in significant decreases in plasma triglyceride and cholesterol at 4 weeks after the start of the study, and these differences persisted over the 6-month period. No differences in the distribution of cholesterol or triglyceride among lipoprotein particles were found, nor were there differences in low density lipoprotein particle size. The decreases in plasma cholesterol and triglyceride were accompanied by significant increases in the percent of eicosapentaenoic and docosahexaenoic acids in both plasma and platelets. Fish oil supplementation resulted in a decrease in platelet count and response to the aggregating agents adenosine diphosphate, arachidonic acid, and collagen. Systolic blood pressure was significantly lower in the rabbits fed fish oil. At the end of the study period, aortic free and esterified cholesterol and intimal surface area covered with plaque were determined in the arch and in the descending and abdominal aorta. Significantly less cholesterol was found in the descending and abdominal aorta. These differences were mirrored by decreased activities of acid lipase and N-acetyl-beta-glucosaminidase. In contrast, no differences in the intimal surface area covered with plaque were found. In conclusion, dietary fish oil resulted in a decrease in aortic lipid deposition in the WHHL rabbit, which may have been due to decreases in plasma triglyceride and cholesterol, platelet count and aggregability, and systolic blood pressure.

The combined effects of N-3 fatty acids and aspirin on hemostatic parameters in man

Both fish oils and aspirin are readily available to the consumer as over-the-counter preparations. Since both of these products have been shown to prolong bleeding times, it is possible that hemostasis might be adversely affected in subjects taking them in combination. This study was undertaken to examine the effects of n-3 fatty acids and aspirin on platelet function. Eight healthy men took a total of 485 mg of aspirin over 3 days before beginning two weeks of fish oil supplementation (4.5 g of n-3 fatty acids/day). Subjects continued with fish oil while resuming aspirin treatment for 3 days. Aspirin alone prolonged bleeding times by 34% (p less than 0.05). Fish oil alone raised bleeding times only slightly (9%; N.S.), but aspirin plus fish oil raised them by 78% (p less than 0.01). The increase in bleeding times with the combination (78%) was not significantly different than the sum of the individual increases (43%). The effects of fish oil and aspirin on platelet aggregation were investigated using single and dual agonists. Although fish oil alone did not significantly raise aggregation thresholds for collagen, arachidonic acid, or PAF, it did reduce the extent of aggregation with collagen. When challenged by single or dual agonists, the combination of fish oil and aspirin did not make platelets less sensitive than did aspirin alone. Since fish oil and aspirin had synergistic effects on bleeding times, but not on platelet aggregation, these two substances appear to affect hemostasis by different mechanisms.

Dietary supplementation with n-3 polyunsaturated fatty acids and human platelet function: a review with particular emphasis on implications for cardiovascular disease

The low incidence of myocardial infarction in Greenland Eskimos may be due to their intake of marine food with a high content of n-3 polyunsaturated fatty acids (PUFAs). In Eskimos the platelet count is lowered, the platelet aggregation is inhibited, the bleeding time is prolonged and the ratio between proaggregatory thromboxanes and anti-aggregatory prostacyclins is decreased, when compared to age- and sex-matched Danes. In this review, studies evaluating the effect of a fish diet or fish-oil supplementation on human platelet function are summarized. Most studies have demonstrated that supplementation with n-3 PUFAs can cause inhibition of platelet behaviour. The optimal dose of n-3 PUFAs and the patient groups most likely to profit from supplementation need to be defined. The safety and the clinical effect of the supplementation should be investigated in long-term studies.

The effects of omega-3 polyunsaturated fatty acids on blood pressure: a methodologic analysis of the evidence

The potentially beneficial blood pressure (BP)-lowering effects of marine omega-3 polyunsaturated fatty acids (omega-3-PUFAs) remain controversial. The objective of this qualitative and quantitative (meta-analysis) analysis was to evaluate the results of all available randomized controlled trials that studied the effect of omega-3-PUFAs on BP response. A comprehensive search of the English literature from 1970 to 1988 disclosed only six randomized controlled investigations out of 22 published reports. Four of these were evaluable and therefore eligible for this analysis. Of these, only one evaluated hypertensive subjects. In two trials, there were statistically significant reductions in BP; the one reporting an investigation of hypertensive subjects showed the greatest reduction. Using established methodologic criteria, the quality of each report was evaluated by independent observers. Following this appraisal, the outcomes of each investigation were reanalyzed and pooled using a meta-analysis. There was no statistically significant difference between the omega-3-PUFA groups and the control groups, possibly because of failure to include hypertensive subjects in all but one trial. Despite the positive effects in two studies, little scientifically valid evidence is available to demonstrate a significant BP-lowering effect of omega-3-PUFAs. Areas needing more attention in future research are identified and methods to improve study designs are suggested.

Absorption and transport of fat in mammals with emphasis on n-3 polyunsaturated fatty acids

The current state of knowledge concerning the absorption and transport of dietary fat with emphasis on long-chain polyunsaturated n-3 fatty acids in mammals is reviewed. It is apparent that long-chain polyunsaturated n-3 fatty acids, either as free acids or as part of triglycerides, are readily absorbed in the gut and transported by the circulatory system. Indeed, it would appear that long-chain polyunsaturated n-3 fatty acids are digested, absorbed and transported similarly to other long-chain fatty acids with only minor variations, although there is much that is still not understood about these processes. The main unresolved issues in the area of the absorption and transport of long-chain polyunsaturated n-3 fatty acids appear to be: 1) If they, when located in the 2-position of triglycerides, have unique metabolic pathways; and 2) whether the unnatural forms, i.e., methyl or ethyl ester derivatives, are suitable vehicles for administration as dietary supplements. The effect in man of dietary, long-chain polyunsaturated n-3 fatty acids on blood serum lipid and lipoprotein levels, particularly the low density lipoproteins, remains controversial, except for the well-documented reduction in serum triglyceride levels. Also, there is uncertainty regarding their distribution and metabolism in tissues. Finally, if the consumption of long-chain polyunsaturated n-3 fatty acids has beneficial health consequences, what is the appropriate therapeutic dose? In view of these important, unresolved issues and uncertainties, it would seem prudent to direct additional research toward a better understanding of the overall process by which fat is digested, absorbed and transported.