Fish consumption and risk of stroke and its subtypes: accumulative evidence from a meta-analysis of prospective cohort studies

Marine OMEGA-3 fatty acids in the prevention of cardiovascular disease

Omega-6 (ω6) and omega-3 (ω3) fatty acids are two classes of dietary polyunsaturated fatty acids derived from linoleic acid (18:2ω6) and α-linolenic acid (18:3ω3), respectively. Enzymatic metabolism of linoleic and α-linolenic acids generates arachidonic acid (20:4ω6) and eicosapentaenoic acid (20:5ω3; EPA), respectively, both of which are substrates for enzymes that yield eicosanoids with multiple and varying physiological functions. Further elongation and desaturation of EPA yields the 22-carbon fatty acid docosahexaenoic acid (22:6ω3; DHA). The main dietary source of EPA and DHA for human consumption is fish, especially oily fish. There is considerable evidence that EPA and DHA are protective against cardiovascular disease (heart disease and stroke), particularly in individuals with pre-existing disease. ω3 Fatty acids benefit multiple risk factors including blood pressure, blood vessel function, heart function and blood lipids, and they have antithrombotic, anti-inflammatory and anti-oxidative actions. ω3 Fatty acids do not adversely interact with medications. Supplementation with ω3 fatty acids is recommended in individuals with elevated blood triglyceride levels and patients with coronary heart disease. A practical recommendation for the general population is to increase ω3 fatty acid intake by incorporating fish as part of a healthy diet that includes increased fruits and vegetables, and moderation of salt intake. Health authorities recommend the general population should consume at least two oily fish meals per week.

Docosahexaenoic acid regulates vascular endothelial cell function and prevents cardiovascular disease

Docosahexaenoic acid (DHA) is present in high concentrations in salmon, herring, and trout. Epidemiologic studies have shown that high dietary consumption of these and other oily fish is associated with reduced rates of myocardial infarction, atherosclerosis, and other ischemic pathologies. Atherosclerosis is induced by inflammation and can lead to acute cardiovascular events and extensive plaque. DHA inhibits the development of inflammation in endothelial cells, alters the function and regulation of vascular biomarkers, and reduces cardiovascular risk. It also affects vascular relaxation and constriction by controlling nitric oxide and endothelin 1 production in endothelial cells. DHA also contributes to the prevention of arteriosclerosis by regulating the expression of oxidized low density lipoprotein receptor 1, plasminogen activator inhibitor 1, thromboxane A2 receptor, and adhesion molecules such as vascular cell adhesion molecule-1, monocyte chemoattractant protein-1, and intercellular adhesion molecule 1 in endothelial cells. Recent research showed that DHA reduces the increase in adhesion factor expression induced by lipopolysaccharide by suppressing toll-like receptor 4. A new mechanism of action of DHA has been described that is mediated through endothelial free fatty acid receptor 4, associated with heme oxygenase 1 induction by Nrf2. However, the efficacy and mechanisms of action of DHA in cardiovascular disease prevention are not yet completely understood. The aim of this paper was to review the effects of DHA on vascular endothelial cells and recent findings on their potential for the prevention of circulatory diseases.

Omega-3 polyunsaturated fatty acids for cardiovascular diseases: present, past and future

INTRODUCTION

Large-scale epidemiological studies on Greenlandic, Canadian and Alaskan Eskimos have examined the health benefits of omega-3 fatty acids consumed as part of the diet, and found statistically significant relative reduction in cardiovascular risk in people consuming omega-3 fatty acids. Areas covered: This article reviews studies on omega-3 fatty acids during the last 50 years, and identifies issues relevant to future studies on cardiovascular (CV) risk. Expert commentary: Although a meta-analysis of large-scale prospective cohort studies and randomized studies reported that fish and fish oil consumption reduced coronary heart disease-related mortality and sudden cardiac death, omega-3 fatty acids have not yet been shown to be effective in secondary prevention trials on patients with multiple cardiovascular disease (CVD) risk factors. The ongoing long-term CV interventional outcome studies investigate high-dose, prescription-strength omega-3 fatty acids. The results are expected to clarify the potential role of omega-3 fatty acids in reducing CV risk. The anti-inflammatory properties of omega-3 fatty acids are also important. Future clinical trials should also focus on the role of these anti-inflammatory mediators in human arteriosclerotic diseases as well as inflammatory diseases.

The potential impact of compositional changes in farmed fish on its health-giving properties: is it time to reconsider current dietary recommendations?

Assessment of national dietary guidelines in a number of European countries reveals that some are based on cohort studies, focusing on total seafood consumption, while others are based on the content of EPA and DHA, distinguishing between oily and other fish. The mean actual intake of fish in most countries is around or below the recommended intake, with differences in intake of fish being present between sex and age groups. Many people do not reach the national recommendation for total fish intake. Dietary recommendations for fish and EPA/DHA are based mainly on data collected more than 10 years ago. However, methods of farmed fish production have changed considerably since then. The actual content of EPA and DHA in farmed salmon has nearly halved as the traditional finite marine ingredients fish meal and fish oil in salmon diets have been replaced with sustainable alternatives of terrestrial origin. As farmed salmon is an important source of EPA and DHA in many Western countries, our intake of these fatty acids is likely to have decreased. In addition, levels of vitamin D and Se are also found to have declined in farmed fish in the past decade. Significant changes in the EPA and DHA, vitamin D and Se content of farmed fish means that average intakes of these nutrients in Western populations are probably lower than before. This may have consequences for the health-giving properties of fish as well as future dietary recommendations for fish intake.

Fish consumption in relation to myocardial infarction, stroke and mortality among women and men with type 2 diabetes: A prospective cohort study

BACKGROUND & AIMS

The accumulated evidence supports an inverse association of fish consumption with cardiovascular disease and mortality, but data among patients with type 2 diabetes are sparse. We aimed to assess fish consumption in relation to myocardial infarction (MI), stroke and mortality among individuals with type 2 diabetes.

METHODS

Women and men with diagnosed type 2 diabetes (n = 2225; aged 45-84 years) within two population-based cohorts (the Swedish Mammography Cohort and the Cohort of Swedish Men) were followed from 1998 through 2012. Cox proportional hazards models were used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs).

RESULTS

We identified 333 incident MI events, 321 incident stroke events and 771 deaths (154 with coronary heart disease [CHD] as underlying cause) during follow-up of up to 15 years. The multivariable HRs comparing >3 servings/week with ≤3 servings/month were 0.60 (95% CI, 0.39-0.92) for MI and 1.04 (95% CI, 0.66-1.64) for stroke. HRs for total mortality were lowest for moderate fish consumption of 1-<2 servings/week (0.82; 95% CI, 0.64-1.04) and 2-3 servings/week (0.79; 95% CI, 0.61-1.01) compared with ≤3 servings/month. The corresponding HRs for CHD-related mortality were 0.53; 95% CI, 0.32-0.90 and 0.75; 95% CI, 0.45-1.27.

CONCLUSIONS

Fish consumption was associated with lower MI incidence among individuals with type 2 diabetes, whereas no association was observed with stroke. Our data further indicated an association with lower mortality, particularly for CHD-related deaths. These findings support the current general advice on regular fish consumption also in the high risk group of type 2 diabetes patients.

No association between fish consumption and risk of stroke in the Spanish cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Spain): a 13·8-year follow-up study

OBJECTIVE

To prospectively assess the associations between lean fish, fatty fish and total fish intakes and risk of stroke in the Spanish cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Spain).

DESIGN

Fish intake was estimated from a validated dietary questionnaire. Cox proportional hazards regression models were used to assess the association between the intakes of lean fish, fatty fish and total fish and stroke risk. Models were run separately for men and women.

SETTING

Five Spanish regions (Asturias, San Sebastian, Navarra, Granada and Murcia).

SUBJECTS

Individuals (n 41 020; 15 490 men and 25 530 women) aged 20-69 years, recruited from 1992 to 1996 and followed-up until December 2008 (December 2006 in the case of Asturias). Only participants with definite incident stroke were considered as cases.

RESULTS

During a mean follow-up of 13·8 years, 674 strokes were identified and subsequently validated by record linkage with hospital discharge databases, primary-care records and regional mortality registries, comprising 531 ischaemic, seventy-nine haemorrhagic, forty-two subarachnoid and twenty-two unspecific strokes. After multiple adjustments, no significant associations were observed between lean fish, fatty fish and total fish consumption and the risk of stroke in men or women. In men, results revealed a non-significant trend towards an inverse association between lean fish (hazard ratio=0·84; 95 % CI 0·55, 1·29, P trend=0·06) and total fish consumption (hazard ratio=0·77; 95 % CI 0·51, 1·16, P trend=0·06) and risk of total stroke.

CONCLUSIONS

In the EPIC-Spain cohort, no association was found between lean fish, fatty fish and total fish consumption and risk of stroke.

Fish consumption and risk of stroke: a second prospective case-control study from northern Sweden

Background

Fish consumption has been concluded to be associated with decreased risk of stroke in several reviews. However, among men, but not women, an increased risk of stroke was previously found at high fish consumption (>3 meals/week) in northern Sweden. This study investigates if previous results on elevated stroke risk with high fish consumption in men in northern Sweden can be confirmed in a larger study with new cases in the same population.

Methods

A prospective nested case-control study was performed within the population-based Northern Sweden Health and Disease Study cohort. Information on fish consumption, other lifestyle and medical data was collected at baseline. Incident stroke cases (1987–2007, n = 735) were identified and 2698 controls matched for gender, age, year of baseline and geographical region.

Results

There were no associations between total fish or fatty fish consumption and stroke risk; thus the previous finding of increased risk of stroke with high fish consumption in men could not be repeated. High intake of lean fish (>twice/week compared to < once/month) was associated with increased stroke risk in men [OR 1.80 (95% CI 1.00, 3.21), but not in women [OR 0.50 (95% CI 0.24, 1.10)]. The association was driven by men living alone.

Conclusions

The previous association between high total fish consumption and risk of stroke in men could not be repeated. The increased risk found in men with high intake of lean fish may be due to chance or confounding specific for this group.

Electronic supplementary material

The online version of this article (doi:10.1186/s12937-016-0216-3) contains supplementary material, which is available to authorized users.

Associations of dietary polychlorinated biphenyls and long-chain omega-3 fatty acids with stroke risk

BACKGROUND

Little is known about joint exposure to polychlorinated biphenyls (PCBs) and long-chain omega-3 fatty acids [eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA)], through fish consumption, on cerebrovascular disease risk.

OBJECTIVE

To explore associations of dietary PCB exposure and EPA-DHA intake with risk of different stroke subtypes.

METHODS

This was assessed in the prospective population-based Cohort of Swedish Men including 39,948, middle-aged and elderly men, who were free of cardiovascular disease and cancer at baseline in 1997. Validated estimates of dietary PCBs and EPA-DHA were obtained via a food frequency questionnaire.

RESULTS

During 12years of follow-up, 2286 and 474 incident cases of ischemic stroke and hemorrhagic stroke, respectively, were ascertained through register linkage. Dietary PCB exposure and EPA-DHA intake were associated with hemorrhagic stroke but not ischemic stroke. Men in the highest quartile of dietary PCB exposure (median 412ng/day) had a multivariable- and EPA-DHA-adjusted RR of hemorrhagic stroke of 2.77 [95% confidence interval (CI), 1.48-5.19] compared with men in the lowest quartile (median 128ng/day; p for trend <0.01). The corresponding RRs in men with and without hypertension were 5.45 (95% CI, 1.34-22.1) and 2.37 (95% CI 1.17-4.79), respectively. The multivariable- and PCB-adjusted RR of hemorrhagic stroke for the highest quartile of EPA-DHA intake (median 0.73g/day) versus the lowest quartile (median 0.18g/day) was 0.42 (95% CI, 0.22-0.79).

CONCLUSION

Dietary PCB exposure was associated with an increased risk of hemorrhagic stroke, whereas a protective association was observed for dietary EPA-DHA intake.

Oily fish consumption is inversely correlated with cerebral microbleeds in community-dwelling older adults: results from the Atahualpa Project

BACKGROUND

Oily fish is a major dietary source of omega-3 polyunsaturated fatty acids (ω-3 PUFAs). These nutrients improve endothelial dysfunction, reduce β-amyloid induced damage of neurovascular units, and might prevent the occurrence of cerebral microbleeds. However, this relationship has not been investigated so far.

AIM

To evaluate the association between oily fish intake and cerebral microbleeds in a population of frequent fish consumers living in coastal Ecuador.

METHODS

Cerebral microbleeds were identified by gradient-echo MRI and oily fish consumption was calculated in community-dwellers aged ≥60 years enrolled in the Atahualpa Project. The association between cerebral microbleeds and fish servings was examined in regression models adjusted for relevant confounders. A predictive model was constructed using quintiles of fish servings to take into account the non-linearity in the relationship.

RESULTS

Out of 311 eligible individuals, 293 (94 %) were enrolled. Cerebral microbleeds were recognized in 37 (13 %) individuals. Mean fish consumption was 8.8 ± 5.4 servings per week (ω-3 PUFAs estimates: 10.2 ± 7.1 g). Multivariate analysis showed an inverse relationship between cerebral microbleeds and fish consumption (p < 0.001). Predictive margins of CMB were higher for individuals in the lowest (≤4.3) than for those in the highest (≥13.1) quintile of fish servings (17.4 vs 2.3 %, p < 0.001).

CONCLUSIONS

This study shows a lower cerebral microbleed presence among older adults eating large amounts of oily fish (13 servings per week, equivalent to about 15 g of ω-3 PUFAs). These high requirements can be more readily accomplished in other populations by taking fish oil preparations. Longitudinal studies are warranted to assess whether these interventions reduce incident cerebral microbleeds in high-risk individuals.

The 2015 Dutch food-based dietary guidelines

The objective of this study was to derive food-based dietary guidelines for the Dutch population. The dietary guidelines are based on 29 systematic reviews of English language meta-analyses in PubMed summarizing randomized controlled trials and prospective cohort studies on nutrients, foods and food patterns and the risk of 10 major chronic diseases: coronary heart disease, stroke, heart failure, diabetes, breast cancer, colorectal cancer, lung cancer, chronic obstructive pulmonary disease, dementia and depression. The committee also selected three causal risk factors for cardiovascular diseases or diabetes: systolic blood pressure, low-density lipoprotein cholesterol and body weight. Findings were categorized as strong or weak evidence, inconsistent effects, too little evidence or effect unlikely for experimental and observational data separately. Next, the committee selected only findings with a strong level of evidence for deriving the guidelines. Convincing evidence was based on strong evidence from the experimental data either or not in combination with strong evidence from prospective cohort studies. Plausible evidence was based on strong evidence from prospective cohort studies only. A general guideline to eat a more plant food-based dietary pattern and limit consumption of animal-based food and 15 specific guidelines have been formulated. There are 10 new guidelines on legumes, nuts, meat, dairy produce, cereal products, fats and oils, tea, coffee and sugar-containing beverages. Three guidelines on vegetables, fruits, fish and alcoholic beverages have been sharpened, and the 2006 guideline on salt stayed the same. A separate guideline has been formulated on nutrient supplements. Completely food-based dietary guidelines can be derived in a systematic and transparent way.

Plant-Based Dietary Patterns and Incidence of Type 2 Diabetes in US Men and Women: Results from Three Prospective Cohort Studies

BACKGROUND

Plant-based diets have been recommended to reduce the risk of type 2 diabetes (T2D). However, not all plant foods are necessarily beneficial. We examined the association of an overall plant-based diet and hypothesized healthful and unhealthful versions of a plant-based diet with T2D incidence in three prospective cohort studies in the US.

METHODS AND FINDINGS

We included 69,949 women from the Nurses' Health Study (1984-2012), 90,239 women from the Nurses' Health Study 2 (1991-2011), and 40,539 men from the Health Professionals Follow-Up Study (1986-2010), free of chronic diseases at baseline. Dietary data were collected every 2-4 y using a semi-quantitative food frequency questionnaire. Using these data, we created an overall plant-based diet index (PDI), where plant foods received positive scores, while animal foods (animal fats, dairy, eggs, fish/seafood, poultry/red meat, miscellaneous animal-based foods) received reverse scores. We also created a healthful plant-based diet index (hPDI), where healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, vegetable oils, tea/coffee) received positive scores, while less healthy plant foods (fruit juices, sweetened beverages, refined grains, potatoes, sweets/desserts) and animal foods received reverse scores. Lastly, we created an unhealthful plant-based diet index (uPDI) by assigning positive scores to less healthy plant foods and reverse scores to healthy plant foods and animal foods. We documented 16,162 incident T2D cases during 4,102,369 person-years of follow-up. In pooled multivariable-adjusted analysis, both PDI and hPDI were inversely associated with T2D (PDI: hazard ratio [HR] for extreme deciles 0.51, 95% CI 0.47-0.55, p trend < 0.001; hPDI: HR for extreme deciles 0.55, 95% CI 0.51-0.59, p trend < 0.001). The association of T2D with PDI was considerably attenuated when we additionally adjusted for body mass index (BMI) categories (HR 0.80, 95% CI 0.74-0.87, p trend < 0.001), while that with hPDI remained largely unchanged (HR 0.66, 95% CI 0.61-0.72, p trend < 0.001). uPDI was positively associated with T2D even after BMI adjustment (HR for extreme deciles 1.16, 95% CI 1.08-1.25, p trend < 0.001). Limitations of the study include self-reported diet assessment, with the possibility of measurement error, and the potential for residual or unmeasured confounding given the observational nature of the study design.

CONCLUSIONS

Our study suggests that plant-based diets, especially when rich in high-quality plant foods, are associated with substantially lower risk of developing T2D. This supports current recommendations to shift to diets rich in healthy plant foods, with lower intake of less healthy plant and animal foods.

New insights into the role of nutrition in CVD prevention

Nutrition plays an increasingly significant role in lifestyle strategies for cardiovascular prevention. Foods and dietary patterns that encompass specific foods and beverages and their combinations, with synergies among their components, are the subject of much epidemiologic and clinical research in relation to health issues, including cardiovascular disease. Foods with the highest evidence for beneficial effects on cardiovascular outcomes (mainly fatal and nonfatal coronary artery disease and stroke) and intermediate risk markers (principally cholesterol and blood pressure) are fruits and vegetables, legumes, nuts, whole grains, dairy products, fish, and alcohol consumed in moderation. Epidemiologic and clinical trial evidence on cardiovascular health issues is reviewed for these foods and for the dietary pattern with the highest probability of a causal link with cardiovascular protection, namely the Mediterranean diet. When pertinent, mechanisms of protection derived from specific nutrients in foods are also examined. The explosion of knowledge in cardioprotective foods and diets needs to be translated to the public, as dietary quality is still far from optimal in large segments of the population.

Association of Dietary Protein Consumption With Incident Silent Cerebral Infarcts and Stroke: The Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND AND PURPOSE

The effect of dietary protein on the risk of stroke has shown inconsistent results. We aimed to evaluate the relationship of dietary protein sources with the risk of stroke and silent cerebral infarcts in a large community-based cohort.

METHODS

We studied 11601 adults (age, 45-64 years at baseline in 1987-1989) enrolled in the Atherosclerosis Risk in Communities (ARIC) Study, free of diabetes mellitus and cardiovascular disease. Dietary protein intake was assessed with validated food frequency questionnaires at baseline and after 6 years of follow-up. Incident stroke events were identified through hospital discharge codes and stroke deaths and physician-adjudicated through December 31, 2011. A subset of participants (n=653) underwent brain magnetic resonance imaging in 1993 to 1995 and in 2004 to 2006. Cox proportional hazard models and logistic regression were used for statistical analyses.

RESULTS

During a median follow-up of 22.7 years, there were 699 stroke events. In multivariable analyses, total, animal, and vegetable protein consumption was not associated with risk of stroke. Red meat consumption was associated with increased stroke risk, particularly ischemic events. The hazard ratios (95% confidence interval) for risk of ischemic stroke across ascending quintiles of red meat consumption were 1 (ref), 1.13 (0.85-1.49), 1.44 (1.09-1.90), 1.33 (0.99-1.79), and 1.47 (1.06-2.05); Ptrend=0.01. No association of major dietary protein sources with silent cerebral infarcts was detected.

CONCLUSIONS

This study supports the notion that consumption of red meat may increase the risk of ischemic stroke. No association between dietary protein intake and silent cerebral infarcts was found.

ω-3 Fatty Acids and Cardiovascular Diseases: Effects, Mechanisms and Dietary Relevance

ω-3 fatty acids (n-3 FA) have, since the 1970s, been associated with beneficial health effects. They are, however, prone to lipid peroxidation due to their many double bonds. Lipid peroxidation is a process that may lead to increased oxidative stress, a condition associated with adverse health effects. Recently, conflicting evidence regarding the health benefits of intake of n-3 from seafood or n-3 supplements has emerged. The aim of this review was thus to examine recent literature regarding health aspects of n-3 FA intake from fish or n-3 supplements, and to discuss possible reasons for the conflicting findings. There is a broad consensus that fish and seafood are the optimal sources of n-3 FA and consumption of approximately 2-3 servings per week is recommended. The scientific evidence of benefits from n-3 supplementation has diminished over time, probably due to a general increase in seafood consumption and better pharmacological intervention and acute treatment of patients with cardiovascular diseases (CVD).

Choline and Betaine Intakes Are Not Associated with Cardiovascular Disease Mortality Risk in Japanese Men and Women

BACKGROUND

Dietary intakes of betaine and choline may reduce the risk of cardiovascular disease; however, epidemiologic evidence is limited. Seafood is a rich source of betaine and is a popular traditional food in Japan.

OBJECTIVE

We examined the associations of betaine and choline intakes with cardiovascular disease mortality in a population-based cohort study in Japan.

METHODS

Study subjects were 13,355 male and 15,724 female residents of Takayama City, Japan, who were aged ≥35 y and enrolled in 1992. Their diets were assessed by a validated food frequency questionnaire. Deaths from coronary heart disease and stroke were identified from death certificates over 16 y. Multivariable-adjusted HRs were computed by using Cox regression models.

RESULTS

During follow-up, we documented 308 deaths from coronary heart disease and 676 deaths from stroke (393 from ischemic and 153 from hemorrhagic strokes). Compared with the lowest quartile, the second, third, and highest quartiles of betaine intake were significantly associated with a decreased risk of mortality from coronary heart disease in men after controlling for covariates. The HRs were 0.58 (95% CI: 0.36, 0.93), 0.62 (95% CI: 0.39, 0.998), and 0.60 (95% CI: 0.37, 0.97), respectively. The trend was not statistically significant (P = 0.08). There was no significant association between betaine intake and the risk of mortality from ischemic stroke. In women, betaine intake was unrelated risk of mortality from coronary heart disease and stroke (P = 0.32 and 0.73, respectively, for interaction by sex). There was no significant association between choline intake and cardiovascular disease mortality risk in men or women.

CONCLUSION

Overall, we found no clear evidence of significant associations between choline and betaine intakes and cardiovascular disease mortality risk in Japanese men and women.

Fish consumption and risk of myeloma: a meta-analysis of epidemiological studies

PURPOSE

The relationship between fish consumption and multiple myeloma (MM) risk has not been consistent across epidemiological studies. We quantitatively assessed the aforementioned association through a systematic review and meta-analysis.

METHODS

PubMed was searched through the end of March 2015 for eligible studies. Fixed or random effects models were used to pool risk estimates. Five case-control studies that involved 1,366 cases and 8,259 controls were identified. Three studies had high methodological quality, and two studies had low quality based on the Newcastle-Ottawa Quality Assessment Scale.

RESULTS

After pooling all risk estimates, a significant inverse association was found between the highest category versus lowest category of fish consumption and MM risk (relative risk = 0.65, 95% confidence interval = 0.46-0.91), with relatively high heterogeneity (I(2) = 55.6%). No evidence of publication bias was detected. The inverse association persisted in all subgroups according to study quality, type, location, and whether there were adjustments for confounders, although statistical significance was not detected in all strata. The dose-response analysis suggested a nonlinear dose-response relationship for the association, with the lowest risk linked to fish consumption once per week.

CONCLUSION

This meta-analysis suggests that the highest versus lowest category of fish consumption is inversely associated with MM risk. Furthermore, a nonlinear dose-response relationship was suggested for the association. Because this evidence is based on a small number of retrospective studies with mixed quality and because high heterogeneity was detected, further prospective studies are warranted to validate our findings and better characterize the relationship.

The autonomic nervous system and cardiovascular disease: role of n-3 PUFAs

In the last decades, a large body of experimental and clinical evidence has been accumulated showing that cardiovascular diseases are often accompanied by an imbalance in the sympathetic-vagal outflow to the heart, resulting in a chronic adrenergic activation. The arterial baroreceptor system is a key component of mechanisms contributing to the neural regulation of the cardiovascular system. Several methods have been proposed to assess autonomic activity by analyzing heart rate and blood pressure changes either spontaneously occurring or following provocations. The autonomic nervous system has been regarded as one of the putative mechanisms involved into the beneficial effects of exposure to n-3 fatty acids observed in epidemiological studies. The aim of the present review is to provide an update on the clinical evidence proposed so far linking exposure to n-3 fatty acids to autonomic nervous system modulation.

The case for diet: a safe and efficacious strategy for secondary stroke prevention

Diet is strongly associated with risk for first stroke. In particular, observational and experimental research suggests that a Mediterranean-type diet may reduce risk for first ischemic stroke with an effect size comparable to statin therapy. These data for first ischemic stroke suggest that diet may also be associated with risk for recurrent stroke and that diet modification might represent an effective intervention for secondary prevention. However, research on dietary pattern after stroke is limited and direct experimental evidence for a therapeutic effect in secondary prevention does not exist. The uncertain state of science in this area is reflected in recent guidelines on secondary stroke prevention from the American Heart Association, in which the Mediterranean-type diet is listed with only a class IIa recommendation (level of evidence C). To change guidelines and practice, research is needed, starting with efforts to better define current nutritional practices of stroke patients. Food frequency questionnaires and mobile applications for real-time recording of intake are available for this purpose. Dietary strategies for secondary stroke prevention are low risk, high potential, and warrant further evaluation.

Fish consumption and mortality in the European Prospective Investigation into Cancer and Nutrition cohort

Fish is a source of important nutrients and may play a role in preventing heart diseases and other health outcomes. However, studies of overall mortality and cause-specific mortality related to fish consumption are inconclusive. We examined the rate of overall mortality, as well as mortality from ischaemic heart disease and cancer in relation to the intake of total fish, lean fish, and fatty fish in a large prospective cohort including ten European countries. More than 500,000 men and women completed a dietary questionnaire in 1992-1999 and were followed up for mortality until the end of 2010. 32,587 persons were reported dead since enrolment. Hazard ratios and their 99% confidence interval were estimated using Cox proportional hazard regression models. Fish consumption was examined using quintiles based on reported consumption, using moderate fish consumption (third quintile) as reference, and as continuous variables, using increments of 10 g/day. All analyses were adjusted for possible confounders. No association was seen for fish consumption and overall or cause-specific mortality for both the categorical and the continuous analyses, but there seemed to be a U-shaped trend (p < 0.000) with fatty fish consumption and total mortality and with total fish consumption and cancer mortality (p = 0.046).

Associations between food and beverage groups and major diet-related chronic diseases: an exhaustive review of pooled/meta-analyses and systematic reviews

Associations between food and beverage groups and the risk of diet-related chronic disease (DRCD) have been the subject of intensive research in preventive nutrition. Pooled/meta-analyses and systematic reviews (PMASRs) aim to better characterize these associations. To date, however, there has been no attempt to synthesize all PMASRs that have assessed the relationship between food and beverage groups and DRCDs. The objectives of this review were to aggregate PMASRs to obtain an overview of the associations between food and beverage groups (n = 17) and DRCDs (n = 10) and to establish new directions for future research needs. The present review of 304 PMASRs published between 1950 and 2013 confirmed that plant food groups are more protective than animal food groups against DRCDs. Within plant food groups, grain products are more protective than fruits and vegetables. Among animal food groups, dairy/milk products have a neutral effect on the risk of DRCDs, while red/processed meats tend to increase the risk. Among beverages, tea was the most protective and soft drinks the least protective against DRCDs. For two of the DRCDs examined, sarcopenia and kidney disease, no PMASR was found. Overweight/obesity, type 2 diabetes, and various types of cardiovascular disease and cancer accounted for 289 of the PMASRs. There is a crucial need to further study the associations between food and beverage groups and mental health, skeletal health, digestive diseases, liver diseases, kidney diseases, obesity, and type 2 diabetes.

Arachidonic Acid and Cerebral Ischemia Risk: A Systematic Review of Observational Studies

Background

Arachidonic acid (ARA) is a precursor of various lipid mediators. ARA metabolites such as thromboxane A₂ cause platelet aggregation and vasoconstriction, thus may lead to atherosclerotic disease. It is unclear whether dietary ARA influences the ARA-derived lipid mediator balance and the risk for atherosclerotic diseases, such as cerebral ischemia. Considering the function of ARA in atherosclerosis, it is reasonable to focus on the atherothrombotic type of cerebral ischemia risk. However, no systematic reviews or meta-analyses have been conducted to evaluate the effect of habitual ARA exposure on cerebral ischemia risk. We aimed to systematically evaluate observational studies available on the relationship between ARA exposure and the atherothrombotic type of cerebral ischemia risk in free-living populations.

Summary

The PubMed database was searched for articles registered up to June 24, 2014. We designed a PubMed search formula as follows: key words for humans AND brain ischemia AND study designs AND ARA exposure. Thirty-three articles were reviewed against predefined criteria. There were 695 bibliographies assessed from the articles that included both ARA and cerebral ischemia descriptions. Finally, we identified 11 eligible articles and categorized them according to their reporting and methodological quality. We used the Strengthening the Reporting of Observational Studies in Epidemiology Statement (STROBE) checklist to score the reporting quality. The methodological quality was qualitatively assessed based on the following aspects: subject selection, ARA exposure assessment, outcome diagnosis, methods for controlling confounders, and statistical analysis. We did not conduct a meta-analysis due to the heterogeneity among the studies. All eligible studies measured blood ARA levels as an indicator of exposure. Our literature search did not identify any articles that evaluated dietary ARA intake and tissue ARA as assessments of exposure. Seven of the 11 eligible articles were considered to be of low quality. No articles reported a dose-dependent positive association between an increased cerebral ischemia risk and ARA exposure. However, most studies did not assess the risk in each subtype of cerebral ischemia, thus various etiological types of cerebral ischemia risk were involved in their results.

Key Messages

We did not find a positive association between ARA exposure and cerebral ischemia risk. Eligible studies reported inconsistent findings: cerebral ischemia risk did not change or significantly decreased. We could not draw any conclusions due to the limited number of eligible high-quality studies. Further evidence from well-designed observational studies is required. Simultaneously, in order to develop effective preventive measures against cerebral ischemia, it is imperative to establish standardized definitions, nomenclatures, classifications, and diagnostic procedures.

Omega-3 polyunsaturated fatty acids and cardiovascular disease: an emphasis on omega-3-acid ethyl esters 90 for the treatment of hypertriglyceridemia

A number of epidemiological/observational studies, as well as large-scale randomized intervention studies, have been conducted to provide evidence for the efficacy of ω-3 fatty acids against atherosclerotic diseases. Currently, ω-3 fatty acids are commercially available in many parts of the world containing the same active ingredients as Lotriga(®) (ω-3-acid ethyl esters 90 [O3AE highly concentrated ω-3 fatty acid ethyl esters, consisting of eicosapentaenoic acid-ethyl ester and docosahexaenoic acid-ethyl ester [EPA-E/DHA-E]). A recent head-to-head comparative study of O3AEE90 versus EPA-E demonstrated that O3AEE90 4g/day led to a significantly greater reduction in triglycerides (TG) than EPA-E 1.8g/day and that O3AEE90 2g/day produced comparable effects on TG to those with EPA-E 1.8g/day. While both agents were shown to be useful in lowering TG, the hallmark feature of O3AEE90, that is, the presence of the DHA-E component versus its absence in EPA-E, needs to be further examined for its clinical implications.

Fish consumption and acute coronary syndrome: a meta-analysis

BACKGROUND

Findings on the association between fish consumption and acute coronary syndrome are inconsistent. We assessed the role of fish consumption in acute coronary syndrome by conducting a dose-response meta-analysis.

METHODS

We conducted a literature search of MEDLINE and Embase databases from 1966 to June 2013 for prospective cohort and case-control studies that evaluated the association between fish consumption and acute coronary syndrome among general populations without cardiovascular disease history. Additional studies were identified via hand search of references of relevant articles. Estimates of relative risk (RR) were pooled using random-effects model. Sex and age effects were also evaluated.

RESULTS

Our search retrieved 11 prospective cohort and 8 case-control studies, totaling 408,305 participants. Among prospective cohort studies, the highest category of fish consumption (ie, ≥4 times per week) was associated with the greatest risk reduction in acute coronary syndrome (RR 0.79; 95% confidence interval [CI], 0.70-0.89). In dose-response analysis, each additional 100-g serving of fish per week was associated with a 5% reduced risk (RR per serving 0.95; 95% CI, 0.92-0.97). Subgroup analysis and meta-regression suggested that the risk reduction did not differ across sex or age groups. No heterogeneity was observed among prospective cohort (P = .73) and case-control (P = .29) studies. There was no evidence of publication bias.

CONCLUSION

Our meta-analysis demonstrated that there is an inverse association between fish consumption and the risk of acute coronary syndrome. Fish consumption appears beneficial in the primary prevention of acute coronary syndrome, and higher consumption is associated with greater protection.

Update on cardiometabolic health effects of ω-3 fatty acids

PURPOSE OF REVIEW

The fish fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may promote cardiometabolic health. This review summarizes the results of recent meta-analyses of prospective studies on cardiovascular diseases, diabetes type 2 and markers of atherosclerosis and thrombosis.

RECENT FINDINGS

The results of recently published meta-analyses of prospective cohort studies showed that eating fish once a week was associated with a 16% lower risk of fatal coronary heart disease (CHD) and a 14% lower risk of stroke incidence, but was not related to heart failure. Fish consumption may be associated with a higher risk of diabetes in Western countries and a lower risk in Asian countries. Recent meta-analyses of randomized controlled trials showed that EPA-DHA supplementation reduced the risk of fatal CHD and sudden death by 10% of which the latter was not significant. Extra EPA-DHA did not reduce the risk of heart failure, stroke and cardiac arrhythmias. ω-3 fatty acid (FA) supplementation did reduce markers of ventricular fibrillation, inflammation and endothelial dysfunction and platelet aggregation.

SUMMARY

There is strong evidence for a protective effect of ω-3 FA on fatal CHD and for some markers of atherosclerosis and thrombosis. Consistent results were not obtained for other vascular diseases and diabetes. ω-3 FA reduced markers of ventricular fibrillation but did not reduce the risk of atrial fibrillation.

Omega-3 fatty acids and cardiovascular disease: epidemiology and effects on cardiometabolic risk factors

Clinical and epidemiological studies provide support that the polyunsaturated omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid from fish and fish oils are cardioprotective, particularly in the setting of secondary prevention.

Dietary n-3 PUFA and CVD: a review of the evidence

Many clinical and epidemiological studies have shown that the polyunsaturated n-3 fatty acids EPA and DHA from fish and fish oils, provide cardiovascular protection, particularly in the setting of secondary prevention. n-3 Fatty acids beneficially influence a number of cardiometabolic risk factors including blood pressure, cardiac function, vascular reactivity and lipids, as well as having anti-platelet, anti-inflammatory and anti-oxidative actions. They do not appear to adversely interact with other medications such as statins and other lipid-lowering drugs or antihypertensive medications. n-3 Fatty acids have gained widespread usage by general practitioners and clinicians in a number of clinical settings such as pregnancy and infant development, secondary prevention in CHD patients, treatment of dyslipidaemias and haemodialysis patients. Small doses are achievable with consumption of two to three oily fish meals per week or via purified encapsulated preparations now readily available. n-3 Fatty acids, particularly when consumed as fish, should be considered an important component of a healthy diet. The present paper reviews the effects of n-3 fatty acids on cardiometabolic risk factors, concentrating particularly on the evidence from randomised controlled studies in human subjects.

Fish consumption and the risk of myocardial infarction and stroke in the German arm of the European Prospective Investigation into Cancer and Nutrition (EPIC-Germany)

Recent meta-analyses have confirmed that fish consumption is related to decreased risks of ischaemic stroke and fatal CHD, while there seem to be no clear associations between fish consumption and the risks of haemorrhagic stroke and non-fatal CHD. As no studies in German populations have been reported to date, we assessed whether fish consumption as recorded by FFQ between 1994 and 1998 was related to incident myocardial infarction (MI) and stroke within the German arm of the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Cox proportional hazards regression analyses were conducted based on the data of 48 315 participants aged 35–65 years at baseline. The median fish intake was 16·4 g/d (25th–75th percentile 8·2–28·8 g/d). During a mean follow-up of 8·1 years, 605 incident MI and 525 incident strokes have been documented. After multiple adjustment, fish consumption was not related to incident MI (hazard ratio (HR) 0·84, 95 % CI 0·66, 1·08, Ptrend= 0·21) or stroke (HR 0·96, 95 % CI 0·73, 1·26, Ptrend= 0·67). Separate analyses for fatal MI, ischaemic stroke and haemorrhagic stroke did not show significant associations, either. With regard to non-fatal MI, there was a non-significant trend for an inverse association (HR 0·78, 95 % CI 0·59, 1·03, Ptrend= 0·07). Overall, fish consumption was not related to the risks of MI and stroke in the EPIC-Germany study.