The percentage of DHA in erythrocytes can detect non-adherence to advice to increase EPA and DHA intakes

Lipidomic and Fatty Acid Biomarkers in Whole Blood Can Predict the Dietary Intake of Eicosapentaenoic and Docosahexaenoic Acids in a Danish Population

BACKGROUND

The intake of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been associated with health benefits. Blood levels of these fatty acids, measured by gas chromatography (GC), are associated with their dietary intake, but the relationships with lipidomic measurements are not well defined.

OBJECTIVES

This study aimed to determine the lipidomic biomarkers in whole blood that predict intakes of EPA + DHA and examine the relationship between lipidomic and GC-based n-3 polyunsaturated fatty acid (n-3 PUFA) biomarkers.

METHODS

Lipidomic and fatty acid analyses were completed on 120 whole blood samples collected from Danish participants. Dietary intakes were completed using a web-based 7-d food diary. Stepwise multiple linear regression was used to identify the fatty acid and lipidomic variables that predict intakes of EPA + DHA and to determine lipidomic species that predict commonly used fatty acid biomarkers.

RESULTS

Stepwise regression selected lipidomic variables with an R2 = 0.52 for predicting EPA + DHA intake compared to R2 = 0.40 for the selected fatty acid GC-based variables. More predictive models were generated when the lipidomic variables were selected for females only (R2 = 0.62, n = 68) and males only (R2 = 0.72, n = 52). Phosphatidylethanolamine plasmalogen species containing EPA or DHA tended to be the most predictive lipidomic variables. Stepwise regression also indicated that selected lipidomic variables can predict commonly used fatty acid GC-based n-3 PUFA biomarkers as the R2 values ranged from 0.84 to 0.91.

CONCLUSIONS

Both fatty acid and lipidomic data can be used to predict EPA + DHA intakes, and fatty acid GC-based biomarkers can be emulated by lipidomic species. Lipidomic-based biomarkers appear to be influenced by sex differences, probably in n-3 PUFA and lipoprotein metabolism. These results improve our ability to understand the relationship between novel lipidomic data and GC fatty acid data and will increase our ability to apply lipidomic methods to fatty acid and lipid nutritional research.

Human milk fatty acid composition and its association with maternal blood and adipose tissue fatty acid content in a cohort of women from Europe

PURPOSE

Human milk (HM) composition is influenced by factors, like maternal diet and body stores, among other factors. For evaluating the influence of maternal fatty acid (FA) status on milk FA composition, the correlation between FA content in HM and in maternal plasma, erythrocytes, and adipose tissue was investigated.

METHODS

223 European women who delivered at term, provided HM samples over first four months of lactation. Venous blood and adipose tissue (only from mothers who consented and underwent a C-section delivery) were sampled at delivery. FAs were assessed in plasma, erythrocytes, adipose tissue, and HM. Evolution of HM FAs over lactation and correlations between FA content in milk and tissues and between mother's blood and cord blood were established.

RESULTS

During lactation, arachidonic acid (ARA) and docosahexaenoic acid (DHA) significantly decreased, while linoleic acid (LA), alpha-linolenic acid (ALA), and eicosapentaenoic acid (EPA) remained stable. Positive correlations were observed between HM and adipose tissue for palmitic, stearic, oleic, and polyunsaturated fatty acids (PUFAs). Correlations were found between milk and plasma for oleic, LA, ARA, ALA, DHA, monounsaturated fatty acids (MUFAs), and PUFAs. No correlation was observed between erythrocytes and HM FAs. LA and ALA were more concentrated in maternal blood than in infant blood, contrary to ARA and DHA, supporting that biomagnification of LCPUFAs may have occurred during pregnancy.

CONCLUSIONS

These data show that maternal adipose tissue rather than erythrocytes may serve as reservoir of PUFAs and LCPUFAs for human milk. Plasma also supplies PUFAs and LCPUFAs to maternal milk. If both, adipose tissue and plasma PUFAs, are reflection of dietary intake, it is necessary to provide PUFAs and LCPUFAs during pregnancy or even before conception and lactation to ensure availability for mothers and enough supply for the infant via HM.

Role of n-3 long-chain polyunsaturated fatty acids in human nutrition and health: review of recent studies and recommendations

Long-chain (LC) n-3 polyunsaturated fatty acids (n-3 PUFAs), in particular docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), are nutrients involved in many metabolic and physiological processes, and are referred to as n-3 LCPUFA. They have been extensively studied for their effects in human nutrition and health. This paper provides an overview on metabolism, sources, dietary intake, and status of n-3 LCPUFA. A summary of the dietary recommendations for n-3 LCPUFAs for different age groups as well as specific physiological conditions is provided. Evidence for n-3 LCPUFA in cardiovascular diseases, including new studies, is reviewed. Expert recommendations generally support a beneficial effect of n-3 LCPUFA on cardiovascular health and recommend a daily intake of 500 mg as DHA and EPA, or 1-2 servings of fish per week. The role of n-3 LCPUFA on brain health, in particular neurodegenerative disorders and depression, is reviewed. The evidence for beneficial effects of n-3 LCPUFA on neurodegenerative disorders is non-conclusive despite mechanistic support and observational data. Hence, no definite n-3 LCPUFA expert recommendations are made. Data for the beneficial effect of n-3 LCPUFA on depression are generally compelling. Expert recommendations have been established: 200-300 mg/day for depression; up to 1-2 g/day for major depressive disorder. Recent studies support a beneficial role of n-3 LCPUFAs in reducing the risk for premature birth, with a daily intake of 600-800 mg of DHA during pregnancy. Finally, international experts recently reviewed the scientific evidence on DHA and arachidonic acid (ARA) in infant nutrition and concluded that the totality of data support that infant and follow-on formulas should provide both DHA and ARA at levels similar to those in breast milk. In conclusion, the available scientific data support that dietary recommendations for n-3 LCPUFA should be established for the general population and for subjects with specific physiological conditions.

Dietary Reference Intakes based on chronic disease endpoints: outcomes from a case study workshop for omega 3's EPA and DHA

Given the focus on developing Dietary Reference Intakes (DRIs) based on chronic disease risk reduction and recent research for omega-3 long chain PUFA since the last DRI review, the Canadian Nutrition Society convened a panel of stakeholders for a 1-day workshop in late 2019. Attendees discussed the new NASEM guidelines for establishing DRI values based on chronic disease risk endpoints and the strength of current evidence for EPA and DHA as it relates to the new guidelines. Novelty: Summarizes evidence and expert opinions regarding the potential for reviewing DRI values for EPA and DHA and cardiovascular disease risk and early development.

Increased Omega-3 Fatty Acid Intake is Inversely Associated with Sarcopenic Obesity in Women but not in Men, Based on the 2014-2018 Korean National Health and Nutrition Examination Survey

(1) Background: Omega-3 fatty acids (ω3FAs) are known to improve protein anabolism, increase the sensitivity to anabolic stimuli, decrease lipogenesis, and stimulate lipid oxidation. We aim to investigate whether ω3FAs are associated with the prevalence of sarcopenic obesity (SO). (2) Methods: Data were obtained from the 2014–2018 Korean National Health and Nutrition Examination Survey. The ratio of daily ω3FA intake to energy intake (ω3FA ratio) was categorized into four quartile groups. (3) Results: The prevalence of SO from Q1 to Q4 was 8.9%, 11.3%, 11.0%, and 9.8% respectively, in men and 17.4%, 14.0%, 13.9%, and 10.1% respectively, in women. The ω3FA ratio in individuals with and without SO were 1.0% and 0.9% in men (p-value = 0.271) respectively, and 0.8% and 1.0% in women (p-value = 0.017), respectively. Compared with Q1, odds ratios (95% confidence intervals) of Q2, Q3, and Q4 of ω3FA ratios were 1.563 (0.802–3.047), 1.246 (0.611–2.542), and 0.924 (0.458–1.864) respectively, in men and 0.663 (0.379–1.160), 0.640 (0.372–1.102), and 0.246 (0.113–0.534) respectively, in women, after fully adjusting for confounding factors. (4) Conclusions: The ω3FA ratio was significantly higher in older females without SO than in older females with SO. The ω3FA ratio was associated with the prevalence of SO in elderly females.

Blood Metabolomic Profiling Confirms and Identifies Biomarkers of Food Intake

Metabolomics can be a tool to identify dietary biomarkers. However, reported food-metabolite associations have been inconsistent, and there is a need to explore further associations. Our aims were to confirm previously reported food-metabolite associations and to identify novel food-metabolite associations. We conducted a cross-sectional analysis of data from 849 participants (57% men) of the PopGen cohort. Dietary intake was obtained using FFQ and serum metabolites were profiled by an untargeted metabolomics approach. We conducted a systematic literature search to identify previously reported food-metabolite associations and analyzed these associations using linear regression. To identify potential novel food-metabolite associations, datasets were split into training and test datasets and linear regression models were fitted to the training datasets. Significant food-metabolite associations were evaluated in the test datasets. Models were adjusted for covariates. In the literature, we identified 82 food-metabolite associations. Of these, 44 associations were testable in our data and confirmed associations of coffee with 12 metabolites, of fish with five, of chocolate with two, of alcohol with four, and of butter, poultry and wine with one metabolite each. We did not identify novel food-metabolite associations; however, some associations were sex-specific. Potential use of some metabolites as biomarkers should consider sex differences in metabolism.

Biomarkers of meat and seafood intake: an extensive literature review

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

Compound-specific isotope analysis reveals no retroconversion of DHA to EPA but substantial conversion of EPA to DHA following supplementation: a randomized control trial

BACKGROUND

It has long been believed that DHA supplementation increases plasma EPA via the retroconversion pathway in mammals. However, in rodents this increase in EPA is likely due to a slower metabolism of EPA, but this has never been tested directly in humans.

OBJECTIVE

The aim of this study was to use the natural variations in 13C:12C ratio (carbon-13 isotopic abundance [δ13C]) of n-3 PUFA supplements to assess n-3 PUFA metabolism following DHA or EPA supplementation in humans.

METHODS

Participants (aged 21.6 ± 2.2 y) were randomly assigned into 1 of 3 supplement groups for 12 wk: 1) olive oil control, 2) ∼3 g/d DHA, or 3) ∼3 g/d EPA. Blood was collected before and after the supplementation period, and concentrations and δ13C of plasma n-3 PUFA were determined.

RESULTS

DHA supplementation increased (P < 0.05) plasma EPA concentrations by 130% but did not affect plasma δ13C-EPA (-31.0 ± 0.30 to -30.8 ± 0.19, milliUrey ± SEM, P > 0.05). In addition, EPA supplementation did not change plasma DHA concentrations (P > 0.05) but did increase plasma δ13C-DHA (-27.9 ± 0.2 to -25.6 ± 0.1, P < 0.05) toward δ13C-EPA of the supplement (-23.5 ± 0.22). EPA supplementation increased plasma concentrations of EPA and docosapentaenoic acid (DPAn-3) by 880% and 200%, respectively, and increased plasma δ13C-EPA (-31.5 ± 0.2 to -25.7 ± 0.2) and δ13C-DPAn-3 (-28.9 ± 0.3 to -25.0 ± 0.1) toward δ13C-EPA of the supplement.

CONCLUSIONS

In this study, we show that the increase in plasma EPA following DHA supplementation in humans does not occur via retroconversion, but instead from a slowed metabolism and/or accumulation of plasma EPA. Furthermore, substantial amounts of supplemental EPA can be converted into DHA. δ13C of n-3 PUFA in humans is a powerful and underutilized tool that can track dietary n-3 PUFA and elucidate complex metabolic questions. This trial was registered at clinicaltrials.gov as NCT03378232.

Erythrocyte membrane n-3 polyunsaturated fatty acids are inversely associated with the presence and progression of nonalcoholic fatty liver disease in Chinese adults: a prospective study

PURPOSE

Previous studies have shown that high-dose supplementation with n-3 polyunsaturated fatty acids (PUFAs) may benefit patients with nonalcoholic fatty liver disease (NAFLD), but the association of n-3 PUFAs with NAFLD among individuals with normal diets is only speculative. We investigated the cross-sectional and prospective associations between n-3 PUFAs and NAFLD in Chinese adults.

METHODS

This community-based prospective study included 3049 men and women (40-75 years) in Guangzhou, China, whose participants completed an NAFLD ultrasound evaluation and erythrocyte PUFA tests. A total of 2660 participants underwent the second NAFLD evaluation approximately 3 years later. α-Linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in erythrocytes were measured by gas chromatography.

RESULTS

After adjusting for potential confounders, we observed inverse associations between DHA, DHA + EPA, total n-3 PUFAs and the presence of NAFLD in the cross-sectional analysis. The adjusted odds ratios (95% confidence interval) of NAFLD for the highest (vs. lowest) tertile were 0.74 (0.61, 0.90) for DHA, 0.82 (0.67, 1.00) for EPA, 0.73 (0.60, 0.88) for DHA + EPA and 0.74 (0.61, 0.91) for total n-3 PUFAs  (all P values≤0.05). Over the average 3.12 years of follow-up, higher levels of DHA was associated with an improvement of NAFLD. The hazard ratio of improved NAFLD for the highest tertile was 1.18 (95% CI 1.09, 1.33) for DHA. Pathway analyses showed that favorable associations may be mediated by improvements in inflammatory markers (e.g., interleukin 1 beta and tumor necrosis factor alpha-like).

CONCLUSIONS

Erythrocyte membrane n-3 PUFAs are inversely associated with the presence and progression of NAFLD in Chinese adults.

TRIAL REGISTRATIONS

ClinicalTrials.gov NCT03179657.

Best practices for the design, laboratory analysis, and reporting of trials involving fatty acids

Fatty acids are among the most studied nutrients in human metabolism and health. Endogenous fatty acid status influences health and disease via multiple mechanisms at all stages of the life cycle. Despite widespread interest, attempts to summarize the results of multiple studies addressing similar fatty acid-related outcomes via meta-analyses and systematic reviews have been disappointing, largely because of heterogeneity in study design, sampling, and laboratory and data analyses. Our purpose is to recommend best practices for fatty acid clinical nutrition and medical studies. Key issues in study design include judicious choice of sampled endogenous pools for fatty acid analysis, considering relevant physiologic state, duration of intervention and/or observation, consideration of specific fatty acid dynamics to link intake and endogenous concentrations, and interpretation of results with respect to known fatty acid ranges. Key laboratory considerations include proper sample storage, use of sample preparation methods known to be fit-for-purpose via published validation studies, detailed reporting or methods to establish proper fatty acid identification, and quantitative analysis, including calibration of differential response, quality control procedures, and reporting of data on a minimal set of fatty acids to enable comprehensive interpretation. We present a checklist of recommendations for fatty acid best practices to facilitate design, review, and evaluation of studies with the intention of improving study reproducibility.

Effect of supplementation with flaxseed oil and different doses of fish oil for 2 weeks on plasma phosphatidylcholine fatty acids in young women

Background/objectives

Although assumed, it remains unclear that fatty acid (FA) biomarkers of n-3 long-chain PUFA reflect wide ranges of intake. However, to be utilised as biomarkers, to predict dietary intake, dose–response curves that cover a spectrum of intakes are required. The aim of the study was to investigate whether the FA composition of plasma phosphatidylcholine (PC) is a sensitive biomarker of n-3 FAs from fish oil, across a range of supplementation doses, and alpha-linolenic acid (ALA) supplementation, in young, healthy women.

Subjects/methods

A total of 303 young women were randomised to intakes ranging between 0.33 and 4.50 g EPA+DHA/day from fish oil (not all doses used in each year) or flaxseed oil (5.90–6.60 g/d) daily for 14 days in a series of trials, over 5 years. Fasting blood was collected at baseline (day 0) and day 14 and plasma PC FA composition, total and HDL-cholesterol and triglyceride concentrations measured.

Results

Fourteen days supplementation with fish oil significantly (P < 0.01) increased, in a dose-dependent fashion, plasma PC EPA, DPA and DHA at all doses except 1 and 3 mL/day. For the combined group of women who consumed any fish oil there was a 16% (P < 0.01) decrease in plasma triacylglycerol concentrations after 14 days supplementation. Flaxseed oil supplementation for 14 day resulted in significant (P < 0.01) increases in ALA, EPA and DPA, whilst DHA remained unchanged.

Conclusion

Our data demonstrate plasma PC is a sensitive biomarker of n-3 FA intake and reflects changes within 14 days across a range of intakes.

Validation of biomarkers of food intake-critical assessment of candidate biomarkers

Biomarkers of food intake (BFIs) are a promising tool for limiting misclassification in nutrition research where more subjective dietary assessment instruments are used. They may also be used to assess compliance to dietary guidelines or to a dietary intervention. Biomarkers therefore hold promise for direct and objective measurement of food intake. However, the number of comprehensively validated biomarkers of food intake is limited to just a few. Many new candidate biomarkers emerge from metabolic profiling studies and from advances in food chemistry. Furthermore, candidate food intake biomarkers may also be identified based on extensive literature reviews such as described in the guidelines for Biomarker of Food Intake Reviews (BFIRev). To systematically and critically assess the validity of candidate biomarkers of food intake, it is necessary to outline and streamline an optimal and reproducible validation process. A consensus-based procedure was used to provide and evaluate a set of the most important criteria for systematic validation of BFIs. As a result, a validation procedure was developed including eight criteria, plausibility, dose-response, time-response, robustness, reliability, stability, analytical performance, and inter-laboratory reproducibility. The validation has a dual purpose: (1) to estimate the current level of validation of candidate biomarkers of food intake based on an objective and systematic approach and (2) to pinpoint which additional studies are needed to provide full validation of each candidate biomarker of food intake. This position paper on biomarker of food intake validation outlines the second step of the BFIRev procedure but may also be used as such for validation of new candidate biomarkers identified, e.g., in food metabolomic studies.

A comparison of heart rate variability, n-3 PUFA status and lipid mediator profile in age- and BMI-matched middle-aged vegans and omnivores

Low heart rate variability (HRV) predicts sudden cardiac death. Long-chain (LC) n-3 PUFA (C20-C22) status is positively associated with HRV. This cross-sectional study investigated whether vegans aged 40-70 years (n 23), whose diets are naturally free from EPA (20 : 5n-3) and DHA (22 : 6n-3), have lower HRV compared with omnivores (n 24). Proportions of LC n-3 PUFA in erythrocyte membranes, plasma fatty acids and concentrations of plasma LC n-3 PUFA-derived lipid mediators were significantly lower in vegans. Day-time interbeat intervals (IBI), adjusted for physical activity, age, BMI and sex, were significantly shorter in vegans compared with omnivores (mean difference -67 ms; 95 % CI -130, -3·4, P50 % and high-frequency power) were similarly lower in vegans, with no differences during sleep. In conclusion, vegans have higher 24 h SDNN, but lower day-time HRV and shorter day-time IBI relative to comparable omnivores. Vegans may have reduced availability of precursor markers for pro-resolving lipid mediators; it remains to be determined whether there is a direct link with impaired cardiac function in populations with low-n-3 status.

Global survey of the omega-3 fatty acids, docosahexaenoic acid and eicosapentaenoic acid in the blood stream of healthy adults

Studies reporting blood levels of the omega-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), were systematically identified in order to create a global map identifying countries and regions with different blood levels. Included studies were those of healthy adults, published in 1980 or later. A total of 298 studies met all inclusion criteria. Studies reported fatty acids in various blood fractions including plasma total lipids (33%), plasma phospholipid (32%), erythrocytes (32%) and whole blood (3.0%). Fatty acid data from each blood fraction were converted to relative weight percentages (wt.%) and then assigned to one of four discrete ranges (high, moderate, low, very low) corresponding to wt.% EPA+DHA in erythrocyte equivalents. Regions with high EPA+DHA blood levels (>8%) included the Sea of Japan, Scandinavia, and areas with indigenous populations or populations not fully adapted to Westernized food habits. Very low blood levels (≤4%) were observed in North America, Central and South America, Europe, the Middle East, Southeast Asia, and Africa. The present review reveals considerable variability in blood levels of EPA+DHA and the very low to low range of blood EPA+DHA for most of the world may increase global risk for chronic disease.

Translating plasma and whole blood fatty acid compositional data into the sum of eicosapentaenoic and docosahexaenoic acid in erythrocytes

Specific blood levels of eicosapentaenoic plus docosahexaenoic acid (EPA+DHA, wt% of total) in erythrocytes or "the omega-3 index" have been recommended for cardio-protection, but fatty acids are often measured in different blood fractions. The ability to estimate the % of EPA+DHA in erythrocytes from the fatty acid composition of other blood fractions would enable clinical assessments of omega-3 status when erythrocyte fractions are not available and increase the ability to compare blood levels of omega-3 fatty acids across clinical studies. The fatty acid composition of baseline plasma, erythrocytes and whole blood samples from participants (n=1104) in a prospective, multicenter study examining acute coronary syndrome were determined. The ability to predict the % of EPA+DHA in erythrocytes from other blood fractions were examined using bivariate and multiple linear regression modelling. Concordance analysis was also used to compare the actual erythrocytes EPA+DHA values to values estimated from other blood fractions. EPA+DHA in erythrocytes was significantly (p<0.001) correlated EPA+DHA in plasma (r(2)=0.54) and whole blood (r(2)=0.79). Using multiple linear regression to predict EPA+DHA in erythrocytes resulted in stronger coefficients of determination in both plasma (R(2)=0.70) and whole blood (R(2)=0.84). Concordance analyses indicated agreement between actual and estimated EPA+DHA in erythrocytes, although estimating from plasma fatty acids appears to require translation by categorization rather than by translation as continuous data. This study shows that the fatty acid composition of different blood fractions can be used to estimate erythrocyte EPA+DHA in a population with acute coronary syndrome.

The stability of blood fatty acids during storage and potential mechanisms of degradation: A review

Fatty acids in blood samples, particularly polyunsaturated fatty acids (PUFAs), are susceptible to degradation through peroxidation reactions during long-term storage. Storage of blood samples is necessary in almost all studies and is crucial for larger clinical studies and in field research settings where it is not plausible for analytical infrastructure. Despite this, PUFA stability during blood storage is often overlooked. This review introduces and discusses lipid peroxidation and popular strategies employed to prevent or minimize peroxidation reactions during fatty acid analysis. Further, an in-depth examination of fatty acid stability during storage of blood is discussed in detail for all blood fractions including plasma/serum, erythrocytes and whole blood stored both in cryovials and on chromatography paper before discussing the associated mechanisms of degradation during storage. To our knowledge this is the first review of its kind and will provide researchers with the necessary information to confidently store blood samples for fatty acid analysis.

Omega-3 polyunsaturated fatty acid blood biomarkers increase linearly in men and women after tightly controlled intakes of 0.25, 0.5, and 1 g/d of EPA + DHA

Blood levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been related to coronary heart disease risk. Understanding the response of EPA + DHA in blood to dietary intake of EPA + DHA would facilitate the use of blood measures as markers of adherence and enable the development of dietary recommendations. The objective of this study is examine the blood response to intakes of EPA + DHA ≤1 g/d with an intervention designed for dietary adherence. It was hypothesized this relationship would be linear and that intakes of EPA + DHA <1 g/d would result in blood levels below those associated with the highest level of protection for cardiovascular events. Background EPA + DHA intake of men and women (n = 20) was determined by food frequency questionnaire and adherence was monitored by weekly fingertip blood sampling for fatty acid determinations. Participants consumed nutraceuticals to achieve intakes of 0.25 g/d and 0.5 g/d EPA + DHA for successive four-week periods. A subgroup (n = 5) had intakes of 1.0 g/d EPA + DHA for an additional 4 weeks. Fatty acid composition of whole blood, erythrocytes, and plasma phospholipids were determined at each time point. Blood levels of EPA and DHA increased linearly in these pools. A comprehensive review of the literature was used to verify the blood-intake relationship. Blood levels of long chain omega-3 polyunsaturated fatty acids reached blood levels associated with the highest levels of primary cardiac arrest reduction and sudden cardiac death risk only with intakes of 1.0 g/d of EPA + DHA. The blood biomarker response to intakes of EPA + DHA ≤1 g/d is linear in a small but highly adherent study sample and this information can assist in determining adherence in clinical studies and help identify dietary intake targets from associations between blood and disease.

Accuracy of self-reported intake of signature foods in a school meal intervention study: comparison between control and intervention period

Bias in self-reported dietary intake is important when evaluating the effect of dietary interventions, particularly for intervention foods. However, few have investigated this in children, and none have investigated the reporting accuracy of fish intake in children using biomarkers. In a Danish school meal study, 8- to 11-year-old children (n 834) were served the New Nordic Diet (NND) for lunch. The present study examined the accuracy of self-reported intake of signature foods (berries, cabbage, root vegetables, legumes, herbs, potatoes, wild plants, mushrooms, nuts and fish) characterising the NND. Children, assisted by parents, self-reported their diet in a Web-based Dietary Assessment Software for Children during the intervention and control (packed lunch) periods. The reported fish intake by children was compared with their ranking according to fasting whole-blood EPA and DHA concentration and weight percentage using the Spearman correlations and cross-classification. Direct observation of school lunch intake (n 193) was used to score the accuracy of food-reporting as matches, intrusions, omissions and faults. The reporting of all lunch foods had higher percentage of matches compared with the reporting of signature foods in both periods, and the accuracy was higher during the control period compared with the intervention period. Both Spearman's rank correlations and linear mixed models demonstrated positive associations between EPA+DHA and reported fish intake. The direct observations showed that both reported and real intake of signature foods did increase during the intervention period. In conclusion, the self-reported data represented a true increase in the intake of signature foods and can be used to examine dietary intervention effects.

Cryopreservation prevents iron-initiated highly unsaturated fatty acid loss during storage of human blood on chromatography paper at -20°C

BACKGROUND

Fingertip prick whole blood collection on chromatography paper is amenable to high-throughput fatty acid (FA) profiling for large clinical and field studies. However, sample storage is problematic because highly unsaturated FAs (HUFAs) in erythrocytes rapidly degrade in samples stored at -20°C.

OBJECTIVE

The aim of the current study was to determine the mechanism of HUFA degradation and to develop prevention protocols.

METHODS

Free fatty acid (FFA) standards and whole blood reference material from a single participant were used to examine sample storage at -20°C for up to 90 d in triplicate. Iron chelation with deferoxamine (0-5000 μg), antioxidant protection with butylated hydroxytoluene (50 μg), cryopreservation with glycerol, and blood drying were examined using whole blood on chromatography strips. Biological replicate blood samples from additional participants (n = 6) with a range of ω-3 (n-3) HUFA concentrations were similarly assessed.

RESULTS

FFAs were relatively stable when stored on chromatography strips at -20°C. Glycerol treatment prevented HUFA degradation in whole blood reference material for 30 d (45 ± 0.4 to 46.8 ± 0.1, means ± SDs) compared to untreated saline controls (45.9 ± 1.0 to 6.8 ± 0.2). Pretreatment of paper for blood spots with deferoxamine and drying blood before storage slowed, but not entirely prevented, HUFA degradation over 30 d to 22% and 19% below baseline, respectively, compared to 86-92% in the controls. Protection against HUFA degradation with blood drying and glycerol treatment was confirmed in the biological replicate study and confirmed by prevention of cell lysis.

CONCLUSIONS

HUFA degradation during storage at -20°C appears to be due to hemolysis and subsequent iron-initiated peroxidation. This degradation may be prevented by glycerol, iron chelation, and/or dried blood spotting. A more thorough understanding of methods to prevent degradation during storage is critical with increasing use of FA profiling in large clinical studies.

Omega-3 fatty acids and the genetic risk of early onset acute coronary syndrome

BACKGROUND AND AIMS

Recent gene-environment interaction studies suggest that diet may influence an individual's genetic predisposition to cardiovascular risk. We evaluated whether omega-3 fatty acid intake may influence the risk for acute coronary syndrome (ACS) conferred by genetic polymorphisms among patients with early onset ACS.

METHODS AND RESULTS

Our population consisted of 705 patients of white European descent enrolled in GENESIS-PRAXY, a multicenter cohort study of patients aged 18-55 years and hospitalized with ACS. We used a case-only design to investigate interactions between the omega-3 index (a validated biomarker of omega-3 fatty acid intake) and 30 single nucleotide polymorphisms (SNPs) robustly associated with ACS. We used logistic regression to assess the interaction between each SNP and the omega-3 index. Interaction was also assessed between the omega-3 index and a genetic risk score generated from the 30 SNPs. All models were adjusted for age and sex. An interaction for increased ACS risk was found between carriers of the chromosome 9p21 variant rs4977574 and low omega-3 index (OR 1.57, 95% CI 1.07-2.32, p = 0.02), but this was not significant after correction for multiple testing. Similar results were obtained in the adjusted model (OR 1.55, 95% CI 1.05-2.29, p = 0.03). We did not observe any interaction between the genetic risk score or any of the other SNPs and the omega-3 index.

CONCLUSION

Our results suggest that omega-3 fatty acid intake may modify the genetic risk conferred by chromosome 9p21 variation in the development of early onset ACS and requires independent replication.

Intrinsic heart rate recovery after dynamic exercise is improved with an increased omega-3 index in healthy males

Dietary fish consumption contributes to a reduced risk of cardiac mortality. In the present study, the effect of low-dose fish oil (FO) supplementation on heart rate (HR) response to intense exercise and recovery was investigated in physically fit males. The subjects (n 26) were supplemented (double-blind, parallel design) with (2 × 1 g/d) soya bean oil (control) or tuna FO providing the long-chain n-3 PUFA DHA (560 mg) and EPA (140 mg). Erythrocyte omega-3 index (%EPA+DHA), HR, HR variability and HR recovery were analysed during rest, intense exercise and recovery at baseline and after 8 weeks of supplementation. The mean erythrocyte omega-3 index, which did not differ between the groups at baseline (control 4·2 (sem 0·2), n 13; FO 4·7 (sem 0·2), n 13), remained unchanged in the control group (3·9 (sem 0·2)), but increased in the FO group (6·3 (sem 0·3); P< 0·01). The mean HR during supine resting conditions (control 56 (sem 10); FO 59 (sem 9)) was not affected by FO supplementation. Poincaré analysis of HR variability at rest exhibited a decreasing trend in parasympathetic activity in the FO group (SD1 (standard deviation of points perpendicular to the axis of line of identity)/SD2 (standard deviation of points along the axis of line of identity): control 0·02 (sem 0·01); FO − 0·05 (sem 0·02); P= 0·18). Peak HR was not affected by supplementation. However, during submaximal exercise over 5 min, fewer total heart beats were recorded in the FO group ( − 22 (sem 6) ( = − 4·5 beats/min)), but not in the control group (+1 (sem 4)) (P< 0·05). Supine HR recovery (half-time) after cycling was significantly faster after FO supplementation (control − 0·4 (sem 1·2) s; FO − 8·0 (sem 1·7) s; P< 0·05). A low intake of FO increased the omega-3 index and reduced the mean exercise HR and improved HR recovery without compromising the peak HR. A direct influence of DHA via reductions in the cardiac intrinsic beat rate was balanced by a reciprocal decrease in vagal tone.

Eicosapentaenoic acid and docosahexaenoic acid in whole blood are differentially and sex-specifically associated with cardiometabolic risk markers in 8-11-year-old danish children

n-3 long-chain polyunsaturated fatty acids improve cardiovascular risk markers in adults. These effects may differ between eicosapentaenoic acid (EPA, 20∶5n-3) and docosahexaenoic acid (DHA, 22∶6n-3), but we lack evidence in children. Using baseline data from the OPUS School Meal Study we 1) investigated associations between EPA and DHA in whole blood and early cardiometabolic risk markers in 713 children aged 8-11 years and 2) explored potential mediation through waist circumference and physical activity and potential dietary confounding. We collected data on parental education, pubertal stage, 7-day dietary records, physical activity by accelerometry and measured anthropometry, blood pressure, and heart rate. Blood samples were analyzed for whole blood fatty acid composition, cholesterols, triacylglycerol, insulin resistance by the homeostatic model of assessment (HOMA-IR), and inflammatory markers. Whole blood EPA was associated with a 2.7 mmHg (95% CI 0.4; 5.1) higher diastolic blood pressure per weight% EPA, but only in boys. Heart rate was negatively associated with both EPA and DHA status (P = 0.02 and P = 0.002, respectively). Whole blood EPA was negatively associated with triacylglycerol (P = 0.003) and positively with total cholesterol, low density and high density lipoprotein (HDL) cholesterol and HDL:triacylglycerol (all P<0.01) whereas DHA was negatively associated with insulin and HOMA-IR (P = 0.003) and tended to be negatively associated with a metabolic syndrome-score (P = 0.05). Adjustment for waist circumference and physical activity did not change the associations. The association between DHA and HOMA-IR was attenuated but remained after adjustment for fiber intake and none of the other associations were confounded by dietary fat, protein, fiber or energy intake. This study showed that EPA status was negatively associated with triacylglycerol and positively with cholesterols whereas DHA was negatively associated with insulin resistance, and both were inversely associated with heart rate in children. The sex-specific associations with blood pressure confirm our previous findings and warrant further investigation.

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.