Barbara J. Meyer

Dietary intakes and food sources of Omega-6 and Omega-3 polyunsaturated fatty acids.

Both n−6 and n−3 polyunsaturated fatty acids (PUFA) are recognized as essential nutrients in the human diet, yet reliable data on population intakes are limited. The aim of the present study was to ascertain the dietary intakes and food sources of individual n−6 and n−3 PUFA in the Australian population. An existing database with fatty acid composition data on 1690 foods was updated with newly validated data on 150 foods to estimate the fatty acid content of foods recorded as eaten by 10,851 adults in the 1995 Australian National Nutrition Survey. Average daily intakes of linoleic (LA), arachidonic (AA), α-linolenic (LNA), eicosapentaenoic (EPA), docosapentaenoic (DPA), and docosahexaenoic (DHA) acids were 10.8, 0.052, 1.17, 0.056, 0.026, and 0.106 g, respectively, with longchain (LC) n−3 PUFA (addition of FPA, DPA, and DHA) totaling 0.189 g; median intakes were considerably lower (9.0 g LA, 0.024 g AA, 0.95 g LNA, 0.008 g EPA, 0.006 g DPA, 0.015 g DHA, and 0.029 g LC n−3 PUFA). Fats and oils, meat and poultry, cereal-based products and cereals, vegetables, and nuts and seeds were important sources of n−6 PUFA, while cereal-based products, fats and oils, meat and poultry, cereals, milk products, and vegetable products were sources of LNA. As expected, seafood was the main source of LC n−3 PUFA, contributing 71%, while meat and eggs contributed 20 and 6%, respectively. The results indicate that the majority of Australians are failing to meet intake recommendations for LC n−3 PUFA (>0.2 g per day) and emphasize the need for strategies, to increase the availability and consumption of n−3-containing foods.

Effects of dietary saturated, monounsaturated and n-3 fatty acids on fasting lipoproteins, LDL size and post-prandial lipid metabolism in healthy subjects.

BACKGROUND The influence of the quality of dietary fat on some aspects of lipid metabolism-i.e. lipoprotein concentrations, post-prandial lipids and LDL size-is not completely understood, especially in healthy individuals. OBJECTIVES Aim of this study was to evaluate the effects of different types of dietary fat (monounsaturated vs. saturated fatty acids, and n-3 or placebo supplementation) on fasting lipoproteins, LDL size and post-prandial lipids in healthy people. DESIGN One hundred and sixty-two individuals were randomly assigned to follow two isoenergetic diets, one rich in saturated fatty acids (SFA diet) and the other in monounsaturated fatty acids (MUFA diet). Each group was further randomised to receive supplementation with fish oil (3.6 g/day) or placebo. RESULTS The type of diet significantly affected LDL cholesterol and triacylglycerol content, which was higher with the SFA diet and lower with the MUFA diet. The changes between the two diets were statistically significant for cholesterol (P<0.01) and triacylglycerol (P<0.03). VLDL cholesterol and triacylglycerol were significantly reduced and LDL cholesterol significantly increased by fish oil supplementation. Plasma triacylglycerol was significantly lower in those taking n-3 fatty acids, also 1 and 3 h after a test-meal. Neither type of diet nor n-3 supplementation affected LDL size. CONCLUSIONS A moderate substitution of saturated fatty acids with monounsaturated fatty acids has beneficial effects on lipid metabolism also in healthy individuals. A moderate supplementation of long-chain n-3 fatty acids in healthy individuals reduces both fasting and post-prandial triacylglycerol concentrations but increases LDL cholesterol, irrespective of the type of diet.

Fish oil supplementation in the treatment of major depression: A randomised double-blind placebo-controlled trial

Dietary deficiencies in essential omega-3 polyunsaturated fatty acids derived from fish are associated with depression and some fish oils may have therapeutic benefits. We aimed to determine whether taking tuna fish oil confers any additional benefit to conventional outpatient treatment for major depression. A randomized double-blind placebo-controlled four-month trial comparing tuna fish oil versus placebo was conducted on 83 outpatients with major depression. Despite large reductions in depression there were no significant differences at any assessment time point between patients receiving fish oil compared to placebo. Red blood cell incorporation of fatty acids indicated good compliance with oil supplementation, although this sample was not initially deficient in omega-3s. This particular dose and type of fish oil conferred no additional benefit to conventional treatment of depression in this sample. Future studies could target participants with pre-existing omega-3 deficiency and appraise alternate enriched types and higher doses of omega-3 supplementation.

Nutritional modulation of cognitive function and mental health

The important role of diet in cardiometabolic health is generally well recognised; for mental health, it is not so well understood. However, lifestyle risk factors for poor physical health are the same risk factors for mental illness, including poor diet. This is reflected by the high level of poor physical health in people with mental illness. Mediterranean, whole food diets have been associated with reduced risk for chronic disease, but very little research has investigated their mental health benefits. We provide a model for the pathways by which food components provided by a Mediterranean-style diet can facilitate healthy brain function. We then review evidence for the role of selected nutrients/food components - antioxidants, omega-3 fatty acids and B vitamins - in the brain and, hence, modulation of cognitive function and mental health. Converging evidence indicates multiple pathways by which these nutrients can assist in brain function, drawing from studies investigating them in isolation. There is very little work done on synergistic actions of nutrients and whole diets, highlighting a need for human intervention studies investigating benefits of Mediterranean-style diets for mental, as well as cardiometabolic health.

Impact of foods enriched with n-3 long-chain polyunsaturated fatty acids on erythrocyte n-3 levels and cardiovascular risk factors

Consumption of fish or fish oils rich in the n-3 long chain PUFA EPA and DHA may improve multiple risk factors for CVD. The objective of this study was to determine whether regular consumption of foods enriched with n-3 long-chain PUFA can improve n-3 long-chain PUFA status (erythrocytes) and cardiovascular health. Overweight volunteers with high levels of triacylglycerols (TG; >1.6 mmol/l) were enrolled in a 6-month dietary intervention trial conducted in Adelaide (n 47) and Perth (n 39), and randomised to consume control foods or n-3-enriched foods to achieve an EPA + DHA intake of 1 g/d. Test foods were substituted for equivalent foods in their regular diet. Erythrocyte fatty acids, plasma TG and other CVD risk factors were monitored at 0, 3 and 6 months. There were no significant differences between groups for blood pressure, arterial compliance, glucose, insulin, lipids, C-reactive protein (CRP) or urinary 11-dehydro-thromboxane B2 (TXB2) over 6 months, even though regular consumption of n-3-enriched foods increased EPA + DHA intake from 0.2 to 1.0 g/d. However, the n-3 long-chain PUFA content of erythrocytes increased by 35 and 53 % at 3 and 6 months, respectively, in subjects consuming the n-3-enriched foods. These increases were positively associated with measures of arterial compliance and negatively associated with serum CRP and urinary 11-dehydro-TXB2 excretion. Sustainable increases in dietary intakes and erythrocyte levels of n-3 long-chain PUFA can be achieved through regular consumption of suitably enriched processed foods. Such increases may be associated with reduced CV risk.

Australian Food Sources and Intakes of Omega–6 and Omega–3 Polyunsaturated Fatty Acids

Background/Aims: Both ω–6 and ω–3 polyunsaturated fatty acids (PUFAs) are recognised as essential nutrients in the human diet, yet we have little information on the extent to which different food sources contribute to their intake. The aim of the present study was to ascertain the daily intakes and food sources of ω–6 and ω–3 PUFAs in our local community. Methods: Three-day food records were obtained from 83 healthy adults living in the Illawarra region of New South Wales. The PUFA composition of the foods which they consumed was derived from food composition tables and recently published food analysis data. Results: Polyunsaturated margarine, nuts/seeds, bread, snacks/desserts and takeaway foods were important sources of ω–6 PUFAs, while canola oil and margarine, takeaway foods, snacks/desserts and bread were sources of α-linolenic acid (LNA), an ω–3 PUFA. As expected, fish was the main source of the very long chain (VLC) ω–3 PUFAs, i.e. eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA), to which significant health benefits are attributed. An unexpected finding, however, was that, due to the large amount eaten, meat was also a major contributor (29%) to the dietary intake of VLC ω–3 PUFAs. Median intakes of ω–6 and ω–3 PUFAs were 9.9 and 1.2 g/day, respectively, resulting in a dietary ω–6:ω–3 ratio of 8:1. The median intake of VLC ω–3 PUFA was 0.18 g/day. Conclusion: We have identified food sources and intakes of PUFAs for an Australian subpopulation differentiating between ω–6 and ω–3 PUFAs. Whilst canola and fish were the primary sources of LNA and VLC ω–3 PUFAs respectively, we found that meat made a significant contribution to VLC ω–3 PUFA intake.

Limited Lipid-lowering effects of regular consumption of whole soybean foods

Aim: To examine cardiovascular health benefits of foods containing a whole soybean extract. Methods: The study design was a randomized, placebo-controlled crossover trial of consuming soy-based milk and yoghurt (treatment) or equivalent dairy products (control) for 5 weeks each. Twenty-six mildly hypercholesterolaemic and/or hypertensive volunteers were recruited from the community as study volunteers, of which 23 completed. Main outcome measures included clinic and ambulatory blood pressure, arterial compliance, lipids, fatty acids and isoflavones in fasted blood and 24-hour urinary isoflavone excretion. Nutrient intakes were assessed initially and after each 5-week period. Multiple regression analyses were used to determine predictor variables in statistical models; order effects were tested by repeated measures ANOVA. Changes in Lp(a) were determined by Wilcoxon signed ranks tests; other differences between treatment and control were assessed by t tests. Results: Plasma and urinary isoflavones were markedly increased by whole soy supplementation but there were no overall differences in plasma lipids, blood pressure or arterial compliance between the soy and dairy diets. However, in 8 equol-positive subjects (equol detected in either plasma or urine), retrospective analysis revealed significant reductions in total cholesterol (8.5%), LDL cholesterol (10%), LDL:HDL ratio (13.5%), plasma triglycerides (21%) and lipoprotein(a) (11%) with the soy diet. These reductions were independent of changes in polyunsaturated fat and other macronutrient intakes. Conclusions: Regular consumption of whole soybean milk and yogurt products had no effect on plasma lipids, blood pressure or arterial compliance in at-risk subjects, despite substantially increasing isoflavone levels in blood and urine. Retrospective analysis suggests that improvement of plasma lipids may have been limited to equol-positive subjects.

Biomarker validation of a long-chain omega-3 polyunsaturated fatty acid food frequency questionnaire

Long-chain omega-3 PUFA (LC n−3 PUFA) are beneficial for health. To date there is no specific food frequency questionnaire (FFQ) to assess LC n−3 PUFA intakes. The objective of this study is to validate our newly developed FFQ by comparison with LC n−3 PUFA content of both red blood cells (RBC) and plasma, expressed as a percentage of total FA. Fifty-three healthy male and female subjects were recruited from Wollongong, Australia. Average LC n−3 PUFA intakes (mg/d) were estimated using the new FFQ. RBC and plasma FA were assessed using GC. Spearman correlation coefficients were used to assess the linear relationship between FFQ intakes and both RBC and plasma FA. The results show that there were significant Spearmans correlation coefficients between the FFQ intakes and RBC (and plasma) FA for total LC n−3 PUFA, EPA, and DHA (0.50 (0.54), 0.39 (0.54) and 0.40 (0.48), respectively) but not for docosapentaenoic acid. The FFQ was also an effective ranking tool. The FFQ is a valid method based on erythrocyte and plasma FA as biochemical markers. In conclusion, the new FFQ is a valid method that can be used to estimate the LC n−3 PUFA intake of adults.

Validation of an Australian electronic food frequency questionnaire to measure polyunsaturated fatty acid intake

OBJECTIVE To develop and validate a simple non-invasive method that estimates the intakes of omega-3 and omega-6 polyunsaturated fatty acids (PUFA) in a healthy adult population. METHODS A new electronic PUFA food frequency questionnaire (FFQ) was validated by comparison with a 3-d weighed food record and blood biomarkers (erythrocytes and plasma) using the method of triads model and tested for reproducibility. Healthy subjects were recruited from the local Illawarra Region, New South Wales, Australia. RESULTS The PUFA FFQ adequately estimated intakes for eicosapentaenoic acid, docosahexaenoic acid, total long chain omega-3 PUFA, linoleic acid, total omega-6 PUFA, and total PUFA, which were comparable with results from the 3-d food record. Eicosapentaenoic acid, docosahexaenoic acid, and total long chain omega-3 showed high validity coefficients for erythrocytes (and plasma) 0.92 (0.87), 0.69 (0.64), and 0.78 (0.73) (P < 0.05), respectively. Spearmans rank correlation coefficients ranged from 0.48 to 0.76 when the PUFA FFQ was tested for reproducibility (P < 0.05). CONCLUSION The electronic PUFA questionnaire was found to be reproducible and is a valid tool to assess PUFA intakes in a healthy adult population.

Dietary intake of fish and PUFA, and clinical depressive and anxiety disorders in women.

Fish and PUFA consumption are thought to play a role in mental health; however, many studies do not take into account multiple sources of PUFA. The present study analysed data from a sample of 935 randomly selected, population-based women aged 20–93 years. A validated and comprehensive dietary questionnaire ascertained the consumption of n-3 and n-6 PUFA. Another assessed fish and energy intake and provided data for a dietary quality score. The General Health Questionnaire-12 (GHQ-12) measured psychological symptoms and a clinical interview (Structured Clinical Interview for DSM-IV-TR Research Version, Non-patient edition) assessed depressive and anxiety disorders. Median dietary intakes of long-chain n-3 fatty acids (310 mg/d) were below suggested dietary target levels. The only PUFA related to categorical depressive and anxiety disorders was DHA. There was a non-linear relationship between DHA intake and depression; those in the second tertile of DHA intake were nearly 70% less likely to report a current depressive disorder compared to those in the first tertile. The relationship of DHA to anxiety disorders was linear; for those in the highest tertile of DHA intake, the odds for anxiety disorders were reduced by nearly 50% after adjustments, including adjustment for diet quality scores, compared to the lowest tertile. Those who ate fish less than once per week had higher GHQ-12 scores, and this relationship was particularly obvious in smokers. These are the first observational data to indicate a role for DHA in anxiety disorders, but suggest that the relationship between DHA and depressive disorders may be non-linear.