Fatty fish intake,n‐3 fatty acids and self‐rated health in middle‐aged adults

Background – Since n‐3 fatty acids, abundant in fatty fish, may improve health, we raised the question whether self‐reported intake frequency of fatty fish (FF) might be related to the percentage of n‐3 fatty acids in serum phospholipids (PL‐n‐3), and also to self‐rated health (H). Design – The study followed a cross‐sectional design. Methods – In the cross‐sectional Oslo Health Study, PL‐n‐3 were determined in 121 middle‐aged ethnic Norwegians and 102 immigrants from the Indian subcontinent and correlated with FF and H. Logistic regression was used to study the relationship between PL‐n‐3 and H (dichotomized, i.e. Poor vs. Good health). Results – FF correlated positively with PL20:5n‐3 (PL‐EPA, r = 0.467, p <0.001) and PL22:6n‐3 (PL‐DHA, r = 0.499, p <0.001), and negatively with PL20:4n‐6 (PL‐AA, r = –0.350, p = 0.001). H was positively associated with PL‐EPA (r = 0.321, p <0.001) and PL‐DHA (r = 0.275; p <0.001), but negatively with PL‐AA (r = –0.220, p = 0.001). The odds ratio for reporting Poor vs. Good health was significantly higher in subjects with low levels of PL‐EPA (OR = 1.49; 95% confidence interval = 1.17–1.89, p = 0.001), persisting after adjusting for sex, physical activity, ethnicity and length of education. Conclusion – The intake frequency of fatty fish is related to n‐3 fatty acids in the serum phospholipids, and to self‐rated health.     

Lipase/acyltransferase‐catalysed interesterification of fat blends containing n‐3 polyunsaturated fatty acids

The lipase/acyltransferase from Candida parapsilosis is an original biocatalyst that preferentially catalyses alcoholysis over hydrolysis in biphasic aqueous/organic media. In this study, the performance of the immobilised biocatalyst in the interesterification in solvent‐free media of fat blends rich in n‐3 polyunsaturated fatty acids (n‐3 PUFA) was investigated. The interesterification activity of this biocatalyst at a water activity (a_w) of 0.97 was similar to that of commercial immobilised lipases at a_w values lower than 0.5. Thus, the biocatalyst was further used at an a_w of 0.97. Response surface modelling of interesterification was carried out as a function of medium formulation, reaction temperature (55–75 °C) and time (30–120 min). Reaction media were blends of palm stearin (PS), palm kernel oil and triacylglycerols (TAG) rich in n‐3 PUFA (“EPAX 4510TG”; EPAX AS, Norway). The best results in terms of decrease in solid fat content were observed for longer reaction time (>80 min), lower temperature (55–65 °C), higher “EPAX 4510TG” content and lower PS concentration. Reactions at higher temperature led to final interesterified fat blends with lower free fatty acid contents. TAG with high equivalent carbon number (ECN) were consumed while acylglycerols of lower ECN were produced.     

Effect of phospholipid n‐3 polyunsaturated fatty acids on rat lipid metabolism

It has been demonstrated that the amount and type of dietary fat are factors involved in the risk of arteriosclerosis and coronary or cerebral artery disease through lipid metabolism. In this study, we investigated the effects of phospholipids (PLs) containing n‐3PUFAs on lipid metabolism in rats. PLs containing n‐3PUFAs were prepared from squid (Todarodes pacificus) mantle muscle. Groups of male Wistar rats were fed AIN93G diet containing soybean oil (SO, 7%), fish oil (1.2%) + SO (5.8%), soybean PLs (1.8%) + SO (5.2%), or PLs containing n‐3PUFAs (1.8%) + SO (5.2%). The following indicators were assayed as indexes of lipid metabolism: TAG and cholesterol in serum and liver, fecal cholesterol, bile‐acid excretion, and liver mRNA expression levels of genes encoding proteins involved in cholesterol homeostasis. Serum and liver TAG contents decreased significantly in the group fed PLs containing n‐3PUFAs as compared to other groups, accompanied by a significant decline in the expression level of sterol regulatory element binding protein‐1c. The decrease in cholesterol content in the group fed PLs containing n‐3PUFAs was due to the increase in fecal cholesterol excretion and the increase of mRNA expression levels of ATP‐binding cassette (ABC) G5 and ABCG8 in liver. Practical applications : PLs containing n‐3PUFAs decreased serum and liver TAG contents compared with that induced by soybean PLs. Further, PLs containing n‐3PUFAs can induce a reduction in serum and liver cholesterol concentrations as well as the triglyceride‐reducing effect of conventional n‐3PUFAs containing TAG. In other words, dietary n‐3PUFAs contained in PLs can prevent life‐style diseases such as hyperlipidemia, arteriosclerosis and coronary, or cerebral artery disease more effectively than TAG containing n‐3PUFAs. Therefore, it is expected that the risk of lifestyle diseases would be decreased if PL containing n‐3PUFAs can be supplied routinely. In this study, PLs containing n‐3PUFAs were prepared from squid mantle muscle. On an industrial scale, such PLs can be produced from various unused resources and waste materials of fisheries. We conclude that highly functional foods could be developed based on the findings of this study, and would be available for health promotion worldwide.     

Efficient stabilization of bulk fish oil rich in long‐chain polyunsaturated fatty acids

The aim of the present study was to systematically investigate the possibilities of stabilizing a bulk oil rich in long‐chain polyunsaturated fatty acids under ambient conditions. Combinations of different antioxidants (α‐, γ‐ and/or δ‐tocopherol, rosmarinic acid and rosemary extract rich in carnosic acid) as well as lecithin and citric acid were systematically investigated. Efficient stabilization was achieved by choosing a combination of tocopherols rich in γ‐ or δ‐tocopherol and low in α‐tocopherol, by including tocopherol‐sparing synergists like ascorbyl palmitate and carnosic acid from rosemary extract and metal‐chelating agents. For carnosic acid, a concentration of 400 mg/kg oil provides sufficient protection; the concentration of the metal chelator should be adapted to the concentration of metal ions present in the oil. As an alternative ingredient with metal‐chelating and tocopherol‐sparing activity, lecithin may be included in the formulation, but its poor solubility in bulk oils limits its use.     

Synthesis of regioisomerically pure triacylglycerols containing n‐3 very long‐chain polyunsaturated fatty acids

There is growing scientific evidence that consumption of n‐3 very long‐chain polyunsaturated fatty acids (n‐3 VLC‐PUFA) helps in brain and eye development, and protects against a range of common degenerative diseases. This has provided the impetus to the scientists to develop new and renewable sources for these important fatty acids so that the food industry is able to produce and market products fortified with n‐3 VLC‐PUFA. The bioactive efficacy and stability of food products containing n‐3 VLC‐PUFA may be determined not only by the amount of n‐3 VLC‐PUFA present but also by the positional distribution of these acids within the triacylglycerol (TAG) molecules (regiopurity). Studies of the effects of positional distribution on the functionality of n‐3 VLC‐PUFA containing oils have been hampered by a general lack of pure TAG regioisomers for experimentation. This paper reviews methods that have been used for the synthesis of TAG regioisomers containing n‐3 VLC‐PUFA, with special reference to those in which one n‐3 VLC‐PUFA occurs in combination with two long‐chain saturated acids.     

Searching for health beneficial n‐3 and n‐6 fatty acids in plant seeds

Various plant seeds have received little attention in fatty acid research. Seeds from 30 species mainly of Boraginaceae and Primulaceae were analysed in order to identify potential new sources of the n‐3 PUFA α‐linolenic acid (ALA) and stearidonic acid (SDA) and of the n‐6 PUFA γ‐linolenic acid (GLA). The fatty acid distribution differed enormously between genera of the same family. Echium species (Boraginaceae) contained the highest amount of total n‐3 PUFA (47.1%), predominantly ALA (36.6%) and SDA (10.5%) combined with high GLA (10.2%). Further species of Boraginaceae rich in both SDA and GLA were Omphalodes linifolia (8.4, 17.2%, resp.), Cerinthe minor (7.5, 9.9%, resp.) and Buglossoides purpureocaerulea (6.1, 16.6%, resp.). Alkanna species belonging to Boraginaceae had comparable amounts of ALA (37.3%) and GLA (11.4%) like Echium but lower SDA contents (3.7%). Different genera of Primulaceae (Dodecatheon and Primula) had varying ALA (14.8, 28.8%, resp.) and GLA portions (4.1, 1.5%, resp.), but similar amounts of SDA (4.9, 4.5%, resp.). Cannabis sativa cultivars (Cannabaceae) were rich in linoleic acid (57.1%), but poor in SDA and GLA (0.8, 2.7%, resp.). In conclusion, several of the presented plant seeds contain considerable amounts of n‐3 PUFA and GLA, which could be relevant for nutritional purposes due to their biological function as precursors for eicosanoid synthesis. Practical applications: N‐3 PUFA are important for human health and nutrition. Unfortunately, due to the increasing world population, overfishing of the seas and generally low amounts of n‐3 PUFA in major oil crops, there is a demand for new sources of n‐3 PUFA. One approach involves searching for potential vegetable sources of n‐3 PUFA; especially those rich in ALA and SDA. The conversion of ALA to SDA in humans is dependent on the rate‐limiting Δ6‐desaturation. Plant‐derived SDA is therefore a promising precursor regarding the endogenous synthesis of n‐3 long‐chain PUFA in humans. The present study shows that, in addition to seed oil of Echium, other species of Boraginaceae (Cerinthe, Omphalodes, Lithospermum, Buglossoides) and Primulaceae (Dodecatheon, Primula), generally high in n‐3 PUFA (30–50%), contain considerable amounts of SDA (5–10%). Therefore, these seed oils could be important for nutrition.     

Effects of n‐3 polyunsaturated fatty acids on endothelial function

Dysfunction of the vascular endothelium is an early event in the development of cardiovascular disease and methods are now available to measure endothelial function in vivo in man. Endothelial function may have advantages as an endpoint in human nutrition intervention trials over cardiovascular risk factors. Several studies have now been published on effects of the n‐3 polyunsaturated fatty acids on endothelial function. When ingested together, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have favourable effects on vasodilation in coronary arteries, brachial arteries and the skin microcirculation. However, published studies do not agree on the effects of EPA and DHA when ingested separately. Further research is needed to resolve these disagreements and extend these observations particularly at intakes of EPA and DHA which are achievable by diet.     

Lipase selectivity toward fatty acids commonly found in fish oil

The main objective of this study was to compare the fatty acid selectivity of numerous commercially available lipases toward the most ubiquitous fatty acids present in fish oils in form of their corresponding ethyl esters. Special interest was taken in their ability to separate the n‐3 long‐chain polyunsaturated fatty acids (PUFA), mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), from the more saturated fatty acids as well as exploiting the putative discrimination between these highly valuable n‐3 PUFA. Hydrolysis of sardine oil ethyl esters in a Tris buffer solution by 12 microbial lipases is described. The results reveal that all of the lipases strongly discriminate against the n‐3 PUFA and prefer the more saturated fatty acids as substrates. Most of the lipases discriminate between EPA and DHA in favor of EPA, however, 2 bacterial lipases from Pseudomonas were observed to prefer DHA to EPA. Digestive lipolytic enzymes isolated from salmon and rainbow trout intestines displayed reversed fatty acid selectivity when their fish oil triacylglycerol hydrolysis was studied. Thus, the n‐3 PUFA including EPA and DHA were observed to be hydrolyzed at a considerably higher rate than the more saturated fatty acids.     

Thermal degradation of long‐chain polyunsaturated fatty acids during deodorization of fish oil

Long‐chain polyunsaturated fatty acids (LC‐PUFA) of the n‐3 series, particularly eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid, have specific activities especially in the functionality of the central nervous system. Due to the occurrence of numerous methylene‐interrupted ethylenic double bonds, these fatty acids are very sensitive to air (oxygen) and temperature. Non‐volatile degradation products, which include polymers, cyclic fatty acid monomers (CFAM) and geometrical isomers of EPA and DHA, were evaluated in fish oil samples obtained by deodorization under vacuum of semi‐refined fish oil at 180, 220 and 250 °C. Polymers are the major degradation products generated at high deodorization temperatures, with 19.5% oligomers being formed in oil deodorized at 250 °C. A significant amount of CFAM was produced during deodorization at temperatures above or equal to 220 °C. In fact, 23.9 and 66.3 mg/g of C20 and C22 CFAM were found in samples deodorized at 220 and 250 °C, respectively. Only minor changes were observed in the EPA and DHA trans isomer content and composition after deodorization at 180 °C. At this temperature, the formation of polar compounds and CFAM was also low. However, the oil deodorized at 220 and 250 °C contained 4.2% and 7.6% geometrical isomers, respectively. Even after a deodorization at 250 °C, the majority of geometrical isomers were mono‐ and di‐trans. These results indicate that deodorization of fish oils should be conducted at a maximal temperature of 180 °C. This temperature seems to be lower than the activation energy required for polymerization (intra and inter) and geometrical isomerization.     

The production of n‐3 long‐chain polyunsaturated fatty acids in transgenic plants

Long‐chain polyunsaturated fatty acids (LC‐PUFA) now have a proven role in human health and nutrition, including the n‐3 forms normally found in fish oils. Unfortunately, global fish stocks are now more than ever subject to over‐fishing and environmental pollution, indicating the need for an alternative source of fish oils. Recent efforts have focussed on the production of LC‐PUFA in transgenic plants to provide a sustainable and clean source of fish oils. The current progress in this area is considered, as well as the bottlenecks that remain to be overcome.     

θ3 fatty acids in freshwater fish from south brazil

Lipid and fatty acid levels in the edible flesh of 17 freshwater fish from Brazil’s southern region were determined. Analyses of fatty acid methyl esters were performed by gas chromatography. Palmitic acid (C_16:0) was the predominant saturated fatty acid, accounting for 50–70% of total saturated acids. Oleic acid (C_18:1θ9) was the most abundant monounsaturated fatty acid. Linoleic acid (C_18:2θ6), linolenic acid (C_18:3θ3), and docosahexaenoic acid (C_22:6θ3) were the predominant polyunsaturated fatty acids (PUFA). The data revealed that species such as truta, barbado, and corvina were good sources of eicosapentaenoic acid (C_20:5θ3) and docosahexaenoic acid (C_22:6θ3), and that most freshwater fish examined were good sources of PUFA θ3.     

Modelling lipase‐catalysed transesterification of fats containing n‐3 fatty acids monitored by their solid fat content

Transesterification of fat blends rich in n‐3 polyunsaturated fatty acids (n‐3 PUFA), catalysed by a commercial immobilised thermostable lipase from Thermomyces lanuginosa, was carried out batch‐wise. Experiments were performed, following central composite rotatable designs (CCRDs) as a function of reaction time, temperature and media formulation. Mixtures of palm stearin, palm kernel oil and a commercial concentrate of triacylglycerols rich in n‐3 PUFA (“EPAX 2050TG” in CCRD‐1 and “EPAX 4510TG” in CCRD‐2) were used. The time‐course of transesterification was indirectly followed by the solid fat content (SFC) values of the blend at 10 °C, 20 °C, 30 °C and 35 °C. A decrease in all SFC values of the blends at 10 °C, 20 °C, 30 °C and 35°C was observed upon transesterification. The SFC_{10 °C} and SFC_{20 °C} of transesterified blends varied between 18 and 48 and SFC_{35 °C} between 6 and 24. These values fulfil the technological requirements for the production of margarines. Under our conditions, lipid oxidation may be neglected. However, the accumulation up to 8.3% free fatty acids in reaction media is a problem to overcome. The development of response surface models, describing both the final SFC value and the SFC decrease, will allow predicting results for novel proportions of fats and oils and/or a novel combination time‐temperature.     

Oil content and fatty acid composition of commercially important Turkish fish species

The oil content and fatty acid composition of commercially important Turkish fish species (anchovy,Engraulis encrasicholus; freshwater rainbow trout,Salmo gairdneri; and cultured salmon,S. salar) were determined. Palmitic (16∶0), palmitoleic (16∶1), oleic (18∶1), and docosahexaenoic (22∶6) acids were the most abundant fatty acids in all species. Eicosapentaenoic acid (20∶5) was twice as high in the anchovy oil as in the rainbow trout and salmon oils. Significant quantities of linoleic acid (18∶2) and docosahexaenoic acids (22∶6) were found in both rainbow trout and salmon samples. The individual fatty acid data obtained from rainbow trout and salmon were similar to each other. All three fish species contain high levels of n-3 polyunsaturated fatty acids and would be suitable for inclusion in the formulation of low-fat highly unsaturated diets.     

α‐Linolenic acid metabolism in adult humans: the effects of gender and age on conversion to longer‐chain polyunsaturated fatty acids

This review summarises and evaluates current knowledge of α‐linolenic acid (αLNA) metabolism in adult humans. The principal biological role of αLNA appears to be as a precursor for the synthesis of longer‐chain n‐3 polyunsaturated fatty acids (PUFA). Stable isotope tracer studies indicate that conversion of αLNA to eicosapentaenoic acid (EPA) occurs but is limited in men and that further transformation to docosahexaenoic acid (DHA) is very low. A lower proportion of αLNA is used for β‐oxidation in women compared with men, while the fractional conversion to the longer‐chain n‐3 PUFA is greater, possibly due to the regulatory effects of oestrogen. Increasing αLNA intake for a period of weeks results in an increase in the proportion of EPA in plasma lipids, circulating cells and breast milk, but there is no increase in DHA, which may even decline in some pools at high αLNA intakes. Overall, αLNA appears to be a limited source of longer‐chain n‐3 PUFA in man, and so adequate intakes of preformed long‐chain n‐3 PUFA, in particular DHA, may be important for maintaining optimal tissue function. The capacity to up‐regulate αLNA transformation in women may be important for meeting the demands of the foetus and neonate for DHA.     

Confusion over different types of n‐3 polyunsaturated fatty acids

There are two kinds of n‐3 polyunsaturated fatty acid (PUFA). Alpha‐linolenic acid (ALA) is the parent n‐3 PUFA; it cannot be synthesized by the human body and as a result is an essential fatty acid. The two long chain n‐3 PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) can in principle be synthesized from ALA or obtained from the diet. While the cardioprotective effects of long chain n‐3 PUFA are well established the effects of ALA on the cardiovascular system are more controversial. The Lyon Diet Heart Study which it is claimed provides evidence for beneficial effects of ALA on the cardiovascular system is flawed. The argument that ALA conversion into EPA and DHA provides significant quantities of the two long chain n‐3 PUFA is unsustainable as rates of conversion are too low. To avoid confusion a distinction needs to be drawn between ALA and the long chain n‐3 PUFA. Health claims for foods rich in EPA and DHA cannot be extended to foods rich in ALA nor is ALA a substitute for EPA and DHA in vegetarian diets.     

Effects of milk fat replacement by PUFA enriched fats on n‐3 fatty acids,conjugated dienes and volatile compounds of fermented milks

A study was carried out to determine the profiles of fatty acids in fermented milks and dairy derivatives made with milk fat substituted by polyunsaturated fatty acid (PUFA)‐enriched fat. In order to improve the organoleptic properties of those products, whey protein concentrates (WPC) were added during the manufacturing process. Interest was focused during manufacturing and storage period on the contents of “healthy” fatty acids, mainly conjugated linoleic acid and n‐3 PUFA. Contents of these fatty acids were not affected by the manufacture practices and neither did addition of WPC during manufacturing nor cold storage cause their decrease. Percentages of total n‐3 fatty acids in fat from dairy derivatives enriched in PUFA after 21 d of storage (1.45%) were very close to those obtained before processing (1.39%). Contents did not differ either substantially when WPC were added during manufacturing (1.46%). The increase of volatile compounds was also examined. Although a slight decrease in the total volatile content was observed, percentages of different compounds were not modified when milk fat was substituted by PUFA enriched fat.     

Processed animal products with emphasis on polyunsaturated fatty acid content

The fat composition of processed fish and meat varies due to the source of the animal diet and to the fats used during processing. The aim of this study was to analyse the fatty acid profiles in some commonly available fish and meat fast foods. Variation between similar products from different brands indicated the use of different fat sources during processing. Especially in fish products, a high variation was found in the n‐6/n‐3 ratio, being up to more than 400‐fold higher than in plain fish, which might be of special concern in the evaluation of diet‐related health claims. Many products showed considerable differences compared to those included in the official database used for calculation of dietary intake. This leads to the conclusion that the fat sources used during processing of fast food should be reported and available to the consumers. I nterdisciplinary dialogue between all sectors involved in food production, processing and health care is proposed to evaluate optimal development of fast foods with nutritionally favourable fat composition.