Aktuelle Beurteilung ernährungswissenschaftlicher Aspekte der Linolensäuren

Current Views of Nutritional Aspects of Linolenic Acids The linolenic (n-3) type of fatty acid has many metabolic and chemical properties similar to those of the linoleic (n-6) type. Activation to CoA esters and esterification to lipids occurs relatively independent of the n-3 or n-6 structure. Both types of dietary polyunsaturated fatty acid appear able to reduce serum cholesterol levels and diminish some risk factors associated with cardiovascular disease. Nevertheless, the presence of the added terminal double bond in the n-3 fatty acids diminishes their reactivity in physiological conditions with the cyclooxygenase enzyme that forms prostaglandins. Also the formation of leukotriene derivatives from 20:5n-3 appears decreased relative those from 20:4n-6. This lower reactivity of n-3 acids also is associated with a lower ability to relieve the symptoms of essential fatty acid deficiency in experimental animals. The n-6 acids are thus defined as the essential fatty acids that physiologically form the active eicosanoids. Because villagers traditionally ingesting maritime foods have decreased incidence of cardiovascular disease and thrombotic deaths, current attention is directed to the dietary balance of n-3 and n-6 fatty acids. Recent concepts of platelet function and dietary lipids in coronary thrombosis, vasospasm and angina (Herz 5, 34–41 [1980]) suggest that some dietary balance between the n-3 and n-6 polyunsaturated fatty acids may be beneficial in decreasing the development of coronary artery disease and thromboembolisms.     

Biological effects of fish oils in relation to chronic diseases

The low incidence of cardiovascular disease in Greenland Eskimos appears to be due to their high intake of seal, whale and fish. The lipids of these marine animals lower serum triglyceride and cholesterol levels and help to prevent blood clotting. The latter effect has been related to a change in the balance of prostacyclin and thromboxane as a result of replacing n-6 polyunsaturated fatty acids in the body by n-3 polyunsaturated fatty acids present in marine lipids. Dietary fish oils have also been shown to inhibit development of mammary, pancreatic, intestinal and prostatic tumors in experimental animals. This effect may likewise be due to changes in the production of prostaglandins or related compounds. The involvement of prostaglandins and leukotrienes in immune responses has led to studies on the effects of fish oil on various chronic diseases associated with abnormalities of the immune system. Some of these diseases, such as multiple sclerosis and psoriasis, are also relatively uncommon in Eskimos. Preliminary results of these studies are encouraging, but more work is required to assess the usefulness of dietary fish oils in treatment of these diseases. In addition to their apparent therapeutic value, n-3 fatty acids are considered essential dietary components since they cannot be synthesized in the body and appear necessary for normal vision and probably other body functions. Presented at the American Oil Chemists' Society short course on Marine Lipids and EPA held at the Sheraton Royal Waikaloa Hotel, Hawaii, May 1986.     

Lipids in chronic kidney disease: Alterations and interventions

Pharmacological and dietary approaches to reducing high blood lipids in the general population decrease cardiovascular disease risk. Patients with chronic kidney disease (CKD) often display elevated blood lipids, and reducing cholesterol levels with statin drugs reduces cardiovascular disease in patients with moderate CKD, similar to the effects in the general population. Benefits to kidney disease itself appear to be marginal, if present. Studies with omega‐3 fatty acids indicate that both cardiovascular and kidney disease progression may be slowed by dietary omega‐3 fatty acids in CKD patients, but long‐term studies are needed to confirm these findings.     

N-3 Polyunsaturated Fatty Acids: Relationship to Inflammation in Healthy Adults and Adults Exhibiting Features of Metabolic Syndrome

Individuals with metabolic syndrome (MetS) have a higher risk of type 2 diabetes and cardiovascular disease, therefore, research has been directed at reducing various components that contribute to MetS and associated metabolic impairments, including chronic low-grade inflammation. Epidemiological, human, animal and cell culture studies provide evidence that dietary n-3 polyunsaturated fatty acids (n-3 PUFA), including alpha-linolenic acid (18:3n-3, ALA), eicosapentaenoic acid (20:5n-3, EPA) and/or docosahexaenoic acid (22:6n-3, DHA) may improve some of the components associated with MetS. The current review will discuss recent evidence from human observational and intervention studies that focused on the effects of ALA, EPA or DHA on inflammatory markers in healthy adults and those with one or more features of MetS. Observational studies in healthy adults support the recommendation that a diet rich in n-3 fatty acids may play a role in preventing and reducing inflammation, whereas intervention studies in healthy adults have yielded inconsistent results. The majority of intervention studies in adults with features of MetS have reported a benefit for some inflammatory measures; however, other studies using high n-3 fatty acid doses and long supplementation periods have reported no effect. Overall, the data reviewed herein support recommendations for regular fatty fish consumption and point toward health benefits in terms of lowering inflammation in adults with one or more features of MetS.     

Role of n-3 Fatty Acids on Bile Acid Metabolism and Transport in Dyslipidemia: A Review

Dietary n-3 fatty acids, especially of marine origin, eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3), have always been lauded for their profound effects on regulating the risk factors for major metabolic disorders. Yet, their consumption rate is poor compared to n-6 fatty acids [linoleic acid (18:2n-6)], which are predominantly consumed. Hence, the skewed n-6 to n-3 fatty acid ratio may have a bearing on the risk factors of various diseases, including dyslipidemia. Dyslipidemia and other lifestyle diseases associated with it, such as diabetes, obesity, hypertension, are a growing concern in both developed and developing countries. A common strategy for addressing dyslipidemia involves bile acid (BA) sequestration, to interrupt the enterohepatic circulation of BA, resulting in the modulation of lipid absorption in the intestine, thereby normalizing the levels of circulating lipids. The BA homeostasis is under the tight control of hepatic and enteric BA transporters. Many investigations have reported the effects of dietary constituents, including certain fatty acids on the reabsorption and transport of BA. However, a critical review of the effects of n-3 fatty acids on BA metabolism and transport is not available. The present review attempts to explore certain unmapped facets of the n-3 fatty acids on BA metabolism and transport in dyslipidemia, and their interplay with biological processes involving lipid rafts and gut microbiome.     

Role of Lipids in the Onset,Progression and Treatment of Periodontal Disease. A Systematic Review of Studies in Humans

The risk of different oral problems (root caries, tooth mobility, and tooth loss) can be increased by the presence of periodontal disease, which has also been associated with a growing list of systemic diseases. The presence of some bacteria is the primary etiology of this disease; a susceptible host is also necessary for disease initiation. In this respect, the progression of periodontal disease and healing of the periodontal tissues can be modulated by nutritional status. To clarify the role of lipids in the establishment, progression, and/or treatment of this pathology, a systematic review was conducted of English-written literature in PubMed until May 2016, which included research on the relationship of these dietary components with the onset and progression of periodontal disease. According to publication type, randomized-controlled trials, cohort, case-control and cross-sectional studies were included. Among all the analyzed components, those that have any effect on oxidative stress and/or inflammation seem to be the most interesting according to current evidence. On one hand, there is quite a lot of information in favor of a positive role of n-3 fatty acids, due to their antioxidant and immunomodulatory effects. On the other hand, saturated fat-rich diets increase oxidative stress as well the as intensity and duration of inflammatory processes, so they must be avoided.     

Role of essential fatty acids in the function of the developing nervous system

The basis for n-3 fatty acid essentiality in humans includes not only biochemical evidence but functional measures associated with n-3 deficiency in human and nonhuman primates. Functional development of the retina and the occipital cortex are affected by α-linolenic acid deficiency and by a lack of docosahexaenoic acid (DHA) in preterm infant formulas and, as reported more recently, in term diets. Functional effects of n-3 supply on sleep-wake cycles and heart rate rhythms support the need for dietary n-3 fatty acids during early development. Our results indicate that n-3 long-chain polyunsaturated fatty acids should be considered provisionally essential for infant nutrition. DHA may also be required by individuals with inherited metabolic defects in elongation and desaturation activity, such as patients with peroxisomal disorders and some forms of retinitis pigmentosa.     

Die Fettsäuren in der Nahrung: Ihre Bedeutung für Serumlipide,Lipoproteine und Atherosklerose

Dietary Fatty Acids: their Impact on Serum Lipids, Lipoproteins and Atherosclerosis There are important new data concerning the influence of dietary fats on serum cholesterol and lipoproteins. Earlier results of US-American authors, expressed in the regression equations of Keys, of Hegsted and their collaborators, have been amply confirmed even by authors who interpret their results differently. More recent results concerning trans-fatty acids, stearic acid, n-3-fatty acids which are not considered in the formulae of Keys and Hegsted could have been predicted from modern biochemistry of fatty acids. There are new results describing the influence of chain length of fatty acids on serum lipids. Recent studies center around the influence of fatty acids on lipoproteins. It appears that n-6-polyenoic fatty acids lower LDL but n-3-polyenoic fatty acids lower VLDL. Within the range of foods, commercially available in central Europe, fatty acids do not influence HDL.     

Improved Extraction of Saturated Fatty Acids but not Omega-3 Fatty Acids from Sheep Red Blood Cells Using a One-Step Extraction Procedure

Several methods are available to extract total lipid and methylate fatty acids from a range of samples including red blood cells (RBC). Fatty acid analysis of human RBC can be undertaken using a two-step extraction and methylation or a combined one-step extraction and methylation procedure. The lipid composition of sheep RBC differs significantly from that of humans and may affect their extraction. The purpose of the current study was to examine the efficiency of extraction of lipid and detection of fatty acids from sheep RBC using a one-step procedure. Fatty acids were analysed using a one-step extraction and methylation procedure using methanol:toluene and acetyl chloride in comparison with a two-step procedure involving extraction of lipid using chloroform:methanol and separate methylation. Concentrations of saturated fatty acids including C16:0 and C18:0 were significantly higher (42.6 and 33.9 % respectively) following extraction using the one-step procedure compared with the two-step procedure. However, concentrations of some polyunsaturated fatty acids, including C20:5n-3 and C22:6n-3 were not significantly different between either procedure. The improved detection of fatty acids may be related to the ability of different solvents to extract different lipid fractions. The differential extraction of lipids and detection of fatty acids from sheep RBC may have important implications in studies examining the effect of dietary treatment on the possible health benefits of fatty acids.     

The impact of dietary mono‐ and poly‐unsaturated fatty acids on risk factors for atherosclerosis in humans

The fatty acid composition of the diet has various effects on atherosclerosis risk factors. Dietary saturated fatty acids (SFA) and trans‐unsaturated fatty acids increase the low‐density lipoprotein (LDL)‐/high‐density lipoprotein (HDL)‐cholesterol ratio in serum, while these fats do not have a significant bearing on serum triglyceride levels. By contrast, dietary monounsaturated fatty acids (MUFA), n‐6 polyunsaturated fatty acids (PUFA), and α‐linolenic acid (C18:3n‐3) similarly reduce LDL cholesterol concentrations, while their influence on serum HDL cholesterol and triglycerides is not appreciable. Dietary long‐chain n‐3 PUFA slightly increase serum LDL cholesterol concentrations, but are nevertheless considered salubrious with regard to serum lipids due to the distinct triglyceride‐lowering effects. MUFA‐rich compared to n‐6 PUFA‐rich diets strongly reduce the in vitro oxidizability of LDL. The available studies on this subject also suggest that n‐3 PUFA in the small amounts usually present in the diet are not unduly harmful. These findings are consistent with reports from observational studies: the amount of SFA is positively and the amount of MUFA and n‐6 PUFA in the diet is inversely associated with the risk of cardiovascular disease in most epidemiological studies. The available studies have had an impact on current dietary guidelines, which unanimously recommend that most of the dietary fat should be in the form of MUFA, while the amount of SFA and trans fatty acids in the diet should be as low as possible.     

Dietary modifications of animal fats: status and future perspectives

The purpose of modifying animal fats is to produce high quality products, which meet the dietary recommendations for a reduced intake of fat in the human diet, notably that of certain saturated fatty acids and cholesterol, and an increased intake of mono- (MUFA) and polyunsaturated fatty acids (PUFA) in order to minimize the risk for obesity, cancer, cardiovascular, and other life-style diseases. The body fat of farm animals is partly synthesized from dietary carbohydrates, partly from dietary fatty acids. In monogastric animals, preruminants and poultry PUFAs are readily absorbed and deposited in the edible parts of the body and incorporated into egg yolk lipids. In ruminants, however, PUFAs are hydrogenated to mainly saturated fatty acids by the rumen microorganisms with some formation of MUFAs, trans-, odd-, branched chain, and conjugated fatty acids. The latter fatty acids are absorbed, deposited in adipose and muscle tissue and incorporated into milk lipids, unless dietary PUFAs are protected against hydrogenation. Thus, it is relatively easy to change the fatty acid composition of pork, poultry meat, lamb, and veal, whereas beef and milk can only be enriched significantly with PUFAs by manipulation. Products enriched with PUFAs are, however, prone to oxidation, and enrichment with antioxidants, notably with dietary vitamin E, is necessary in order to prevent the risk of oxidative damage.     

Nonessential fatty acids in formula fat blends influence essential fatty acid metabolism and composition in plasma and organ lipid classes in piglets

The n-6 and n-3 fatty acid status of developing organs is the cumulative result of the diet lipid composition and many complex events of lipid metabolism. Little information is available, however, on the potential effects of the saturated fatty acid chain length (8:0–16:0) or oleic acid (18:1) content of the diet on the subsequent metabolism of the essential fatty acids 18:2n-6 and 18:3n-3 and their elongated/desaturated products. The effects of feeding piglets formulas with fat blends containing either coconut oil (12:0±14:0) or medium chain triglycerides (MCT, 8:0±10:0) but similar levels of 18:1, 18:2n-6 and 18:3n-3, or MCT with high or low 18:1 but constant 18:2n-6 and 18:3n-3 on the fatty acid composition of plasma, liver and kidney triglycerides, phospholipids and cholesteryl esters, and of brain total lipid, were studied. Diet-induced changes in the fatty acid composition of lipid classes were generally similar for plasma, liver and kidney. Dietary 18:1 content was reflected in tissue lipids and was inversely associated with levels of 18:2n-6. Lower percentage of 18:2n-6, however, was not associated with lower levels of its elongated/desaturated product 20:4n-6 but was associated with higher levels of 22:6n-3. Feeding coconut oilvs. MCT resulted in lower 18:1 levels in all lipids, and higher percentages of 20:4n-6 in tissue phospholipid. Increasing the dietary n-6/n-3 ratio from 5 to 8 significantly increased tissue percentage of 18:2n-6 and decreased phospholipid 22:6n-3. In contrast to plasma, liver and kidney, brain lipid fatty acid composition was not influenced by the formula saturated fatty acid chain length, content of 18:1, or n-6/n-3 ratio. In summary, the studies show that the dietary requirement for n-6 and n-3 fatty acids may be influenced by the nonessential saturated and monounsaturated fatty acids fed concurrently.     

Effects of modulation of inflammatory and immune parameters in patients with rheumatic and inflammatory disease receiving dietary supplementation of n-3 and n-6 fatty acids

To describe the rationale and status of n-3 and n-6 fatty acid dietary supplementation in patients with inflammatory disease. The most recent literature is reviewed with a focus on rheumatoid arthritis (RA) as most investigations have described the use of n-3 supplements in this disease entity. Investigations from Europe, the United States, and Australia have described consistent improvement in tender joint scores with many investigators also observing improvements in morning stiffness. A meta analysis has confirmed the predictable improvement in tender joints. Recent studies also suggest that some patients with RA are able to discontinue nonsteroidal anti-inflammatory drugs (NSAIDs) while receiving n-3 fatty acids. A large number of peer reviewed publications from around the world have established the utility of dietary supplementation with n-3 fatty acids in reducing tender joint counts and morning stiffness in patients with RA. Some patients are also able to discontinue NSAIDs while on these supplements.     

Differences in Lipid Characteristics Among Populations: Low-Temperature Adaptability of Ayu, Plecoglossus altivelis

The lipid and fatty acid compositions of the total lipids of three cultured populations (migratory between fresh and salt water, Lake Biwa landlocked, and Setogawa River forms) of ayu, Plecoglossus altivelis, were investigated to clarify the difference in lipid characteristics and temperature adaptability among the three groups. Triacylglycerols were the dominant depot lipids of the three populations, while phospholipids, such as phosphatidylcholine and phosphatidylethanolamine, were found to be the major components of the polar lipids, and their lipid classes are similar to each other. The major fatty acids in the triacylglycerols of all specimens were 16:0, 18:0, 16:1n-7, 18:1n-7, 18:1n-9, 18:2n-6 (linoleic acid), 20:5n-3 (EPA, icosapentaenoic acid), and 22:6n-3 (DHA, docosahexaenoic acid), similar to the tissue phospholipids of the three populations, 16:0, 18:0, 16:1n-7, 18:1n-7, 18:1n-9, 18:2n-6, 20:4n-6, EPA, and DHA. All classes had high levels of 18:2n-6, which originates from their dietary lipids. Compared with the lower DHA levels of the triacylglycerols, the higher levels in the phospholipids suggest their selective accumulation or a biosynthetic pathway to DHA as in freshwater fish. Two populations (the migratory and Setogawa River forms) adapted to lower temperatures with comparatively high levels of polyunsaturated fatty acids (PUFA) for their membrane fluidities. With significantly higher levels of n-3 PUFA and total PUFA, the mean DHA content in the lipids of the Setogawa River form (the population that adapted to lower temperatures) was significantly higher than that of the migratory form. From these results, we concluded that the Setogawa River population actively concentrates long-chain PUFA in its polar lipids and has high adaptability to low temperature.     

Odd chain fatty acids and odd chain phenolic lipids (alkylresorcinols) are essential for diet

Odd chain fatty acids (15:0 and 17:0) from dairy fat as well as odd chain phenolic lipids (alkylresorcinols) from whole grain are commonly reviewed as candidate biomarkers for dietary analysis and their ingestion are inversely related to chronic disease risks. Therefore, low levels of dietary intake of these odd chain molecules may be related to higher risk of physiological states that cause chronic diseases or mortality. It is a prerequisite to examine and understand their main role in beneficial health effects in disease prevention. We propose odd chain fatty acids (OC-FA) and most importantly odd chain phenolic lipids (OC-PL) as potential essential dietary compounds since they play key roles in physiological mechanisms. This review evaluates potential roles of OC-FA and OC-PL in mitigating chronic diseases in vitro and in vivo studies to support our hypothesis for odd chain molecules as essential dietary lipids. Further studies are needed to investigate the relationship between reduced intake of OC-FA- and OC-PL-containing foods and susceptibilities to chronic diseases.     

Fats in indian diets and their nutritional and health implications

To arrive at fat requirements for Indians; the contribution of invisible fat should be determined. Total lipids were extracted from common Indian foods, and their fatty acid compositions were determined. This data and information on intake of various foods were used to estimate the contents of “invisible” fat and fatty acids in Indian diets. Taking into account World Health Organization (WHO) guidelines and the invisible-fat intake of Indians, recommendations were made for lower and upper limits of visible fats. In the rural poor, the “visible”-fat intakes are much lower than estimated minimum requirements. Therefore, to meet the energy needs of low-income groups, particularly young children, visible-fat intakes must be increased to recommended levels. The urban high-income group, however, should reduce dietary fat. Data on intake of various fatty acids in total diet shows that even the recommended lower limit of oil can meet linoleic acid requirements. Intake of α-linolenic acid is low, however. Increase in dietary n-3 polyunsaturated fatty acid (PUFA) produces hypolipidemic, anti-inflammatory, and antithrombotic effects. Effects of n-3 PUFA on blood lipids, platelet fatty acid composition, and platelet aggregation were therefore investigated in Indian subjects consuming cereal-based diets. Supplementation of fish oils (long-chain n-3 PUFA) as well as the use of rapeseed oil (α-linolenic acid) produced beneficial effects. Since the requirements of α-linolenic acid and/or long-chain n-3 PUFA are related to linoleic acid intake, use of more than one oil (correct choice) is recommended for providing a balanced intake of various fatty acids. Analysis of Indian food showed that some foods are good sources of α-linolenic acid. Regular consumption of these foods can also improve the quality of fat in Indian diets. Nonvegetarians, however, have the choice of eating fish to accomplish this.     

Influence of dietary n-3 fatty acids on the membrane properties of skeletal muscle in pigs

The aim of the experiment was the in vivo modification of long-chain fatty acids in phospholipids and to investigate the impact on Ca²⁺ transport of sarcoplasmic reticulum (SR). Ten pigs were fed daily a diet containing 1.3 g n-3 fatty acids/kg diet (control), and ten pigs were fed a diet containing 14 g n-3 fatty acids/kg diet (n-3 diet) during the growing-finishing period. The intake of dietary n-3 fatty acids increased the percentages of these fatty acids in the phospholipids of skeletal muscle sarcoplasmic reticulum (21.6% n-3 fatty acids) and in the polar fraction of total muscle homogenates (30.7% n-3 fatty acids) significantly, compared with control (3.0% and 3.9% n-3 fatty acids, respectively), while the n-6 fatty acid concentration was reduced. In phosphatidylethanolamine of skeletal muscle polar lipids eico-sapentaenoic (EPA) and docosahexaenoic acids (DPA) were increased seven times compared with control. There were no differences in the maximal rate of Ca²⁺ uptake in skeletal muscle SR between the groups. However, the activity of Ca²⁺-ATPase of skeletal muscle SR was elevated in the n-3 diet group. It is suggested, that n-3 fatty acid enriched diet can change the complex membrane composition dependent on experimental conditions and animal species leading to different effects on membrane protein activities.     

Dietary fatty acid profile affects endurance in rats

Typically, athletes are advised to increase their consumption of carbohydrates for energy and, along with the general population, to reduce consumption of saturated fats. It is now recognized that fats are not identical in their influence on metabolism, and we argue that the composition of the polyunsaturated fat component should not be ignored. The aim of this study was to manipulate the dietary fatty acid profile in a high-carbohydrate diet in order to investigate the effect of dietary polyunsaturates on submaximal endurance performance in rats. Rats were fed one of three isoenergetic diets containing 22 energy percentage (E%) fat for 9 wk. The diets comprised an essential fatty acid-deficient diet (containing mainly saturated fatty acids); a diet high in n-6 fatty acids, High n-6; and a diet enriched with n-3 fatty acids, High n-3. Submaximal endurance in rats fed the High n-3 diet was 44% less than in rats fed the High n-6 diet (P<0.02). All rats were then fed a standard commercial laboratory diet for a 6-wk recovery period, and their performances were reevaluated. Although endurance in all groups was lower than at 9 wk, it was again significantly 50% lower in the High n-3 group than the High n-6 group (P<0.005). Although n-3 fats are considered beneficial for cardiovascular health, they appear to reduce endurance times, and their side effects need to be further investigated.