Evaluation of the Impact of Ruminant Trans Fatty Acids on Human Health: Important Aspects to Consider.

The definition and evaluation of trans fatty acids (TFA) with regard to foodstuffs and health hazard are not consistent. Based on the current situation, the term should be restricted only to TFA with isolated double bonds in trans-configuration. Conjugated linoleic acids (CLA) should be separately assessed. Ideally, the origin of the consumed fat should be declared, i.e., ruminant TFA (R-TFA) and industrial TFA (non-ruminant; I-TFA). In ruminant fat, more than 50% of R-TFA consists of vaccenic acid (C18:1 t11). In addition, natural CLA, i.e., c9,t11 CLA is also present. Both are elevated in products from organic farming. In contrast to elaidic acid (t9) and t10, which occur mainly in partially hydrogenated industrial fat, t11 is partially metabolized into c9,t11 CLA via Δ9-desaturation. This is the major metabolic criterion used to differentiate between t11 and other trans C18:1. t11 indicates health beneficial effects in several studies. Moreover, CLA in milk fat is associated with the prevention of allergy and asthma. An analysis of the few studies relating to R-TFA alone makes clear that no convincing adverse physiological effect can be attributed to R-TFA. Only extremely high R-TFA intakes cause negative change in blood lipids. In conclusion, in most European countries, the intake of R-TFA is assessed as being low to moderate. Restriction of R-TFA would unjustifiably represent a disadvantage for organic farming of milk.

Consumption of echium oil increases EPA and DPA in blood fractions more efficiently compared to linseed oil in humans.

BACKGROUND: A plant-based strategy to improve long-chain (LC) omega (n)-3 PUFA supply in humans involves dietary supplementation with oils containing α-linolenic acid (ALA) alone or in combination with stearidonic acid (SDA). The study aimed to compare the effects of echium oil (EO) and linseed oil (LO) on LC n-3 PUFA accumulation in blood and on clinical markers. METHODS: In two double-blind, parallel-arm, randomized controlled studies, all volunteers started with 17 g/d run-in oil (2 weeks). Thereafter, subjects received diets enriched in study 1 with EO (5 g ALA + 2 g SDA; n = 59) or in study 2 with LO (5 g ALA; n = 9) daily for 8 weeks. The smaller control groups received fish oil (FO; n = 19) or olive oil (OO; n = 18). Participants were instructed to restrict their dietary n-3 PUFA intake throughout the studies (e.g., no fish). To investigate the influence of age and BMI on the conversion of ALA and SDA as well as clinical markers, the subjects recruited for EO and LO treatment were divided into three subgroups (two age groups 20-35 y; 49-69 y with BMI 18-25 kg/m(2) and one group with older, overweight subjects (age 49-69 y; BMI >25 kg/m(2)). RESULTS: In plasma, red blood cells (RBC), and peripheral blood mononuclear cells (PBMC), EPA and docosapentaenoic acid (DPA) were ~25 % higher following EO compared to LO. Comparing all treatments, the effectiveness of increasing EPA and DPA in plasma, RBC, and PBMC was on average 100:25:10:0 and 100:50:25:0 for FO:EO:LO:OO, respectively. EO led to a lower arachidonic acid/EPA-ratio compared to LO in plasma, RBC, and PBMC. Following EO, final DHA was not greater compared to LO. Higher BMI correlated negatively with increases in plasma EPA and DPA after EO supplementation, but not after LO supplementation. Decreasing effect on plasma LDL-C and serum insulin was greater with EO than with LO. CONCLUSIONS: Daily intake of SDA-containing EO is a better supplement than LO for increasing EPA and DPA in blood. However, neither EO nor LO maintained blood DHA status in the absence of fish/seafood consumption. TRIAL REGISTRATION: ClinicalTrials.gov Reg No. NCT01856179; ClinicalTrials.gov Reg No. NCT01317290.

Fatty acid profiles and antioxidants of organic and conventional milk from low- and high-input systems during outdoor period.

BACKGROUND: Intensification of organic dairy production leads to the question of whether the implementation of intensive feeding incorporating maize silage and concentrates is altering milk quality. Therefore the fatty acid (FA) and antioxidant (AO) profiles of milk on 24 farms divided into four system groups in three replications (n = 71) during the outdoor period were analyzed. In this system comparison, a differentiation of the system groups and the effects of the main system factors 'intensification level' (high-input versus low-input) and 'origin' (organic versus conventional) were evaluated in a multivariate statistical approach. RESULTS: Consistent differentiation of milk from the system groups due to feeding-related impacts was possible in general and on the basis of 15 markers. The prediction of the main system factors was based on four or five markers. The prediction of 'intensification level' was based mainly on CLA c9,t11 and C18:1 t11, whereas that of 'origin' was based on n-3 PUFA. CONCLUSION: It was possible to demonstrate consistent differences in the FA and AO profiles of organic and standard conventional milk samples. Highest concentrations of nutritionally beneficial compounds were found in the low-input organic system. Adapted grass-based feeding strategies including pasture offer the potential to produce a distinguishable organic milk product quality.

Dietary echium oil increases long-chain n-3 PUFAs, including docosapentaenoic acid, in blood fractions and alters biochemical markers for cardiovascular disease independently of age, sex, and metabolic syndrome.

Dietary supplementation with echium oil (EO) containing stearidonic acid (SDA) is a plant-based strategy to improve long-chain (LC) n-3 (ω-3) polyunsaturated fatty acid (PUFA) status in humans. We investigated the effect of EO on LC n-3 PUFA accumulation in blood and biochemical markers with respect to age, sex, and metabolic syndrome. This double-blind, parallel-arm, randomized controlled study started with a 2-wk run-in period, during which participants (n = 80) were administered 17 g/d run-in oil. Normal-weight individuals from 2 age groups (20-35 and 49-69 y) were allotted to EO or fish oil (FO; control) groups. During the 8-wk intervention, participants were administered either 17 g/d EO (2 g SDA; n = 59) or FO [1.9 g eicosapentaenoic acid (EPA); n = 19]. Overweight individuals with metabolic syndrome (n = 19) were recruited for EO treatment only. During the 10-wk study, the participants followed a dietary n-3 PUFA restriction, e.g., no fish. After the 8-wk EO treatment, increases in the LC n-3 metabolites EPA (168% and 79%) and docosapentaenoic acid [DPA (68% and 39%)] were observed, whereas docosahexaenoic acid (DHA) decreased (-5% and -23%) in plasma and peripheral blood mononuclear cells, respectively. Compared with FO, the efficacy of EO to increase EPA and DPA in blood was significantly lower (∼25% and ∼50%, respectively). A higher body mass index (BMI) was associated with lower relative and net increases in EPA and DPA. Compared with baseline, EO significantly reduced serum cholesterol, LDL cholesterol, oxidized LDL, and triglyceride (TG), but also HDL cholesterol, regardless of age and BMI. In the FO group, only TG decreased. Overall, daily intake of 15-20 g EO increased EPA and DPA in blood but had no influence on DHA. EO lowered cardiovascular risk markers, e.g., serum TG, which is particularly relevant for individuals with metabolic syndrome. Natural EO could be a noteworthy source of n-3 PUFA in human nutrition.

Cheek cell fatty acids reflect n-3 PUFA in blood fractions during linseed oil supplementation: a controlled human intervention study.

BACKGROUND: Adequate biomarkers for the dietary supply of fatty acids (FA) are FA of adipose tissue and blood fractions. In human studies, invasive sample collection is unpleasant for subjects. In contrast, cheek cell sampling can be considered as a non-invasive alternative to investigate FA status.The aim of this study was to analyze whether cheek cell FA composition reflect the supplementation of alpha-linolenic acid (ALA) using a linseed oil mixture compared to olive oil supplementation. Additionally, it was investigated if cheek cell FA composition correlates with the FA composition of plasma, red blood cells (RBC) and peripheral blood mononuclear cells (PBMC) before and during both interventions. METHODS: During a 10-week randomized, controlled, double-blind human intervention study, 38 subjects provided cheek cell and blood samples. After a two-week run-in period, the test group (n = 23) received 17 g/d of an ALA-rich linseed oil mixture, while the control group (n = 15) received 17 g/d of an omega-3 (n-3) polyunsaturated FA (PUFA)-free olive oil. Cheek cells and blood were collected on days 0, 7 and 56 of the 8-week intervention period. RESULTS: Compared to olive oil, the linseed oil intervention increased ALA and also the endogenously converted long-chain n-3 metabolites eicosatetraenoic-, eicosapentaenoic- and docosapentaenoic acid in cheek cells (P ≤ 0.05). Docosahexaenoic acid remained unchanged. Reflecting the treatment, the n-6/n-3 ratio decreased in the test group. In general, cheek cell FA reflected the changes of FA in blood fractions. Independent of treatment, significant correlations (P ≤ 0.05) of n-6 PUFA and n-3 PUFA between cheek cells and plasma, RBC and PBMC were found, except for linoleic acid and ALA. CONCLUSIONS: The changes in FA composition of cheek cells confirmed that ALA from linseed oil increased endogenously derived n-3 PUFA in cheek cell lipids. These changes in cheek cells and their correlation to the respective FA in blood fractions indicate the cheek cell FA profile as an adequate non-invasive biomarker for short-term n-3 PUFA intake and metabolism. Therefore, cheek cell FA can be used in human intervention studies or large-scale epidemiological studies, especially for assessment of the n-3 PUFA status. TRIAL REGISTRATION: ClinicalTrials.gov, IDNCT01317290.

Survey of n-3 and n-6 polyunsaturated fatty acids in fish and fish products.

BACKGROUND: The imbalance of the n-3/n-6 ratio in the Western diet is characterised by a low intake of n-3 long-chain (LC) PUFA and a concurrent high intake of n-6 PUFA. Fish, in particular marine fish, is a unique source of n-3 LC PUFA. However, FA composition of consumed fish changed, due to the increasing usage of n-6 PUFA-rich vegetable oils in aquaculture feed and in fish processing (frying) which both lead to a further shift in n-6 PUFA to the detriment of n-3 LC PUFA.The aim of this study was to determine the ratio of n-3/n-6 including the contents of EPA and DHA in fish fillets and fish products from the German market (n=123). Furthermore, the study focussed on the FA content in farmed salmon compared to wild salmon as well as in processed Alaska pollock fillet, e.g., fish fingers. RESULTS: Total fat and FA content in fish products varied considerably depending on fish species, feed management, and food processing. Mackerel, herring and trout fillets characteristically contained adequate dietary amounts of absolute EPA and DHA, due to their high fat contents. However, despite a lower fat content, tuna, pollock, and Alaska pollock can contribute considerable amounts of EPA and DHA to the human supply.Farmed salmon are an appropriate source of EPA and DHA owing to their higher fat content compared to wild salmon (12.3 vs. 2.1 wt %), however with elevated SFA, n-9 and n-6 FA contents representing the use of vegetable oils and oilseeds in aquaculture feed. The n-3/n-6 ratio was deteriorated (2.9 vs. 12.4) but still acceptable. Compared to pure fish fillets, breaded and pre-fried Alaska pollock fillet contained extraordinarily high fat and n-6 PUFA levels. CONCLUSIONS: Since fish species vary with respect to their n-3 LC PUFA contents, eating a variety of fish is advisable. High n-6 PUFA containing pre-fried fish support the imbalance of n-3/n-6 ratio in the Western diet. Thus, consumption of pure fish fillets is to be favoured. The lower n-3 PUFA portion in farmed fish can be offset by the higher fat content, however, with an unfavourable FA distribution compared to wild fellows.

Influence of in vitro supplementation with lipids from conventional and Alpine milk on fatty acid distribution and cell growth of HT-29 cells.

BACKGROUND: To date, the influence of milk and dairy products on carcinogenesis remains controversial. However, lipids of ruminant origin such as conjugated linoleic acids (CLA) are known to exhibit beneficial effects in vitro and in vivo. The aim of the present study was to determine the influence of milk lipids of different origin and varying quality presenting as free fatty acid (FFA) solutions on cellular fatty acid distribution, cellular viability, and growth of human colon adenocarcinoma cells (HT-29). METHODS: FAME of conventional and Alpine milk lipids (MLcon, MLalp) and cells treated with FFA derivatives of milk lipids were analyzed by means of GC-FID and Ag+-HPLC. Cellular viability and growth of the cells were determined by means of CellTiter-Blue®-assay and DAPI-assay (4',6-diamidino-2-phenylindole dihydrochloride), respectively. RESULTS: Supplementation with milk lipids significantly decreased viability and growth of HT-29 cells in a dose- and time-dependent manner. MLalp showed a lower SFA/MUFA ratio, a 8 fold increased CLA content, and different CLA profile compared to MLcon but did not demonstrate additional growth-inhibitory effects. In addition, total concentration and fatty acid distribution of cellular lipids were altered. In particular, treatment of the cells yielded highest amounts of two types of milk specific major fatty acids (µg FA/mg cellular protein) after 8 h of incubation compared to 24 h; 200 µM of MLcon (C16:0, 206 ± 43), 200 µM of MLalp (C18:1 c9, (223 ± 19). Vaccenic acid (C18:1 t11) contained in milk lipids was converted to c9,t11-CLA in HT-29 cells. Notably, the ratio of t11,c13-CLA/t7,c9-CLA, a criterion for pasture feeding of the cows, was significantly changed after incubation for 8 h with lipids from MLalp (3.6 - 4.8), compared to lipids from MLcon (0.3 - 0.6). CONCLUSIONS: Natural lipids from conventional and Alpine milk showed similar growth inhibitory effects. However, different changes in cellular lipid composition suggested a milk lipid-depending influence on cell sensitivity. It is expected that similar changes may also be evident in other cell lines. To our knowledge, this is the first study showing a varied impact of complex milk lipids on fatty acid distribution in a colon cancer cell line.

High content of long-chain n-3 polyunsaturated fatty acids in red blood cells of Kenyan Maasai despite low dietary intake.

BACKGROUND: Increasing land restrictions and a reduced livestock-to-human ratio during the 20th century led the Maasai to lead a more sedentary, market-orientated lifestyle. Although plant-derived food nowadays contributes substantially to their diet, dairy products being high in saturated fatty acids (SFA) and low in polyunsaturated fatty acids (PUFA) still are an important energy source. Since reliable data regarding the Maasai diet date back to the 1980s, the study objective was to document current diet practices in a Kenyan Maasai community and to investigate the fatty acid distribution in diet and red blood cells. METHODS: A cross-sectional study was conducted among 26 Maasai (20 women, 6 men) from Loodokilani, Kajiado District, Kenya. Food intake was described by the subjects via 24-h recall, and both food and blood samples were analysed. RESULTS: Two main foods--milk and ugali--constituted the Maasai diet in this region. A total of 0.9 L of milk and 0.6 kg of ugali were consumed per person and day to yield an energy intake of 7.6 MJ/d per person. A major proportion of ingested food contributing 58.3% to the total dietary energy (en%) was plant-derived, followed by dairy products representing 41.1 en%. Fat consumed (30.5 en%) was high in SFA (63.8%) and low in PUFA (9.2%). Long-chain n-3 PUFA (EPA, DPA and DHA) made up only 0.15% of the ingested fatty acids, but 5.9% of red blood cell fatty acids. CONCLUSION: The study indicates the Maasai diet is rich in SFA and low in PUFA. Nevertheless, red blood cells are composed of comparable proportions of long-chain n-3 PUFA to populations consuming higher amounts of this fatty acid group.

Fatty acid distribution of cord and maternal blood in human pregnancy: special focus on individual trans fatty acids and conjugated linoleic acids.

BACKGROUND: Maternal nutrition in pregnancy has a crucial impact on the development of the fetus. Dietary trans fatty acids (tFA) are known to have adverse health effects, especially during pregnancy. However, the distribution of tFA produced via partial hydrogenation of vegetable oils (mainly elaidic acid; t9) differs compared to ruminant-derived tFA (mainly vaccenic acid; t11). Recent findings indicate that they may have different impact on human health.Therefore, in this study, plasma and erythrocytes of mother-child pairs (n = 55) were sampled to investigate the distribution of tFA, including individual trans C18:1 fatty acids and conjugated linoleic acids (CLA) in fetal related to maternal lipids; with additional consideration of maternal dairy fat intake. RESULTS: Portion of t9 and t11, but also of c9,t11 CLA was higher in maternal than in fetal blood lipids. The portion of t9 in maternal and fetal lipids differed only slightly. In contrast, the portion of fetal t11 was only half of that in maternal blood. This led to a fetal t9/t11-index in plasma and erythrocytes being twice as high compared to the maternal values. A high dairy fat intake resulted in elevated portions of t11 and its Δ9-desaturation product c9,t11 CLA in maternal blood. In contrast, in the respective fetal blood lipids only c9,t11 CLA, but not t11 was increased. Nevertheless, a positive association between maternal and fetal plasma exists for both t11 and c9,t11 CLA. Furthermore, in contrast to t9, t11 was not negatively associated with n-3 LC-PUFA in fetal blood lipids. CONCLUSIONS: Fetal blood fatty acid composition essentially depends on and is altered by the maternal fatty acid supply. However, in addition to dietary factors, other aspects also contribute to the individual fatty acid distribution (oxidation, conversion, incorporation). The lower portion of fetal t11 compared to maternal t11, possibly results from Δ9-desaturation to c9,t11 CLA and/or oxidation. Based on the fatty acid distribution, it can be concluded that t11 differs from t9 regarding its metabolism and their impact on fetal LC-PUFA.

Dietary supplementation with 11trans- and 12trans-18:1 and oxidative stress in humans.

BACKGROUND: High consumption of trans fat has been associated with high oxidative stress in humans, which could increase the risk of the development or acceleration of several diseases, such as atherosclerosis, cancer, and type 2 diabetes. OBJECTIVE: Several urinary and blood biomarkers of oxidative stress [8-iso-prostaglandin-F(2alpha) (PGF(2alpha)), 15-keto-dihydro-PGF(2alpha), and 7,8-dihydro-8-oxo-2'-deoxy-guanosine in urine and alpha-,beta-,gamma-,delta-tocopherol, and retinol in plasma] were monitored to evaluate the oxidative stress induced by dietary supplementation of 11trans- and 12trans-18:1 isomers in humans during a 6-wk intervention. DESIGN: After a 14-d adaptation period free of trans fatty acid supplementation (baseline), the test group (n = 12) received 3.0 g 11trans-18:1/d and 3.0 g 12trans-18:1/d (Sigma 6.0 g/d), and the control group (n = 12) consumed a control oil free of trans fatty acids and conjugated linoleic acids for 6 wk. RESULTS: The postintervention concentration of urinary 8-iso-PGF(2alpha) (free radical-induced lipid peroxidation) in the test group was significantly higher than baseline and significantly higher than that observed in the control group. The concentrations of 15-keto-dihydro-PGF(2alpha) (cyclooxygenase-mediated inflammatory response indicator) and 7,8-dihydro-8-oxo-2'-deoxy-guanosine (oxidative DNA damage) were not affected by the 11trans- and 12trans-18:1 supplementation. CONCLUSIONS: Although an increase in urinary 8-iso-PGF(2alpha) was observed and the effects of prolonged high (ie, >5.0 g/d) consumption of trans fat could be relevant to the development of disease, the mean intakes of 11trans- and 12trans-18:1 in Europeans are estimated to be significantly below the amounts administered in this study (ie, 6.0 g/d); such low intakes could minimize the possible risk of detrimental effects on human health.

Foetal cord blood contains higher portions of n-3 and n-6 long-chain PUFA but lower portions of trans C18:1 isomers than maternal blood.

BACKGROUND/OBJECTIVE: An adequate supply of long-chain polyunsaturated fatty acids (LC PUFA) promotes foetal health and development, whereas generally, trans fatty acids (tFA) are considered to negatively interfere with LC PUFA metabolism. Nevertheless, to date, limited data concerning separate trans C18:1, such as t9 and t11, are available for maternal and foetal blood. Therefore, in this study the portions of individual trans C18:1, LC n-6, and n-3 PUFA in lipids of maternal and foetal plasma and erythrocyte membranes of German mother and child pairs (n=40) were analysed. RESULTS: Portions of linoleic acid and α-linolenic acid as LC precursors were lower (~0.4-fold); whereas the metabolites arachidonic acid (AA, n-6) and docosahexaenoic acid (DHA, n-3) were significantly higher (~2-fold) in foetal than in maternal plasma and erythrocytes. The main tFA in maternal and foetal blood were elaidic acid (C18:1t9; t9) and vaccenic acid (C18:1t11; t11). Portions of t9, t10, t11, and t12 in foetal blood lipids were lower (~0.5-fold) compared with maternal blood. In foetal lipids, t9 was higher than t11. The t9 correlated negatively with eicosapentaenoic acid (n-3) and AA in maternal and foetal lipids; whereas t11 correlated negatively only with foetal total LC n-6 (plasma and erythrocytes) and n-3 PUFA (erythrocytes). No correlation between maternal tFA and foetal PUFA was observed. CONCLUSIONS: 'Biomagnification' of LC n-6 and n-3 PUFA AA and DHA in foetal blood was confirmed, whereas single trans isomers were lower compared with maternal blood. Nevertheless, tFA intake, especially from industrial sources, should be as low as possible.

trans Palmitoleic acid arises endogenously from dietary vaccenic acid.

BACKGROUND: trans Palmitoleic acid (t-16:1n-7, or 16:1 t9 in the δ nomenclature usually applied to trans fatty acids and used herein) arouses great scientific interest because it has been suggested to serve as a biomarker for lower risks of type 2 diabetes and coronary artery disease. OBJECTIVE: Although 16:1 t9 has been assumed to derive from dietary sources, we examined the hypothesis that 16:1 t9 might also be endogenously produced from its metabolic precursor vaccenic acid (t-18:1n-7 or 18:1 t11). DESIGN: We reevaluated fatty acid data obtained from one human intervention study and one cellular model in both of which 18:1 t11 was supplemented. Both studies have already been published, but to our knowledge, 16:1 t9 has not yet been considered. This reanalysis of the datasets was reasonable because a new methodology for identifying 16:1 cis and trans isomers allowed us to address the subject presented in this article. RESULTS: Data showed that the systemic or intracellular increase in 16:1 t9 was strongly correlated with the increase in 18:1 t11 after the dietary intake or cellular uptake of 18:1 t11. The conversion rate in humans was, on average, 17%. CONCLUSION: Our findings suggest that endogenous 16:1 t9 is not, as has been assumed, exclusively diet derived but may also be produced by the partial ß oxidation of dietary 18:1 t11.

Separation of the fatty acids in menhaden oil as methyl esters with a highly polar ionic liquid gas chromatographic column and identification by time of flight mass spectrometry.

The fatty acids contained in marine oils or products are traditionally analyzed by gas chromatography using capillary columns coated with polyethylene glycol phases. Recent reports indicate that 100 % cyanopropyl siloxane phases should also be used when the analyzed samples contain trans fatty acids. We investigated the separation of the fatty acid methyl esters prepared from menhaden oil using the more polar SLB-IL111 (200 m × 0.25 mm) ionic liquid capillary column and the chromatographic conditions previously optimized for the separation of the complex mixture of fatty acid methyl esters prepared from milk fat. Identifications of fatty acids were achieved by applying Ag(+)-HPLC fractionation and GC-TOF/MS analysis in CI(+) mode with isobutane as the ionization reagent. Calculation of equivalent chain lengths confirmed the assignment of double bond positions. This methodology allowed the identification of 125 fatty acids in menhaden oil, including isoprenoid and furanoid fatty acids, and the novel 7-methyl-6-hexadecenoic and 7-methyl-6-octadecenoic fatty acids. The chromatographic conditions applied in this study showed the potential of separating in a single 90-min analysis, among others, the short chain and trans fatty acids contained in dairy products, and the polyunsaturated fatty acids contained in marine products.

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.

Trans fatty acid isomers and the trans-9/trans-11 index in fat containing foods.

To determine trans fatty acid (TFA) distribution of contemporary foods, especially regarding individual trans octadecenoic acids (trans C18:1), 339 German foods of six categories (semi-solid fats, deep-fried potato products, bakery products, confectioneries, instant products and butter) were analysed using two GC methods. Results showed a high variation of TFA content between and within the categories containing between 0 and 40.5% of FAME except in butter, which is a source of natural TFA. The mean TFA values were below 2.0% of FAME, however, bakery products contained 4.5% and butter fat 3.2%, respectively. In addition, the distribution of individual trans C18:1 differed. In samples containing ruminant fat (butter and various confectioneries), vaccenic acid (t11-C18:1, t11) predominated, while in foods containing industrially hydrogenated fats, elaidic acid (trans-9, t9-) and t10-C18:1 were the major trans isomers.. This was reflected by a low t9/t11 index of 0.3 and 0.5 in butter and ruminant fat containing confectioneries, respectively, whilst the highest index was observed in shortenings and deep-fried potato products at 5.2 and 6.8, respectively. In conclusion, the TFA content of foods available on the German market is generally declining, but substantial variations are present. The t9/t11 index could be used as an indicator to determine ruminant fat.Practical applications: A number of studies provide evidence that a high TFA intake, particularly of industrial origin, adversely affects human health. The TFA content of foods could be reduced due to the introduction of several mandatory regulations and modifications regarding the hydrogenation process of oils. The most abundant dietary TFA are the isomers of trans C18:1. Unfortunately, the differentiation of these isomers is not yet very common, though the trans C18:1 profile differs depending on its origin (bacterial hydrogenation in the rumen or industrial hydrogenation). To date, data for TFA content including the trans C18:1 profile of different food categories are limited. The present study confirmed that the TFA contents in German foods are declining. However, TFA are still elevated, especially in bakery products and confectioneries, which are produced using mainly industrial but also ruminant fats. Therefore, the t9/t11 index imparts important information on the source of TFA in processed foods.

2-Propanol in the mobile phase reduces the time of analysis of CLA isomers by silver ion-HPLC.

Individual isomers of octadecadienoic acid (C18:2) with conjugated double bonds (conjugated linoleic acids; CLA) exert different biological activities. Their distribution in food and tissues differs. Therefore, the separation of the various positional and geometric isomers is important. The time of analysis using silver ion-high performance liquid chromatography can extend up to 90 min. The aim of this study was to reduce this time. The time of analysis reduced from ca. 90 min onto 45 to 35 min, respectively, by the addition of 0.05% or 0.1% (v/v) 2-propanol to the mobile phase [acetonitrile (0.1%; v/v) and diethyl ether (0.5%; v/v) in n-hexane]. There was no effect on resolution of the 17 individual CLA isomers of the CLA mixture. Regarding the lowest coefficient of variation and an adequate baseline separation the use of 0.05% 2-propanol in the mobile phase is recommended, without any disadvantages and adverse effects on the service life of columns. In conclusion, adding 0.05% or 0.1% 2-propanol to the mobile phase shortens the time of analysis of CLA isomers, saves solvents and reduces costs.

Dietary supplementation with trans-11- and trans-12-18 : 1 increases cis-9, trans-11-conjugated linoleic acid in human immune cells, but without effects on biomarkers of immune function and inflammation.

Trans-fatty acid intake is associated with an increased risk of CHD and diabetes. The effects of single trans-fatty acid isomers are largely unexplored. The present study examined the effects of a 6-week supplementation with two trans-18 : 1 isomers (trans-11 and trans-12) in human subjects on immune cells, several inflammatory and immunological biomarkers (for example, IL, TNFalpha, C-reactive protein, adiponectin, intercellular adhesion molecule-1, prostacyclin, phagocytic process). Following a 2-week adaptation period without supplements, the test group (n 12) received vaccenic acid (trans-11-18:1) and trans-12-18 : 1 in equal amounts (6.0 g/d) for 6 weeks. The control group (n 12) consumed an oil without trans-fatty acids and conjugated linoleic acids (CLA). Samples were collected at the end of both periods. Trans-11- and trans-12-18 : 1 were significantly increased in cellular lipids. The endogenous synthesis of cis-9, trans-11-CLA from trans-11-18 : 1 was demonstrated via increased CLA in cellular lipids of the test group. Generally, trans-isomer supplementation did not affect either inflammatory biomarkers (for example, IL-6, IL-8, TNFalpha) or immune function (for example, phagocytosis) during the present study. The dietary supplementation of trans-11- and trans-12-18 : 1 (6 g/d) and their accumulation in leucocytes had no effects on biomarkers of inflammation and immune function. However, because of the limited data on the safety of trans-fatty acid intake and effects of individual trans isomers on human health (for example, trans-9-18 : 1, trans-10-18 : 1) at present, it is prudent to reduce trans-fat intake in general.

Trans-11-18 : 1 is effectively Delta9-desaturated compared with trans-12-18 : 1 in humans.

The aim of this human intervention study was to evaluate the Delta9-desaturation of trans-11-18 : 1 (trans-vaccenic acid; tVA) to cis-9,trans-11-18 : 2 (c9,t11 conjugated linoleic acid; CLA) and of trans-12-18 : 1 (t12) to cis-9,trans-12-18 : 2 after a short-term (7 d) and a long-term (42 d) supplementation period. The conversion rates of both trans-18 : 1 isomers were estimated by lipid analysis of serum and red blood cell membranes (RBCM). Subjects started with a 2-week adaptation period without supplements. During the 42 d intervention period, the diet of the test group was supplemented with 3 g/d of tVA and 3 g/d of t12. The diet of the control group was supplemented with a control oil. Serum tVA and t12 levels in the test group increased by fivefold and ninefold after 7 d, respectively, and by eight- and 12-fold after 42 d, respectively, when compared with the adaptation period (P< or =0.002). The serum c9,t11 CLA levels increased by 1.7- and 2.0-fold after 7 d and 42 d, respectively (P< or =0.001). After 42 d, the test group's RBCM c9,t11 CLA content was elevated by 20 % (P=0.021), whereas in the control group it was decreased by 50 % (P=0.002). The conversion rate of tVA was estimated at 24 % by serum and 19 % by RBCM. No increase in c9,t12-18 : 2 was observed in the serum and RBCM, and thus no conversion of t12 could be determined. In conclusion, the endogenous conversion of dietary tVA to c9,t11 CLA contributes approximately one quarter to the human CLA pool and should be considered when determining the CLA supply.