Similar distribution of trans fatty acid isomers in partially hydrogenated vegetable oils and adipose tissue of Canadians

Determination of the fatty acid composition and fatty acids trans-isomers in the horse, stall horse, mutton, beef and pork meat

In this study, we have focussed on the fatty acid composition of the meat of various animals raised in the Republic of Kazakhstan. We have analyzed pasture horse meat, stall horse meat, lamb, beef, and pork meat. Samples from four carcass muscles (back, hip, rib, and neck) were tested. Comparative analysis of the content of trans isomers of fatty acids (TFA) was performed. The analysis of the obtained samples showed that the TFA content is significantly (p <0.05) different in different parts of the carcasses of all animals. Their highest content was observed in the mutton sample, which reached 79.56-82.04%. The beef was next after mutton (6.20-9.64%). Less than in mutton and beef, but more than in pork and TFAs were contained in stall horse meat (2.75-5.52%). Of the two types of horse meat, there was less TFA in horse meat of pasture content (1.85-3.46%). Compared to all studied samples, the lowest level of trans fatty acids was in pork (0.91-1.39%). In horse meat of both types, TFAs were present in trans-9-C16: 1. More types of TFA were found in the meat of other animals: in mutton (trans-9-C14: 1; trans-9-C16: 1; trans-9-C18: 1; trans-11 C18: 1; trans-9-trans- 12-C18: 2), in beef (trans-9-C16: 1; trans-9-C18: 1; trans-11-C18: 1; trans-9-trans-12-C18: 2), in pork (trans-9-C16: 1). In addition to TFA, an analysis was made of the ratio of omega-6 and omega-3 (ω-6: ω-3). Considering that the lower the ratio of ω-6: ω-3 in fat, the healthier it is for the human body, the most optimal among the studied samples in terms of the ratio of ω-6: ω-3 fatty acids was mutton (1.83-2.35) and horse meat of stall keeping (1.76-6.53). The most unfavourable ratios were in the pork samples (17.46-35.69). The ratio ω-6: ω-3 in other animals was within the following limits: beef (5.35-9.13), horse meat of pasture content (7.08-10.50).

Contaminating fat in pericardial suction blood: a clinical, technical and scientific challenge

Stroke and diffuse brain damage after cardiac surgery are too common. It is important to find means to reduce the incidence in view of future competition to surgery from less invasive procedures. Stroke is fairly well defined in clinical terms and with several identified mechanisms. Diffuse brain damage is less well defined and more complex in nature. One suggested mechanism is from cerebral fat microembolization of retrieved pericardial suction blood (PSB). The present study aimed to describe a simple method to measure fat content of PSB, how experimental artefacts interfere with the results, and how the unstable character of a fat-blood suspension can be used to design a simple fat-separation system. The quantity of small amounts of fat can be amplified by centrifugation to the tapered tip of a standard glass pipette. The coefficient of variation after repeated experiments was 9.5%. PSB after coronary bypass surgery contained 0.22±0.04% fat of which 15±3% was bound to the surface of the plastic collecting bag. Experimentation requires standardized routines. Static incubation, blood-fat mixing routines, and transfer steps of blood samples between syringes induce substantial artefacts from spontaneous density separation and surface-adhesion of fat. Soya oil is a common reference substance replacing human fat in technical laboratory science, but is associated with artefacts of its own. These artefacts cause problems during experimentation but the oil is a good resource in the design of a simple fat-separation system

Trans fatty acids and cardiovascular health: translation of the evidence base

BACKGROUND AND AIM

The recent interest in the development of evidence-based nutrition recommendations has resulted in the development of frameworks which enable a more structured evaluation of the link between diet and chronic disease. This paper examines the application of the frameworks produced by the Scottish Intercollegiate Guidelines Network (SIGN) and the World Cancer Research Fund (WCRF), by using as a case study the association between trans unsaturated fatty acids (TFAs) and coronary heart disease. TFAs arise during industrial hydrogenation of vegetable or fish fats and oils and the natural digestion process in ruminant animals.

DATA SYNTHESIS

Numerous studies have examined the effects of TFA intake on serum lipids and lipoproteins and the association between TFA consumption and cardiovascular disease. Metabolic studies and meta-analyses show a clear and consistent association between increasing TFA intakes and an adverse lipid profile. Evidence from case-control and prospective cohort studies examining the association between TFA intakes and coronary heart disease is more heterogeneous and there are limitations in several of the studies.

CONCLUSION

While the evidence is sufficient to suggest a probable positive association between TFAs and coronary heart disease, and thus to justify a firm recommendation for a reduction in dietary TFA intake, the evaluation of the data underlines the difficulties in extrapolating the principles of evidence-based medicine to evidence-based nutrition. Furthermore, there is a paucity of research into the effects of animal-derived TFAs in amounts typically consumed in a western diet and their association with adverse lipid profiles or cardiovascular outcomes.

Replacements for trans fats-will there be an oil shortage?

Manufacturers use the process of hydrogenation to create trans fats in order to increase the shelf life of baked and fried foods. Ingestion of trans fats is associated with an increased risk of cardiovascular disease. A groundswell of public sentiment is causing regulatory bodies to ban the use of trans fats in foods. Alternatives to trans fats are needed now in order to preserve the freshness and provide an appealing texture of many packaged foods. As trans fats become phased out, there are eight types of approaches currently being developed to substitute for these fats as ingredients for baked and fried foods: (1) modified hydrogenation, (2) genetically modified seeds, (3) interesterification, (4) fractionation and blending, (5) butter and animal fat, (6) natural saturated oils, (7) natural unsaturated oils, and (8) fat substitutes. These alternatives to trans fats will require close scrutiny to ascertain whether they will also turn out to be linked with cardiovascular disease.

Trans-18∶1 isomers in rat milk fat as effective biomarkers for the determination of individual isomeric trans-18∶1 acids in the dams' diet

Female rats were fed a diet containing by weight 10% partially hydrogenated sunflower oil, 2% sunflower oil, and 1% rapeseed oil during gestation and lactation. The trans-18:1 isomer profile of the fat supplement was (in % of total trans 18:1 acids in the fat supplement): delta4, 0.5; delta5, 1.0; delta6-delta8, 18.0; delta9 (elaidic), 13.5; delta10, 22.2; delta11 (vaccenic), 16.0; delta12, 11.3; delta13-delta14, 12.8; delta15, 2.5; and delta16, 2.2 (total trans 18:1 acids in the fat supplement: 40.6%). The cis 18:1 isomer profile was (in % of total cis-18:1 isomers): delta6-delta8, 2.1; delta9 (oleic), 70.9; delta10, 6.1; delta11, 8.3; delta12, 4.0; delta13, 2.8; delta14, 4.6, and delta15, 1.2 (total cis-18:1 acids in the fat supplement: 32.6%). Suckling rats from four litters were sacrificed at day 17 or 18 after birth, and their stomach content (milk) was analyzed. The trans-18:1 isomer profile of milk was (relative proportions, in % of total): delta4, 0.3; delta5, 1.1; delta6-delta8, 16.8; delta9, 15.3; delta10, 22.0; delta11, 16.7; delta12, 11.8; delta13-14, 11.8; delta15, 2.5, and delta16, 1.9 (total trans 18:1 acids in milk: %). That of cis-18:1 isomers was (proportions in % relative to total cis-18:1 isomers): delta6-delta8, 4.7; delta9, 72.5; delta10, 4.0; delta11, 8.0; delta12, 7.1; delta13, 1.9; delta14, 1.0, and delta15, 0.7 (total cis-18:1 acids in milk: %). These results demonstrate that all isomeric acids, independent of the geometry and the position of the ethylenic bond, are incorporated into milk lipids. With regard to trans-18:1 isomers, the distribution profile in milk is identical to that in the dams' diet, i.e., there is no discrimination against any positional isomer between their ingestion and their deposition into milk lipids. As a consequence, this study indicates that the trans-18:1 isomer profile of milk reflects that in the dams' diet and supports our earlier hypothesis that the profile of trans-18:1 isomers in milk can be used to deduce the relative contribution of ruminant fats and partially hydrogenated oils in the diet to the total intake of trans-18:1 isomers. On the other hand, the cis-18:1 isomer profile in milk shows significant differences when compared to that in the dams' diet. Surprisingly, there are no major differences for the cis-delta9 (oleic) and the cis-delta11 (asclepic) isomers, which can be synthesized by the mother. However, there seems to be a significant positive selectivity for the group cis-delta6-delta8, and for the cis-delta12 isomer, whereas a negative selectivity occurs for the delta10 and delta13 to delta15 cis isomers.

The embolic potential of liquid fat in pericardial suction blood, and its elimination

Diffuse brain damage is a complex problem in cardiac surgery postoperatively. Liquid fat from recycled pericardial suction blood (PSB) is an embolic source. PSB can be discarded, but the recycling can be life saving, and methods have been developed to remove the fat. Blood washing by centrifugation is suggested to be the most effective method. In retained PSB, fat also separates without centrifugation, which is a novel and simple approach. Alternatively, inline fat filtration is easily accomplished but its effectiveness has been questioned. The present study aimed to investigate this phenomenon. Fat was heat extracted from retrieved pericardial fat tissue of coronary artery bypass graft (CABG) patients (n = 6), and was mixed, 1.25%, with postoperative mediastinal-shed blood. The mixture was filtered using a LipiGuard SB at constant flow rate. The filtration was scaled down to 3 mL and performed under temperature control, 37 degrees C, 20 degrees C and 10 degrees C. At these temperatures fat removal was 46.9 +/- 6.1%, 61.5 +/- 7.0% and 76.8 +/- 5.0%, respectively, with a statistical difference of P = 0.001. The improved fat removal at low temperature dramatically increased filtration pressures (P < 0.001) and caused haemolysis (P = 0.018). It is concluded that fat filtration is technically difficult. Cooling of blood increases fat extraction, but with negative side effects due to filter occlusion.

Fat reduction in pericardial suction blood by spontaneous density separation: an experimental model on human liquid fat versus soya oil

Pericardial suction blood (PSB) contains mediastinal liquid wound fat with an embolic potential to cause brain damage after cardiopulmonary bypass (CPB). The aims were to measure how fat separates spontaneously from blood by density and how temperature and fat surface adhesion affect the results under experimental conditions. Human liquid fat was heat-extracted from retrieved pericardial fat tissue of coronary artery bypass graft (CABG) patients (n = 10). Human fat or soya oil, 5% and 10%, respectively, were mixed with postoperatively shed mediastinal blood (n = 20). The mixture was loaded into a temperature-controlled (37 degrees C, 20 degrees C, 10 degrees C) vertical separation column. At 1, 2.5, 5 and 10 minutes, the blood was collected in five fractions, representing layers of density separation, followed by centrifugation. Human fat solidified at 8 degrees C. Soya oil remained liquid below 0 degrees C. Soya oil separated fast in water, but was slower in blood. At 10 minutes and 37 degrees C 73 +/- 6% of added soya oil was found in the top 20% fraction. Human fat at 37 degrees C behaved similarly to soya oil, with 58 +/- 2% separation at 10 minutes. However, at lower temperatures the density separation became less efficient (p < 0.001), whereas human fat more effectively adhered to the walls of the column, which added to the removal. In total, 66%-78% of the human fat was removed, depending on temperature. In conclusion, fat in PSB can be reduced by simple density separation and surface adhesion while it is temporarily retained from the CPB circuit.

The rationale for fat filtration during cardiac surgery

Improved filter technology may enable the removal of specific substances such as lipids from the blood. Lipids form a heterogeneous group of compounds, but during surgery, the main interest is focussed on triglycerides, glycerol and free fatty acids. Fat emboli have been demonstrated in the brain after cardiac surgery and are associated with ischaemic brain injury. Fat emboli have also been demonstrated in lung and kidney tissue. Lung tissue and leucocytes are especially vulnerable to the effects of free fatty acids. The surgical wound suction blood during cardiac surgery contains a considerable quantity of microemboli. Therefore, as a first step to determining the place of fat filtration during cardiac surgery, the use of a fat removal filter for surgical wound suction blood is advocated.

Accumulation and apparent oxidation of cis,trans-18 : 2 isomers relative to linoleic acid in rats

Dietary cis,trans-18 : 2 isomers impair desaturation and elongation of linoleic acid (Delta9cis,12cis-18 : 2), but little is known of their proportional partitioning between accumulation and oxidation. The present study was therefore designed to assess the accumulation and apparent oxidation of cis,trans-18 : 2 isomers compared with that of trans-18 : 1 isomers and Delta9cis,12cis-18 : 2 in rats. Accumulation is defined as whole-body increase in a fatty acid during a given period (i.e. final body content-initial body content). The apparent oxidation (disappearance) is defined as whole-body utilization of a fatty acid relative to its intake for a given period (intake-excretion-accumulation-longer-chain products)/intakex100). The animals were fed on a diet containing 15 % (w/w) partially hydrogenated rapeseed oil with 1.72 % energy as cis,trans-18 : 2 isomers and varying amounts of Delta9cis,12cis-18 : 2. The apparent oxidation of total cis,trans-18 : 2 isomers (72-76 % dietary intake) was greater than that of Delta9cis,12cis-18 : 2 (38-51 % dietary intake) but it was similar to that of total trans-18 : 1 isomers (78-82 % dietary intake). Among the four isomers, the apparent oxidation of Delta9trans,12trans-18 : 2 was greater than that of the other isomers including Delta9trans,12cis-18 : 2, Delta9cis,12trans-18 : 2 and Delta9cis,13trans-18 : 2. Accumulation of Delta5cis,8cis,11cis,15trans-20 : 4 and Delta5cis,8cis,11cis,14trans-20 : 4 derived from chain-elongation and desaturation of Delta9cis,13trans-18 : 2 and Delta9cis,12trans-18 : 2 was decreased when the dietary Delta9cis,12cis-18 : 2 supply was increased.

Follow-up of the delta4 to delta16 trans-18:1 isomer profile and content in French processed foods containing partially hydrogenated vegetable oils during the period 1995-1999. Analytical and nutritional implications

A survey of the total content of trans-18:1 acids and their detailed profile in French food lipids was conducted in 1995-1996, and 1999. For this purpose, 37 food items were chosen from their label indicating the presence of partially hydrogenated vegetable oils (PHVO) in their ingredients. The content as well as the detailed profile of these isomers was established by a combination of argentation thin-layer chromatography and gas liquid chromatography (GLC) on long polar capillary columns. With regard to the mean trans-18:1 acid contents of extracted PHVO, a significant decrease was observed between the two periods, i.e., from 26.9 to 11.8% of total fatty acids. However, only minor differences were noted in the mean relative distribution profiles of individual trans-18:1 isomers with ethylenic bonds between positions delta4 and delta16 for the two periods. The predominant isomer was delta9-18:1 (elaidic) acid, in the wide range 15.2-46.1% (mean, 27.9+/-7.2%) of total trans-18:1 acids, with the delta10 isomer ranked second, with a mean of 21.3% (range, 11.6 to 27.4%). The content of the unresolved delta6 to delta8 isomer group was higher than the delta11 isomer (vaccenic acid), representing on average 17.5 and 13.3%, respectively. Other isomers delta4, delta5, delta12, delta13/delta14, delta15, and delta16, were less than 10% each: 1.0, 1.6, 7.4, 7.1, 1.8, and 1.0%, respectively. However, considering individual food items, it was noted that none of the extracted PHVO were identical to one another, indicating a considerable diversity of such fats available to the food industry. A comparison of data for French foods with similar data recently established for Germany indicates that no gross differences occur in PHVO used by food industries in both countries. Estimates for the absolute mean consumption of individual isomers from ruminant fats and PHVO are made for the French population and compared to similarly reconstructed hypothetical profiles for Germany and North America. Differences occur in the total intake of trans-18:1 acids, but most important, in individual trans-18:1 isomer intake, with a particular increase of the delta6-delta8 to delta10 isomers with increasing consumption of PHVO. It is inferred from the present and earlier data that direct GLC of fatty acids is a faulty procedure that results (i) in variable underestimates of total trans-18:1 acids, (ii) in a loss of information as regards the assessment of individual isomeric trans-18:1 acids, and (iii) in the impossibility of comparing data obtained from human tissues if the relative contribution of dietary PHVO and ruminant fats is not known.

Quantitative analysis of long-chain trans-monoenes originating from hydrogenated marine oil

Gas chromatography (GC) is used for the analysis of trans-fatty acids in partially hydrogenated vegetable oils. Although trans-isomers of C18 carbon length predominate in partially hydrogenated vegetable oils, trans-isomers of C20 and C22 carbon length occur in partially hydrogenated fish oil. We report a simple silver ion chromatographic combined with capillary GC technique for quantitative analysis of trans-monoenes derived from partially hydrogenated fish oil. Silver nitrate thin-layer chromatographic (TLC) plates are developed in toluene/hexane (50:50, vol/vol). Fatty acid methyl esters are separated into saturates (Rf 0.79), trans-monoenes (Rf 0.49), cis-monoenes (Rf 0.27), dienes (Rf 0.10), and polyunsaturated fatty acids with three or more double bonds remaining at the origin. The isolated trans-monoenes are quantitatively analyzed by capillary GC. The technique of argentation TLC with GC analysis of isolated methyl esters is highly reproducible with 4.8% variation (i.e., coefficient of variation, CV%) in R. values and 4.3 and 6.9% CV% in quantification within batch and between batch, respectively. Furthermore, the combined technique revealed that direct GC analysis underestimated the trans-content of margarines by at least 30%. In this study, C20 and C22 trans-monoenes were found in relatively large quantities; 13.9% (range 10.3-19.6%) and 7.5% (range 5.3-11.5%), respectively, in margarine purchased in 1995, but these C20 and C22 trans-monoenes were much reduced (0.1%) in a fresh selection of margarine purchased in 1998. Compositional data from labels underestimated the trans-content of margarines, especially those derived from hydrogenated marine oil. Low levels of C20 transmonoenes (range 0.1-0.3%) and C22 trans-monoenes (range 0.0-0.1%) were identified in adipose tissue obtained from healthy volunteers in 1995, presumably indicating consumption of partially hydrogenated fish oil.

Trans fatty acids in adipose tissue of French women in relation to their dietary sources

This study reports the fatty acid composition of subcutaneous adipose tissue in French women with special emphasis on the content of trans fatty acids originating from two main dietary sources, ruminant fats and partially hydrogenated vegetable oils (PHVO). Adipose tissue trans fatty acid levels from 71 women, recruited between 1997 and 1998, were determined using a combination of capillary gas chromatography and silver nitrate thin-layer chromatography. Results indicate that on average cis monounsaturates accounted for 47.9% of total fatty acids, saturates for 32.2%, and linoleic acid for 14.4%. Cis n-3 polyunsaturates represented only 0.7%. Total content of trans fatty acids was 2.32 +/- 0.50%, consisting of trans 18:1 (1.97 +/- 0.49%), trans 18:2 (0.28 +/- 0.08%), and trans 16:1 (0.06 +/- 0.03%). Trans 18:3 isomers were not detectable. The level of trans fatty acids found in adipose tissue of French women was lower than those reported for Canada, the United States, and Northern European countries but higher than that determined in Spain. Therefore, trans fatty acid consumption in France appears to be intermediate between that of the United States or North Europe and that of Spain. Based on the equation of Enig et al., we estimated the mean daily trans 18:1 acid intake of French women at 1.9 g per person. The major trans 18:1 isomer in adipose tissue was delta11 trans, as in ruminant fats. Estimates of relative contribution of trans fatty acid intake were 55% from ruminant fats and 45% from PHVO. This pattern contrasts sharply with those established for Canada and the United States where PHVO is reported to be the major dietary source of trans fatty acids.

Inhibitory effect of linoleic acid on chain elongation and desaturation of 18:2 c,t isomers in lactating and neonatal rats

The previous studies showed that dietary 18:2 c,t isomers could be chain-elongated and desaturated to produce unusual 20:4 isomers. The present study was undertaken to determine the minimal amount of 18:2n-6 required to suppress the chain elongation and desaturation of 18:2 c,t isomers in the lactating and neonatal rats when animals were fed 15% partially hydrogenated canola oil diet containing 1.72% energy as 18:2 c,t isomers and varying amounts of free 18:2n-6. These diets induced marginal essential fatty acid (EFA) deficiency states (0.56% energy 18:2n-6) to EFA adequacy (2.56% energy 18:2n-6). After feeding for 50 d, the female animals were mated with males by overnight pairing. After conception, the lactating rats were killed, together with one pup from each dam, at term and day 26 of lactation. Two unusual 20:4 isomers in both maternal and neonatal liver phospholipids were identified as 20:4delta5c,8c,11c,14t and 20:4delta5c,8c,11c,15t, which were derived from 18:2delta9c,12t and 18:2delta9c,13t, respectively. The results showed that 18:2n-6 at about 2.0% of total energy in maternal diet was required to block the production of 20:4delta5c,8c,11c,14t and 20:4delta5c,8c,11c,15t in the maternal liver, whereas 18:2n-6 at about 2.5% of total energy in maternal diet was required to suppress production of these unusual 20:4 isomers in the neonatal liver.

Rapid determination of trans-fatty acids in human adipose tissue. Comparison of attenuated total reflection infrared spectroscopy and gas chromatography

A rapid attenuated total reflection (ATR) infrared (IR) spectroscopy procedure was used for quantitating the levels of total trans-fatty acid methyl ester (FAME) derivatives in neat (without solvent) test samples isolated from human adipose tissue. This procedure requires no weighing of the laboratory sample. The single-beam spectrum of the trans-containing FAMEs was 'ratioed' against that of a reference material having only cis double bonds in order to obtain a symmetric absorption band at 966 cm(-1) on a horizontal background. A single-reflection ATR diamond cell that requires only about 1 microl of neat FAMEs was used. The average level of trans-fatty acids in human adipose tissue found by ATR (3.07+/-0.27%) was generally higher than that obtained by gas chromatography (2.59+/-0.20%). Reasons for such a difference are discussed.

Trans, n-3, and n-6 fatty acids in Canadian human milk

The presence of trans fatty acids in human milk may be a concern because of their possible adverse nutritional and physiological effects on the recipient infant. The mother's diet is the source of human milk trans fatty acids, and since these fatty acids are prevalent in many common foods of the Canadian diet, the trans fatty acid content and the fatty acid composition of Canadian human milk were measured by gas-liquid chromatography coupled with silver nitrate-thin layer chromatography. In samples obtained from 198 lactating mothers across Canada, the average percentage of total trans (sum of t18:1, t18:2, and t18:3) was 7.2% of breast milk fatty acids with a range of 0.1-17.2%. Analysis of t18:1 isomer distribution indicated that partially hydrogenated vegetable oils are the major source of these trans fatty acids in human milk, whereas contribution from dairy products appeared to be relatively minor. Linoleic and alpha-linolenic acid levels were inversely related to the total trans fatty acids, indicating that the elevation of trans fatty acids in Canadian human milk is at the expense of n-3 and n-6 essential fatty acids. Levels of arachidonic and docosahexaenoic acids did not correlate with their parent fatty acids, indicating that it might be difficult to elevate the levels of n-6 and n-3 c20-22 polyunsaturated fatty acids in breast milk by increasing levels of linoleic and alpha-linolenic acids in the mother's diet.

In vivo 13C nuclear magnetic resonance: applications and current limitations for noninvasive assessment of fatty acid status

As a noninvasive method, in vivo 13C nuclear magnetic resonance has potentially important applications in understanding the metabolism of long chain fatty acids in organs of living humans. At present, this methodology is most advanced for research on glucose utilization. However, the main 13C signals visible in vivo are from fatty acids in adipose tissue and the olefinic signals can be used to noninvasively estimate adipose tissue content and relative dietary intake of polyunsaturates and monounsaturates. The low natural abundance of 13C improves the utility of this isotope for fatty acid tracer studies. Due to excessive signal broadening, uniform 13C-labelling seems to have limited application in in vivo fatty acid studies. Tracer fatty acids with 13C enrichment at a specific carbon position, i.e., [13-13C] gamma-linolenate, appear to be the most useful for in vivo tracer studies. Development of methods permitting resolution of 13C enrichment in structural lipids of lean tissues will be an important breakthrough which may make human tracer studies feasible and worthwhile.