Isomeric fatty acids: Evaluating status and implications for maternal and child health

“Isomeric fatty acids” is a term that refers to the trans- and positional isomers formed during hydrogenation of naturally occurring oils. The purposes of this paper are as follows: (i) to summarize potential exposure of infants to isomeric fatty acids by reviewing estimates of isomeric fatty acids in the maternal diet, in human milk, and in infant formula/infant foods, and (ii) to evaluate the evidence for adverse effects of isomeric fatty acids on infant development with respect to growth and essential fatty acid status. Estimates of the intake of trans-fatty acids vary widely both within and across populations. Current estimates of trans-fatty acids in the North American population are 4–11% of total fatty acids or 3–13 g/(person·d), whereas in Mediterranean countries in which olive oil is the primary fat and in Far Eastern countries in which little commercially hydrogenated fat is consumed, per capita consumption of trans-fatty acids is <1–2 g/d. The trans-fatty acid content of human milk reflects the cross-cultural variation in the maternal diet, with trans-fatty acids in human milk samples ranging from 6 to 7% in North America to <0.5% in Hong Kong. Trans-fatty acids are transferred from the maternal diet through the placenta to the developing fetus or through milk to the breast-fed infant. In some studies, plasma trans-fatty acids are inversely related to birth weight and head circumference. The hypothesis that dietary trans-fatty acids could inhibit biosynthesis of long-chain polyunsaturated fatty acids with 20 and 22 carbon atoms and thus affect infant development is supported by studies demonstrating an inverse correlation of plasma trans-fatty acids with n−3 and n−6 long-chain polyunsaturated fatty acids in infants. However, no such relationship has been observed in human milk. A definitive answer concerning a potentially adverse effect of dietary trans-fatty acids on infant development awaits future studies.     

Comparison of body weight and adipose tissue in male C57BI/6J mice fed diets with and withouttrans fatty acids

The effect of a diet containingtrans-fatty acids (tFA) on the fatty acid composition and fat accumulation in adipose tissue was investigated in mice. Male C57BI/6J mice were fed Control or Trans Diets that were similar, except that 50% of the 18∶1, which was allcis in the Control Diet, was replaced bytFA in the Trans Diet. At selected ages, body weight, epididymal fat pad weight, perirenal fat yield, adipose tissue cellularity and fatty acid composition were examined. Over the time period studied (2–24 mon), the proportion of 18∶0 and 16∶0 tended to decrease whilecis-18∶1 levels increased. Compared to the Control Diet, the Trans Diet resulted in adipose tissue lipids with higher percentages of 14∶0 and 18∶2n−6 and lower percentages ofcis-18∶1 and 20∶4n−6. In polar lipids,tFA replaced saturated fatty acids, whereastFA replacedcis-18∶1 in the nonpolar lipids. Body weights at 16 and 24 mon of age and epididymal fat pad weights at 8–24 mon of age were lower in mice fed the Trans Diet as compared to those fed the Control Diet. At the ages studied, the Trans Diet also resulted in lower values for perirenal fat weights, triacylglycerol to polar lipid ratios, and adipose cell size. The data suggest that chronic consumption oftFA affects lipid metabolism and results in decreased fat accumulation in murine adipose tissue.     

Impact of Administered <Emphasis Type="Italic">Bifidobacterium</Emphasis> on Murine Host Fatty Acid Composition

Recently, we reported that administration of Bifidobacteria resulted in increased concentrations of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in murine adipose tissue [1]. The objective of this study was to assess the impact of co-administration of Bifidobacterium breve NCIMB 702258 and the substrate for EPA, α-linolenic acid, on host fatty acid composition. α-Linolenic acid-supplemented diets (1%, wt/wt) were fed to mice (n = 8), with or without B. breve NCIMB 702258 (daily dose of 10⁹ microorganisms) for 8 weeks. Two further groups received either supplement of B. breve alone or unsupplemented diet. Tissue fatty acid composition was assessed by gas liquid chromatography. Dietary supplementation of α-linolenic acid resulted in higher (P < 0.05) α-linolenic acid and EPA concentrations in liver and adipose tissue and lower (P < 0.05) arachidonic acid in liver, adipose tissue and brain compared with mice that did not receive α-linolenic acid. Supplementation with B. breve NCIMB 702258 in combination with α-linolenic acid resulted in elevated (P < 0.05) liver EPA concentrations compared with α-linolenic acid supplementation alone. Furthermore, the former group had higher (P < 0.05) DHA in brain compared with the latter group. These results suggest a role for interactions between fatty acids and commensals in the gastrointestinal tract. This interaction between administered microbes and fatty acids could result in a highly effective nutritional approach to the therapy of a variety of inflammatory and neurodegenerative conditions.     

Preparative Separation of <Emphasis Type="Italic">cis</Emphasis>- and <Emphasis Type="Italic">trans</Emphasis>-Isomers of Unsaturated Fatty Acid Methyl Esters Contained in Edible Oils by Reversed-Phase High-Performance Liquid Chromatography

In order to measure exactly the trans-fatty acids content in food materials, a preparative group separation of cis- and trans-isomers of unsaturated fatty acid methyl esters (FAMEs) was achieved by an isocratic reversed-phase HPLC (RP-HPLC) method. The trans-isomers of 16:1, 18:1, 18:2, 18:3, 20:1 and 22:1 FAMEs were readily separated from the corresponding cis-isomers by a COSMOSIL Cholester C18 column (4.6 mm I.D. × 250 mm, Nacalai Tesque) or a TSKgel ODS-100Z column (4.6 mm I.D. × 250 mm, TOSOH), using acetonitrile as the mobile phase. This method was applied for determining the trans-18:1 fatty acid content in partially hydrogenated rapeseed oil. The methyl esters of cis- and trans-18:1 isomers of the oil were collected as two separate fractions by the developed RP-HPLC method. Each fraction was analyzed by gas chromatography (GC) for both qualitative and quantitative information on its positional isomers. By a combination of RP-HPLC and GC methods, a nearly complete separation of cis- and trans-18:1 positional isomers was achieved and the trans-18:1 fatty acid content was able to be evaluated more precisely than is possible by the direct GC method. The reproducibility of cis- and trans-18:1 isomers fractionated by the RP-HPLC method was better than 98%. These results suggested that the preparative RP-HPLC method developed in this study could be a powerful tool for trans-fatty acid analysis in edible oils and food products as an alternative to silver-ion chromatography.     

Conjugated Linoleic Acid Isomers, t10c12 and c9t11, are Differentially Incorporated into Adipose Tissue and Skeletal Muscle in Humans

Conjugated linoleic acid (CLA) is a popular supplement believed to enhance immune function, body composition and insulin sensitivity, but results of scientific studies investigating its effects are conflicting. The isomer- and tissue-specific effects of CLA may explain these conflicting results. Therefore, this study quantified the incorporation of the c9t11 and t10c12 CLA isomers into adipose tissue and skeletal muscle in response to supplementation in healthy, regularly-exercising, non-obese persons. The CLA group (n = 14) ingested 3.9 g per day CLA (50:50 t9c11:c10t12) and the placebo group (n = 11) 3.9 g per day high-oleic-acid sunflower oil for 12 weeks. Following supplementation, the t10c12 isomer was incorporated into adipose tissue triacylglycerol (P < 0.001), and the c9t11 isomer tended to increase in skeletal muscle phospholipids (P = 0.056). Therefore, human adipose tissue and skeletal muscle are enriched with CLA in an isomer-specific manner.     

Dissimilar Properties of Vaccenic Versus Elaidic Acid in β-Oxidation Activities and Gene Regulation in Rat Liver Cells

Vaccenic acid (trans-11-C_18:1) chemically resembles elaidic acid (trans-9-C_18:1) which is assumed to increase the risk of cardiovascular diseases, and thus could exert similar effects. Possible different oxidation rates of vaccenic versus elaidic acid were checked in muscles and liver, and through related gene expression in normal rat liver cells. In hepatic mitochondria, carnitine palmitoyltransferase (CPT) I exhibited comparable activity rates with both trans-isomers. CPT II activity was 30% greater (P < 0.05) with vaccenic than with elaidic acid as nonesterified fatty acids (NEFAs) or acyl-CoAs. Activity of the first β-oxidation step was similar between the isomers in all the tissue slices and liver extracts assayed. Respiration rates were comparable with both trans-isomers as NEFAs in various liver extracts, but were 30% greater (P < 0.05) with vaccenoyl-CoA than with elaidoyl-CoA in liver mitochondria. Vaccenic acid was oxidised 25% more (P < 0.05) by liver peroxisomes than elaidic acid. In hepatocytes cultured with trans- and corresponding cis-C_18:1 isomers, gene expression of CPT I, hydroxyacyl-CoA dehydrogenase and hydroxymethylglutaryl-CoA synthase was at least 100% increased (P < 0.05), but was unchanged with vaccenic acid, relative to controls. In conclusion, the position and geometry of the double bonds in acyl chains are suggested to confer on vaccenic and elaidic acid specific biochemical properties that might differently affect their fates in tissues.     

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 Δ11trans, 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.     

Effects oftrans fatty acids on lipid accumulation in 3T3-L1 cells

Previous work had shown that dietarytrans fatty acids (tFA) resulted in decreased fat deposition in adipose tissue. This study was conducted to see iftFA influence lipid accumulation in Swiss mouse fibroblast 3T3-L1 cells, which are widely used as an adipocyte model. Cells were cultured in the presence of experimental or control growth media supplemented with fatty acids complexed to bovine serum albumin. Fatty acid compositions of experimental and control growth media were similar except that the octadecenoates in the control growth media werecis fatty acids, whereas those in the experimental media contained bothcis andtrans fatty acids. Cell-conditioned media and cellular lipids at the preadipocyte and differentiating adipocyte stages were analyzed. At both stages of development, less fat accumulated, in cells cultured in the presence oftFA, due primarily to a decrease in the nonpolar lipid content of cells exposed totFA, and linoleate to arachidonate ratios were higher in cells supplemented withtFA. Calculations comparing sums of saturated and monounsaturated fatty acids in cells at the differentiating adipocyte stage suggested thattFA may have replaced monoun-saturated fatty acids in the nonpolar lipid fraction and saturated fatty acids in the polar lipid fraction. The results of these studies are in good agreement with thein vivo effects oftFA seen in previous work with mouse adipose tissue. It was concluded that the 3T3-L1in vitro model is an appropriate system for further studies oftFA and lipid metabolism in adipose tissue.     

Maternal Consumption of trans-Fatty Acids During the First Half of Gestation are Metabolically Available to Suckled Newborn Rats

Dietary trans-fatty acids (t-FA) during pregnancy have adverse effects on growth and development. To determine the effect of dietary t-FA during just the first half of pregnancy, rats were given a diet containing 8 % hydrogenated peanut oil and 2 % olive oil (PO) and compared to rats given a diet containing 10 % olive oil (OO). After 12 days all rats were fed standard diet and were studied at days 12 or 20 of pregnancy or days 1 or 6 postpartum. At day 12 of pregnancy there were small differences in the plasma and lumbar adipose tissue fatty acid profiles and elaidic acid [18:1(n-9)t] was present in the PO group. From day 12 to 20 of pregnancy, plasma non-esterified fatty acids, glycerol, triacylglycerols (TAG) and most individual fatty acids increased more in PO than in OO. At day 20 of pregnancy in the PO group most plasma elaidic acid appeared as plasma TAG and was also present in the mammary gland, to decline in both sites at day 1 postpartum. Elaidic acid concentration was low in the plasma of 20-day fetuses, increased in 1-day newborns declining at day 6. Thus t-FA, eaten during early pregnancy, accumulated in maternal adipose tissue and were released during late pregnancy to be taken up by the mammary gland becoming available to the newborns during suckling.     

Effect of <Emphasis Type="Italic">trans</Emphasis>8, <Emphasis Type="Italic">cis</Emphasis>10+<Emphasis Type="Italic">cis</Emphasis>9, <Emphasis Type="Italic">trans</Emphasis>11 Conjugated Linoleic Acid Mixture on Lipid Metabolism in 3T3-L1 Cells

Evidence suggests that minor isomers of conjugated linoleic acid (CLA), such as trans8, cis10 CLA, can elicit unique biological effects of their own. In order to determine the effect of a mixture of t8, c10+c9, t11 CLA isomers on selected aspects of lipid metabolism, 3T3-L1 preadipocytes were differentiated for 8 days in the presence of 100 μM linoleic acid (LA); t8, c10+c9, t11 CLA; t10, c12+c9, t11 CLA or purified c9, t11 CLA. Whereas supplementation with c9, t11 and t10, c12+c9, t11 CLA resulted in cellular triglyceride (TG) concentrations of 3.4 ± 0.26 and 1.3 ± 0.11 μg TG/μg protein, respectively (P < 0.05), TG accumulation following treatment with CLA mixture t8, c10+c9, t11 was significantly intermediate (2.5 ± 0.22 μg TG/μg protein, P < 0.05) between the two other CLA treatments. However, these effects were not attributable to an alteration of the Δ⁹ desaturation index. Adiponectin content of adipocytes treated with t8, c10+c9, t11 mixture was similar to the individual isomer c9, t11 CLA, and both the t8, c10+c9, t11 and c9, t11 CLA groups were greater (P < 0.05) than in the t10, c12+c9, t11 CLA group. Overall, these results suggest that t8, c10+c9, t11 CLA mixture affects TG accumulation in 3T3-L1 cells differently from the c9, t11 and t10, c12 isomers. Furthermore, the reductions in TG accumulation occur without adversely affecting the adiponectin content of these cells.     

Body Compositional Changes and Growth Alteration in Chicks from Hens Fed Conjugated Linoleic Acid

Effects of feeding conjugated linoleic acid (CLA) to hens on progeny chick development and composition at hatch (NHC) and three weeks of age (TWC) were assessed. CLA (0 or 0.5%, composed of mixed isomers of cis-9,trans-11 or trans-10,cis-12-CLA) was fed to hens with either safflower (SO) or olive oil (OO) (3 or 3.5%) to assure successful hatch for 2 weeks prior to collection for incubation. Maternal CLA feeding had no effect on hatchability, but improved egg fertility (p < 0.05). Maternal feeding of CLA with SO increased 21 day-old progeny growth, while CLA with OO decreased growth (oil*CLA, p < 0.05). In 25 day-old chicks (TWC), but not NHC, maternal CLA decreased the proportion of total body water (p < 0.05) and increased body ash (p < 0.05). While monounsaturated fatty acids were decreased and saturated fatty acids increased in eggs and NHC from hens fed CLA, no differences in fatty acid composition were observed in chicks at 25 days of age from hens fed CLA. Maternal CLA feeding resulted in the presence of c9,t11 and t10,c12-CLA in NHC, but only c9,t11 in the TWC. In conclusion, hens fed CLA led to improved fertility and altered body composition at 3 weeks of age.     

Inclusion of Flaxseed in Hay- and Barley Silage Diets Increases Alpha-Linolenic Acid in Cow Plasma Independent of Forage Type

Feeding flaxseed to cattle may be a means of increasing omega-3 fatty acid levels in ruminant products, but possible interactions with conserved forages have not been investigated. Twelve Holstein cows were used in a replicated 4 × 4 Latin Square experiment. Cows were fed one of four 50:50 forage:concentrate diets (DM basis): hay (hay control, HC), hay plus 15% ground flaxseed (hay-flaxseed, HF), barley silage (silage control, SC), and barley silage plus 15% ground flaxseed (silage-flaxseed, SF). Plasma concentrations of alpha-linolenic acid (ALA) did not differ between SC and HC diets. Flaxseed increased ALA (P < 0.05), but levels were not influenced by forage type. Flaxseed slightly increased 18:2n-6 (P < 0.05) and some n-6 and n-3 elongation and desaturation products, particularly arachidonic acid (ARA) and eicosapentaenoic acid (EPA). Flaxseed also increased C18:0 (P < 0.05) with this increase being greater (P < 0.01) for cows fed SF than HF. Feeding flaxseed also increased plasma C18:1-trans isomers (P < 0.01), predominantly vaccenic acid (VAA, 18:1-t11), with this increase being greater (P < 0.05) in cows fed HF than SF. Although conjugated linoleic acid (CLA) was increased (P < 0.001) with flaxseed it was not influenced by forage type (P = 0.06). Overall, feeding flaxseed increased plasma ALA, EPA, ARA and CLA independently of forage type. Feeding flaxseed with silage, however, resulted in more 18:0, while feeding flaxseed with hay resulted in greater accumulations of plasma 18:1-trans isomers mainly in the form of VAA.     

Conjugated Linoleic Acid (t-10, c-12) Reduces Fatty Acid Synthesis de Novo, but not Expression of Genes for Lipid Metabolism in Bovine Adipose Tissue ex Vivo

We hypothesized that exogenous fatty acids, and especially or 18:2 trans-10, cis-12 conjugated linoleic acid (CLA), would decrease adipogenic and lipogenic gene expression and de novo fatty acid biosynthesis in intramuscular (i.m.) and subcutaneous (s.c.) adipose tissues. Fresh i.m. and s.c. adipose tissues were collected from the longissimus thoracis muscle of Angus steers at 12, 14, and 16 months of age (n = 4 per time point). Adipose tissue explants were incubated in duplicate for 48 h with 40 μM α-linolenic (ALA), oleic, stearic, trans-vaccenic, or CLA. Adipocyte size, acetate and glucose incorporation into fatty acids in vitro and mRNA levels for C/EBPβ, CPT1β, GPR43, PPARγ, PRKAA1 (AMPKα) and SCD1 were measured following the incubations. PRKAA1 and SCD1gene expression were greater (P < 0.001) in s.c. adipose tissue than in i.m. adipose tissue and acetate incorporation into lipids and C/EBPβ, PPARγ, and SCD1gene expression were greater at 16 months of age than at 12 months of age in i.m. adipose (P < 0.01). C/EBPβ gene expression increased by 16 months of age and PRKAA1 gene expression decreased by 16 months of age in s.c. adipose tissue. All fatty acids increased s.c. adipocyte volumes whereas CLA decreased acetate incorporation into lipids in s.c. adipose tissue (P < 0.05), but none of the fatty acids affected gene expression in i.m. or s.c. adipose tissue (P > 0.10). Thus, CLA depressed de novo fatty acid biosynthesis from acetate but neither CLA nor other fatty acids significantly affected adipogenic or lipogenic gene expression.     

Effect of ALA-Enriched Food Supply on Cardiovascular Risk Factors in Males

The outcome of a total dietary approach using a wide range of n-3 polyunsaturated fatty acids (PUFA) enriched food items on cardiovascular diseases called for further investigation. The study objective was to assess the effect of an ALA-enriched food supply on cardiovascular risk factors in healthy males. A dietary intervention (single-blind field trial with pre- and post-measurements) was performed with 59 healthy males in a Belgian prison. Over a period of 12 weeks they were supplied with an n-3 enriched diet (containing 6.5 g n-3 PUFA/day compared to 4 g n-3 PUFA/day in the standard diet) that was substituted for their regular diet, increasing mainly the α-linolenic acid intake (from 2.8 to around 5 g/day). The results indicated no impact on subjects waist circumference, weight and BMI or systolic blood pressure. In contrast, the diastolic blood pressure significantly decreased during the intervention period (from 74.6 ± 8.2 to 71.7 ± 10.1 mmHg; P < 0.02). Moreover, the HDL-cholesterol level increased in non-smoking participants (from 0.97 ± 0.25 to 1.06 ± 0.23 mmol/l; P < 0.03). In summary, the study demonstrated that enrichment of commonly eaten food items with n-3 fatty acids provides the opportunity to increase the n-3 fatty acid intake and to decrease the n-6/n-3 ratio which results in a decreasing diastolic blood pressure and an increase of HDL-cholesterol (in non-smokers). An erratum to this article can be found at     

Divergent incorporation of dietary trans fatty acids in different serum lipid fractions

Trans fatty acids may be involved in atherosclerotic vascular diseases. We investigated the incorporation of dietary trans fatty acids and oleic acid into the serum triglycerides (TG), cholesterol esters (CE), and phospholipids (PL). Fourteen healthy female volunteers, aged 23.2±3.1 yr (mean±SD), body mass index 20.8±2.1 kg/m² participated in this study. All subjects consumed both a trans fatty acid-enriched diet (TRANS diet) and an oleic acid-enriched diet (OLEIC diet) for 4 wk according to a randomized crossover design. Both experimental diet periods were preceded by consumption of a baseline diet for 2 wk which supplied 37% of total energy (E%) as fat: 18 E% from saturated fatty acids (SFA), 12 E% from monounsaturated fatty acids, and 6 E% from polyunsaturated fatty acids. Five E% of the SFA in the baseline diet was replaced by trans fatty acids (18∶1 t and 18∶2 c,t+18∶2t,t, where c is cis and t is trans) in the TRANS diet and by oleic acid (18∶1n-9) in the OLEIC diet. After the TRANS diet, the proportions of 18∶1t and 18∶2t increased (P <0.001) in all serum lipid fractions analyzed. The increase of 18∶1 t in TG and PL (1.80±0.28 vs. 5.26±1.40; 1.07±0.34 vs. 3.39±0.76 mol% of total fatty acids, respectively) was markedly higher than that in CE (0.44±0.07 vs. 0.92±0.26), whereas that of 18∶2t was nearly the same in all three fractions. The proportions of palmitic, stearic, arachidonic, and eicosapentaenoic acids in TG, CE, and PL and that of oleic acid in TG and CE were decreased when compared with the baseline value. In contrast, the proportion of palmitoleic acid in TG and PL and that of linoleic acid in PL increased on the TRANS diet. After consumption of the OLEIC diet, the proportion of oleic acid increased in all three lipid fractions analyzed, and the percentage increase was nearly the same in all fractions. In contrast, the proportions of 18∶1 t in TG and PL and 18∶2 t in TG and CE decreased when compared with the baseline value. In conclusion, a moderate increase in dietary trans fatty acids resulted in a marked incorporation into serum lipids and decreased the conversion of linoleic acid to its more unsaturated long-chain metabolites. Analysis of 18∶1 t from serum TG and PL seems to reflect reliably the dietary intake of this fatty acid.     

<Emphasis Type="Italic">Trans</Emphasis> Fatty Acids in Human Milk are an Indicator of Different Maternal Dietary Sources Containing <Emphasis Type="Italic">Trans</Emphasis> Fatty Acids

The trans fatty acid (TFA) patterns in the fats of ruminant meat and dairy products differ from those found in other (processed) fats. We have evaluated different TFA isomers in human breast milk as an indicator of dietary intake of ruminant and dairy fats of different origins. Breast milk samples were collected 1 month postpartum from 310 mothers participating in the KOALA Birth Cohort Study (The Netherlands). The study participants had different lifestyles and consumed different amounts of dairy products. Fatty acid methyl esters were determined by GC-FID and the data were evaluated by principal component analysis (PCA), ANOVA/Post Hoc test and linear regression analysis. The two major principal components were (1) 18:1 trans-isomers and (2) markers of dairy fat including 15:0, 17:0, 11(trans)18:1 and 9(cis),11(trans)18:2 (CLA). Despite similar total TFA values, the 9(trans)18:1/11(trans)18:1-ratio and the 10(trans)18:1/11(trans)18:1-ratio were significantly lower in milk from mothers with high dairy fat intake (40–76 g/day: 0.91 ± 0.48, P < 0.05) compared to low dairy fat intake (0–10 g/day: 1.59 ± 0.48), and lower with strict organic meat and dairy use (>90% organic: 0.92 ± 0.46, P < 0.05) compared to conventional origin of meat and dairy (1.40 ± 0.61). Similar results were obtained for the 10(trans)18:1/11(trans)18:1-ratio. We conclude that both ratios are indicators of different intake of TFA from ruminant and dairy origin relative to other (including industrial) sources.     

<Emphasis Type="Italic">Trans</Emphasis>–<Emphasis Type="Italic">trans</Emphasis> Conjugated Linoleic Acid Enriched Soybean Oil Reduces Fatty Liver and Lowers Serum Cholesterol in Obese Zucker Rats

Conjugated linoleic acid (CLA) is a collection of octadecadienoic fatty acids that have been shown to possess numerous health benefits. The CLA used in our study was produced by the photoisomerization of soybean oil and consists of about 20% CLA; this CLA consists of 75% trans–trans (a mixture of t8,t10; t9,t11; t10,t12) isomers. This method could be readily used to increase the CLA content of all soybean oil used as a food ingredient. The objective of this study was to determine the effects of trans–trans CLA-rich soy oil, fed as a dietary supplement, on body composition, dyslipidemia, hepatic steatosis, and markers of glucose control and liver function of obese fa/fa Zucker rats. The trans–trans CLA-rich soy oil lowered the serum cholesterol and low density lipoprotein–cholesterol levels by 41 and 50%, respectively, when compared to obese controls. Trans–trans CLA-rich soy oil supplementation also lowered the liver lipid content significantly (P < 0.05) with a concomitant decrease in the liver weight in the obese rats. In addition, glycated hemoglobin values were improved in the group receiving CLA-enriched soybean oil in comparison to the obese control. PPAR-γ expression in white adipose tissue was unchanged. In conclusion, trans–trans CLA-rich soy oil was effective in lowering total liver lipids and serum cholesterol.     

Anin vivo 13C magnetic resonance spectroscopic study of the relationship between diet and adipose tissue composition

¹³C magnetic resonance spectroscopy (MRS) is a noninvasive technique used in the study of lipids. We applied¹³C MRS to assess the effects of long-term dietary variation on adipose tissue composition in humans.In vivo ¹³C MRS was used to analyze the fatty acid composition of adipose tissue in 88 healthy volunteers with significantly different diets (38 vegans, 11 vegetarians, and 39 omnivores) assessed by analysis of dietary records. Results were compared with the serum lipid profile.¹³C MRS revealed clear differences in the adipose tissue composition of vegans, which contained more unsaturated (P<0.01) and fewer saturated fatty acids (P<0.01) compared with omnivores and vegetarians. The vegan subjects had a significantly lower intake of saturated fatty acids and higher intake of polyunsaturated fatty acids than either the omnivore or the vegetarian groups (P<0.01). These findings were associated with significantly lower levels of serum total cholesterol and low density lipoprotein-cholesterol in the vegan group compared with the omnivores. Our results demonstrate the use of¹³C MRS for the noninvasive study of adipose tissue composition and its application to the study of the interaction between long-term dietary and metabolic risk factors in humans.     

Noninvasive characterization of neonatal adipose tissue by 13C magnetic resonance spectroscopy

In vivo ¹³C magnetic resonance spectroscopy (MRS) was applied noninvasively to analyze the fatty acid composition of adipose tissue in 21 full-term newborn infants and 6 mothers. In order to assess the effects of gestational and postnatal age on adipose tissue composition, we studied preterm infants at birth, term infants at the ages of 6 wk and at 6 mon. We also investigated the influence of maternal diet on infant adipose tissue composition by studying the breast-fed infants of women who maintained either an omnivore or a vegan diet. Significant differences were observed in adipose tissue composition of neonates compared with their mothers. Neonates had more saturated and less unsaturated fatty acids than their mothers (P<0.01). We also observed changes in adipose tissue composition with maturity. From birth to 6 wk of age ¹³C MR spectra showed a significant increase in the amount of unsaturated fatty acids, particularly polyunsaturated fatty acids (P<0.01). Similarly, differences were seen as a result of gestational age. Preterm infants had relatively fewer unsaturated fatty acids than full-term infants. A greater proportion of these unsaturated fatty acids were polyunsaturated. Our results demonstrate that ¹³C MRS can be utilized to assess noninvasively neonatal adipose tissue lipid composition and to monitor the effects of developmental changes due to gestational age and oral feeding.     

Influence of Interesterification of a Stearic Acid-Rich Spreadable Fat on Acute Metabolic Risk Factors

Chemical and enzymatic interesterification are used to create spreadable fats. However, a comparison between the two processes in terms of their acute metabolic effects has not yet been investigated. A randomised crossover study in obese (plasma TAG > 1.69 mmol/L, and BMI > 30 (BMI = kg/m²) or waist circumference > 102 cm, n = 11, age = 59.3 ± 1.8 years) and non-obese (plasma triacylglycerol (TAG) < 1.69 mmol/L, and BMI < 30  or waist circumference < 102 cm, n = 10, age = 55.8 ± 2.2 years) men was undertaken to compare the effects of chemical versus enzymatic interesterification on postprandial risk factors for type 2 diabetes (T2D) and cardiovascular disease (CVD). TAG, cholesterol, glucose, insulin and free fatty acid concentrations were measured for 6 h following consumption of 1 g fat/kg body mass of non-interesterified (NIE), chemically interesterified (CIE), enzymatically interesterified (EIE) stearic acid-rich fat spread or no fat, each with 50 g available carbohydrate from white bread. Interesterification did not affect postprandial glucose, insulin, free fatty acids or cholesterol (P > 0.05). Following ingestion of NIE, increases in serum oleic acid were observed, whereas both oleic and stearic acids were increased with CIE and EIE (P < 0.05). While postprandial TAG concentrations in non-obese subjects were not affected by fat treatment (P > 0.05), obese subjects had an 85% increase in TAGs with CIE versus NIE (P < 0.05). The differences in TAG response between non-obese and obese subjects suggest that interesterification may affect healthy individuals differently compared to those already at risk for T2D and/or CVD.