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PubMed1999

Trans fatty acid isomers in human health and in the food industry.

Trans fatty acids are unsaturated fatty acids with at least one double bond in the trans configuration. These fatty acids occur naturally in dairy and other natural fats and in some plants. However, industrial hydrogenation of vegetable or marine oils is largely the main source of trans fatty acids in our diet. The metabolic effect of trans isomers are today a matter of controversy generating diverse extreme positions in light of biochemical, nutritional, and epidemiological studies. Trans fatty acids also have been implicated in the etiology of various metabolic and functional disorders, but the main concern about its health effects arose because the structural similarity of these isomers to saturated fatty acids, the lack of specific metabolic functions, and its competition with essential fatty acids. The ingestion of trans fatty acids increases low density lipoprotein (LDL) to a degree similar to that of saturated fats, but it also reduces high density lipoproteins (HDL), therefore trans isomers are considered more atherogenic than saturated fatty acids. Trans isomers increase lipoprotein(a), a non-dietary-related risk of atherogenesis, to levels higher than the corresponding chain-length saturated fatty acid. There is little evidence that trans fatty acids are related to cancer risk at any of the major cancer sites. Considerable improvement has been obtained with respect to the metabolic effect of trans fatty acids due the development of analytical procedures to evaluate the different isomers in both biological and food samples. The oleochemical food industries have developed several strategies to reduce the trans content of hydrogenated oils, and now margarine and other hydrogenated-derived products containing low trans or virtually zero trans are available and can be obtained in the retail market. The present review provides an outline of the present status of trans fatty acids including origin, analytical procedures, estimated ingestion, metabolic effects, efforts to reduce trans isomers in our diet, and considerations for future prospects on trans isomers.

Dietary Fats↗

PubMed2005

Long-term intake of trans-fatty acids and risk of gallstone disease in men.

BACKGROUND: The consumption of trans-fatty acids adversely affects blood lipid levels. The relationship with the incidence of gallstone disease is unknown. METHODS: We prospectively studied consumption of trans-fatty acids in relation to the risk of gallstone disease in a cohort of 45,912 men. trans-Fatty acid consumption was assessed using a validated semiquantitative food frequency questionnaire. Newly diagnosed gallstone disease, by radiology or cholecystectomy, was ascertained biennially. RESULTS: During 14 years of follow-up, we documented 2356 new cases of symptomatic gallstones. After adjusting for age and other potential risk factors, we found that compared with men in the lowest quintile of dietary intake of trans-fatty acids, the relative risk (RR) of gallstone disease for those in the highest quintile was 1.23 (95% confidence interval [CI], 1.04-1.44; P for trend, .03). Among individual trans-fatty acids, the RR for trans-oleic fatty acid, when extreme quintiles were compared, was 1.24 (95% CI, 1.06-1.45; P for trend, .02). Intakes of trans-palmitoleic fatty acid (RR, 1.09; 95% CI, 0.90-1.31), trans,trans 18:2 fatty acid (RR, 1.14; 95% CI, 0.96-1.34), and cis-trans 18:2 fatty acid (RR, 1.00; 95% CI, 0.86-1.16) were not significantly associated with the risk. CONCLUSIONS: Our results suggest that a higher intake of trans-fatty acids modestly increases risk of gallstone disease. This adds to the concern that partial hydrogenation of vegetable oils to form shortening and margarine can lead to adverse health effects.

Adult↗

PubMed1991

Trans fatty acids. 4. Effects on fatty acid composition of colostrum and milk.

trans Isometric fatty acids of partially hydrogenated fish oil (PHFO) consist of trans 20:1 and trans 22:1 in addition to the trans isomers of 18:1, which are abundant in hydrogenated vegetable oils, such as in partially hydrogenated soybean oil (PHSBO). The effects of dietary trans fatty acids in PHFO and PHSBO on the fatty acid composition of milk were studied at 0 (colostrum) and 21 days postpartum in sows. The dietary fats were PHFO (28% trans), or PHSBO (36% trans) and lard. Sunflower seed oil (4%) was added to each diet. The fats were fed from three weeks of age throughout the lactation period of Experiment 1. In Experiment 2 PHFO or "fully" hydrogenated fish oil (HFO) (19% trans), in comparison with coconut oil (CF) (0% trans), was fed with two levels of dietary linoleic acid, 1 and 2.7%, from conception throughout the lactation period. Feeding trans-containing fats led to secretion of trans fatty acids in the milk lipids. Levels of trans 18:1 and trans 20:1 in milk lipids, as percentages of total cis + trans 18:1 and cis + trans 20:1, respectively, were about 60% of that of the dietary fats, with no significant differences between PHFO and PHSBO. The levels were similar for colostrum and milk. Feeding HFO gave relatively less trans 18:1 and trans 20:1 fatty acids in milk lipids than did PHFO and PHSBO. Only low levels of cis + trans 22:1 were found in milk lipids.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Effect of dietary trans fatty acids on high-density and low-density lipoprotein cholesterol levels in healthy subjects.

BACKGROUND: Fatty acids that contain a trans double bond are consumed in large amounts as hydrogenated oils, but their effects on serum lipoprotein levels are unknown. METHODS: We placed 34 women (mean age, 26 years) and 25 men (mean age, 25 years) on three mixed natural diets of identical nutrient composition, except that 10 percent of the daily energy intake was provided as oleic acid (which contains one cis double bond), trans isomers of oleic acid, or saturated fatty acids. The three diets were consumed for three weeks each, in random order. RESULTS: On the oleic acid diet, the mean (+/- SD) serum values for the entire group for total, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol were 4.46 +/- 0.66. 2.67 +/- 0.54, and 1.42 +/- 0.32 mmol per liter (172 +/- 26, 103 +/- 21, and 55 +/- 12 mg per deciliter), respectively. On the trans-fatty-acid diet, the subjects' mean HDL cholesterol level was 0.17 mmol per liter (7 mg per deciliter) lower than the mean value on the diet high in oleic acid (P less than 0.0001; 95 percent confidence interval, 0.13 to 0.20 mmol per liter). The HDL cholesterol level on the saturated-fat diet was the same as on the oleic acid diet. The LDL cholesterol level was 0.37 mmol per liter (14 mg per deciliter) higher on the trans-fatty-acid diet than on the oleic acid diet (P less than 0.0001; 95 percent confidence interval, 0.28 to 0.45 mmol per liter) and 0.47 mmol per liter (18 mg per deciliter) higher on the saturated-fat diet (P less than 0.001; 95 percent confidence interval, 0.39 to 0.55 mmol per liter) than on the oleic acid diet. The effects on lipoprotein levels did not differ between women and men. CONCLUSIONS: The effect of trans fatty acids on the serum lipoprotein profile is at least as unfavorable as that of the cholesterol-raising saturated fatty acids, because they not only raise LDL cholesterol levels but also lower HDL cholesterol levels.

Cholesterol, HDL↗

PubMed2005

Dietary trans fatty acids alter diaphragm phospholipid fatty acid composition, triacylglycerol content and glucose transport in rats.

The present study evaluates the effect of dietary trans fatty acids on diaphragm phospholipid fatty acid composition, intramyocellular triacylglycerol content and insulin-stimulated glucose uptake in comparison with dietary saturated fatty acids. Male weanling WNIN rats were divided into three groups and fed for 3 months on one of the following diets containing 10 % oil differing in fatty acid composition: control diet, saturated fatty acid diet and trans fatty acid diet. Dietary trans fatty acids increased the intramyocellular triacylglycerols and decreased the ratio of 20 : 4n-6 to 18 : 2n-6 and long-chain PUFA levels (20 %) in diaphragm phospholipids, indicating inhibition of PUFA biosynthesis. However, saturated fatty acids decreased both 18 : 2n-6 and 20 : 4n-6 without change in the ratio. Trans fatty acid-induced alterations in diaphragm phospholipid fatty acid composition and intramyocellular triacylglycerol content were associated with decreased insulin-stimulated glucose transport in the diaphragm. These observations suggest that dietary trans fatty acids decrease diaphragm insulin sensitivity, possibly due to increased intramyocellular triacylglycerol accumulation and decreased long-chain PUFA in phospholipids.

Animals↗

PubMed1995

The influence of trans fatty acids on health: a report from the Danish Nutrition Council.

Trans fatty acids constitute 0-30% of the fat in Danish margarines, most in industry and bakery margarines and usually less in table margarine. The trans fatty acids make margarines more solid at room temperature and therefore provide an economical storage advantage. In British and U.S. reports from 1984-1989, the trans fatty acids were more or less acquitted of unhealthy effects. During the last 5-6 years, however, a series of new studies has been published regarding both the connection between the consumption of trans fatty acids and the occurrence of coronary heart disease and the impact on the lipoprotein level in plasma. Studies suggest that the consumption of trans fatty acids from margarine is equally, or perhaps more, responsible for the development of arteriosclerosis than saturated fatty acids. In addition, it is now clear that both the fetus and the breast-fed baby are exposed to trans fatty acids in relation to the mother's consumption. A couple of recent studies suggest a possible restrictive influence of the trans fatty acids on the weight of the fetus. The average consumption of trans fatty acids from margarine in Denmark in 1991 was approximately 2.5 g/day per person. For about 150,000 adult Danes, the consumption is assumed to be more than 5 g/day per person. On this basis, the Danish Nutrition Council recommend that the consumption of trans fatty acids is reduced as much as possible. This can be done by reducing the fat content in food and by reducing the trans fatty acid content in all Danish margarine products to 5% or less. Thereafter, the group of adult Danes, including pregnant and breast-feeding women, with a large consumption of margarine and margarine-containing products, will on average only consume 2 g of vegetable trans fatty acids/day. This corresponds to the consumption in the low-risk groups in the above-mentioned epidemiological studies. In addition, the Danish Nutrition Council encourage the producers of margarines to make products that can be marketed as 'free of trans fatty acids'.

Adult↗

PubMed1989

Lack of effects of trans fatty acids on eicosanoid biosynthesis with adequate intakes of linoleic acid.

The minimum requirement of linoleic acid to prevent effects of dietary C18 trans fatty acids on eicosanoid biosynthesis in rats was assessed. In a first experiment, six groups of animals were fed diets with a high content of trans fatty acids [20% of energy (en%)], and increasing amounts of linoleic acid (0.4 to 7.1 en%). In a second experiment, four groups of rats were fed diets designed to compare trans fatty acids with saturated and cis-monounsaturated fatty acids of the same chain length at the 2 en% linoleic acid level. After 9-14 weeks the biosynthesis of prostacyclin by pieces of aorta and the biosynthesis of hydroxy-heptadecatrienoic acid and 12-hydroxy-eicosatetraenoic acid by platelets were measured. The fatty acid compositions of aorta phospholipid and platelet lipid were also determined. Both the prostacyclin-production by aorta pieces and the production of hydroxy-heptadecatrienoic acid and 12-hydroxy-eicosatetraenoic acid by platelets appeared to be a linear function of the arachidonic acid level in aorta phospholipid and platelet lipid, irrespective of the trans fatty acid content in the diet. This indicates that trans fatty acids do not directly influence enzymes involved in eicosanoid biosynthesis. In a direct comparison with cis-monounsaturated or saturated fatty acids with 2 en% linoleic acid in the diet, only a moderate reduction in arachidonic acid level in aorta phospholipids in the group fed trans fatty acids was observed. The geometry of the double bond did not influence the arachidonic acid level in platelet lipid, although the diet rich in saturated fatty acids increased arachidonic acid levels significantly compared with all other diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1996

Variation of plasma cholesterol levels in rats fed trans fatty acids or cis fatty acids.

To investigate the effect of dietary trans fatty acids on plasma and liver lipids, 16 Sprague Dawley male rats fed the hydrogenated soybean oil (Trans fat) or Cis fat from olive oil with two similar dietary fatty acid ratios for 9 weeks were studied. Higher plasma total cholesterol and LDL (low density lipoprotein) cholesterol levels were observed in rats fed trans fat diet when compared with rats fed the cis fat diet after 2 weeks of feeding. However, no significant changes in plasma total cholesterol and LDL cholesterol levels were found in rats of both dietary groups at 4-weeks of feeding. Rats fed trans fatty acids had lower plasma total cholesterol, LDL and VLDL (very low density lipoprotein) cholesterol levels at the end of the experimental period. Although significantly (p < 0.05) lower liver triacylglycerol contents were found in rats fed trans fat diet, no significant (p > 0.05) changes in liver cholesterol and phospholipids contents were observed in rats after trans fatty acids treatment. It is interesting that lower saturated to polyunsaturated ratios in fatty acid composition of plasma VLDL total lipids were found in rats fed trans fat diet. Results from this study suggest that the changes in plasma lipoprotein cholesterol in rats fed trans fatty acids might be related to the long or the short term study, and dietary trans fatty acids may alter the plasma lipoprotein metabolism in rats.

Animals↗

PubMed2006

Trans fatty acids and insulin resistance.

Since trans fatty acids (TFA) might interfere with cell membrane functions, there are reasons to believe that high TFA intakes could affect insulin sensitivity and consequently diabetes risk. It is possible that low amounts of TFA consumed during long time-periods might be clinically relevant. Data from controlled intervention studies investigating the effects of TFA on insulin sensitivity are reviewed. The results show no significant effect of TFA on insulin sensitivity in lean healthy subjects. However, there is some evidence that TFA could impair insulin sensitivity compared to unsaturated fat in insulin resistant or diabetic individuals. This is especially true for conjugated TFA, i.e. conjugated linoleic acid (CLA), which clearly impairs insulin sensitivity. In fact, the effect of CLA on insulin action is the most dramatic adverse effect described for a dietary fatty acid. The inconsistent effect of TFA as a group might partly be due to methodological limitations (e.g. few studies, short duration or small sample size) and differences between studies in design, type and amount of TFA used. Large controlled trials have been required to demonstrate adverse effects of saturated fat on insulin sensitivity, and similar efforts will probably be needed to clarify the effect of TFA on insulin sensitivity.

Clinical Trials as Topic↗

PubMed1996

Does dietary trans fatty acid intake relate to the prevalence of coronary heart disease in Scotland?

Reports of the effects of trans fatty acids on coronary heart disease are inconsistent. Trans fatty acids may particularly influence coronary risk when linoleic acid levels are low, a situation which occurs in Scotland where prevalence of coronary heart disease is also very high. The link between trans fatty acid intake and prevalent coronary heart disease was therefore investigated in the Scottish Heart Health Study population. Trans fatty acid intakes were calculated from 10/359 sets of food-frequency questionnaire data obtained from the cross-sectional survey of men and women aged 40-59 years. Logistic regression analysis was used to calculate the odds ratios for prevalent coronary heart disease by fifths of dietary intake of total, natural and commercial hydrogenation-derived trans fatty acid. The group who had undiagnosed coronary heart disease at the time of survey was the pertinent group for examining the possible causative effects of trans fatty acid intake. After adjustment for the confounding factors (i.e. age, weight, height, smoking, level of physical activity, blood pressure, total energy intake and intakes of saturated fat, linoleic acid and the antioxidant vitamins) the odds of undiagnosed coronary heart disease for men, relative to the lowest intake fifth, did not differ significantly from unity by total or commercially-derived trans fatty acid intake. Odds were around 35% smaller in the higher intake fifths of naturally-derived trans fatty acids. For women, the odds of undiagnosed coronary heart disease tended to be greater in the higher fifths of total (odds ratio 1.36 (95% confidence interval 0.94, 1.89)) and hydrogenated (1.26 (0.92, 1.72)) trans fatty acid relative to the lowest fifth, but only reached significance in the third fifth of total trans fatty acid (1.36 (1.01, 1.83)). Dietary total and commercially-derived trans fatty acids failed to influence the odds of coronary heart disease for men, even though a significant increase in the ratio of low density plus very low density lipoprotein to high density lipoprotein-cholesterol occurred with trans fatty acid intake. The results, therefore, do not support a major effect of dietary trans fatty acid from commercial hydrogenation on coronary heart disease risk in these Scottish men. The results for women are less clear, and the possibility remains that individuals at the high extreme of trans fatty acid intake, who may be essential fatty acid deficient, are at enhanced risk of coronary heart disease.

Adult↗

PubMedDate not supplied

Dietary effects of trans fatty acids.

The dietary effects of the trans fatty acids in hydrogenated fats in health and disease deserves consideration for at least two reasons. One, trans fatty acids are becoming increasingly important as a source of calories in all industrialized countries, and two, their structural differences from the fatty acids in unhydrogenated fats offer a means of exploring uncharted areas in lipid metabolism. Such an exploration would have been impossible twenty years ago; some areas are still inaccessible because of a lack of methodology.

Animals↗

PubMed1996

Dietary trans-fatty acids and serum lipoproteins in humans.

Trans-fatty acids increase serum LDL-cholesterol and decrease HDL-cholesterol levels in humans when substituted for cis unsaturated fatty acids in the diet. Trans-fatty acids also increase lipoprotein (a) levels relative to other fatty acids. The effects on LDL and HDL may be mediated by the cholesteryl ester transfer protein.

Carrier Proteins↗

PubMed2002

Effects of feeding pigs increasing levels of C 18:1 trans fatty acids on fatty acid composition of backfat and intramuscular fat as well as backfat firmness.

Forty Large White pigs were fed from 30 kg to 103 kg body mass on diets supplemented with 6% of pure high-oleic sunflower oil (HO) or HO plus increasing amounts of partially hydrogenated rape seed oil (HR; 1.85%, 3.70%, 5.55%), containing high levels of delta 6 to delta 11 C 18:1 trans fatty acid isomers. Increasing dietary C 18: trans fatty acids resulted in a linear increase in C 18:1 trans fatty acids and conjugated linoleic acid (cis-9, trans-11 CLA) in backfat (BF) as well as in neutral lipids (NL) and phospholipids (PL) of M. long. dorsi. Thus, the rate of bioconversion of trans vaccenic acid (TVA) into CLA and incorporation of C 18:1 trans and CLA into pig adipose tissue was not limited up to 25 g total C 18:1 trans fatty acids including 3.3 g of TVA per kg feed. BF was higher in C 18:1 trans fatty acids and CLA than M. long. dorsi NL and PL. In BF and NL the sum of saturated fatty acids (SFA) increased with increasing dietary amounts of HR, while in PL SFA were reduced. Thus, according to their physical properties, C 18:1 trans fatty acids partly replaced SFA in PL. Firmness of backfat was also significantly increased (P < 0.05) with increasing amounts of HR in feed.

Adipose Tissue↗

PubMed1995

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

The objective of this study was to evaluate the composition of trans fatty acids in the subcutaneous fat of Canadians relative to the composition of dietary sources of trans fatty acids. The fatty acid composition, total trans acid content, and the geometric and positional isomer distribution of unsaturated fatty acids of subcutaneous adipose tissue of Canadians were determined using a combination of capillary gas-liquid chromatography and silver nitrate thin-layer chromatography. The mean total trans fatty acid content was 6.80% at the abdominal site and 5.80% at the lateral thigh site. Total trans isomers of linoleic acid (18:2n-6) were present at 1.17% in abdominal and 1.59% in thigh adipose tissue, with 9c.12t-18:2 being the most prevalent isomer followed by 9c-13t-18:2 and 9t,12c,-18:2. The oleic acid (18:1) trans isomer distribution in adipose tissue differed from that in butter fat, but it was similar to that in partially hydrogenated vegetable oils. The reverse was true for the 18:1 cis isomers. Total 18:1 trans isomers were inversely related to 18:2n-6 content in adipose tissue, suggesting the trans fatty acid intake is inversely related to the intake of linoleic acid. Partially hydrogenated vegetable oils appear to be the major source of trans fatty acids in adipose tissue of Canadians.

Adipose Tissue↗

PubMed2003

Postprandial effects of dietary trans fatty acids on apolipoprotein(a) and cholesteryl ester transfer.

BACKGROUND: The consumption of trans fatty acids adversely affects fasting plasma lipoprotein concentrations. OBJECTIVE: This study aimed to investigate whether postprandial lipoprotein metabolism is affected by the consumption of trans fatty acids. DESIGN: In a randomized crossover study, 19 healthy men consumed fatty meals that were identical except that 10% of energy was provided as trans 18:1 acids in the trans meal and as oleic acid in the cis meal. RESULTS: The meals induced similar responses in plasma lipids. Cholesteryl ester transfer (CET) was activated after consumption of both meals (P < 0.0001); however, it was 28% higher after the trans meal than after the cis meal (280 +/- 129 compared with 219 +/- 116 nmol cholesteryl ester/mL plasma * 6 h; time x diet interaction: P < 0.0001). Plasma apolipoprotein(a) [apo(a)] concentrations remained constant; however, triacylglycerol-rich lipoproteins formed 4 h after ingestion of the trans meal contained a higher concentration of apo(a) than did those formed after ingestion of the cis meal (48.9 +/- 6.6 compared with 39.6 +/- 5.4 U/L; P < 0.02). The change in CET and in the proportion of plasma apo(a) in the triacylglycerol-rich lipoprotein fractions correlated with indexes of alimentary lipemia. CONCLUSIONS: Consumption of meals high in trans fatty acids results in higher CET and postprandial lipoprotein concentrations enriched in apo(a) than does consumption of meals free of trans fatty acids. This study highlights the importance of double-bond configuration in determining postprandial lipoprotein composition.

Adult↗

PubMed1995

Trans fatty acids and their effects on lipoproteins in humans.

Trans fatty acids raise plasma low-density lipoprotein (LDL) cholesterol levels in volunteers when exchanged for cis unsaturated fatty acids in the diet. In addition, trans fatty acids may lower high-density lipoprotein (HDL) cholesterol levels and raise triglyceride and lipoprotein(a) levels in plasma. Trans and cis unsaturated fatty acids are thus not equivalent, and diets aimed at reducing the risk of coronary heart disease should be low in both trans and saturated fatty acids.

Cholesterol, HDL↗

PubMed2005

[Margarine's trans-fatty acid composition: modifications during the last decades and new trends].

Trans fatty acids isomers are formed during the hydrogenation process used in the food industry to harden oils. In the last decades there has been a great controversy about the consumption of margarine due to the levels of trans fatty acids they contain. While in the eighties consumption of margarines was considered healthy, during the nineties several studies indicated that consumption of 18:1t increased LDL-cholesterol levels and decreased HDL-cholesterol level, and was related with an increased risk of coronary heart disease. The publicity about the unfavourable effects of trans fatty acid consumption seems to have influenced margarine producers to reduce the trans fatty acid content of margarines. Meanwhile USA has adopted a new legislation about trans fatty acid labelling. In Europe, Dinamarca has limited the maximum level of trans fatty acids allowed in food products.

Diet, Fat-Restricted↗

PubMed2000

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.

Adipose Tissue↗