Isomeric trans fatty acids in the U.S. diet

Since actual consumption data for trans fatty acid (FA) intakes for the U.S. population do not exist, estimates of trans fatty acids (FAs) available in the U.S. food supply have been calculated from U.S. Department of Agriculture-Economic Research Service (USDA-ERS) fats and oils production figures and food disappearance data for fats and oils. Based on weighted averages for the trans levels in each fats and oils category, these estimates of trans FAs available in the U.S. food supply range from 12.5 to 15.2 g/person/day (average 13.3 +/- 1.1 g/person/day). Estimates of trans FA consumption have been calculated; these estimates predict a wide range from 1.6 to 38.7 g/person/day. These calculations are based on published estimates of trans FAs available in the total fat of 5-15%, and the total fat intake (range 31-258 g/person/day) of a representative sample of adults (ages 20-59) as determined by the Lipid Research Clinics (LRC). Using an equation based on a relationship between trans FAs in adipose tissue and dietary fat, an intake range of 0.7-28.7 g/person/day trans FAs for the same LRC fat consumption data can be predicted. Adipose tissue isomer profiles that indicate 90-95% of the trans FAs in the tissues comes from partially hydrogenated vegetable fats and oils allow us to predict a dietary intake range from 11.1 to 27.6 g/person/day trans FAs. The significance of these estimates to nutrition policy is discussed.     

Isomeric trans fatty acids in the U.S. diet.

Since actual consumption data for trans fatty acid (FA) intakes for the U.S. population do not exist, estimates of trans fatty acids (FAs) available in the U.S. food supply have been calculated from U.S. Department of Agriculture-Economic Research Service (USDA-ERS) fats and oils production figures and food disappearance data for fats and oils. Based on weighted averages for the trans levels in each fats and oils category, these estimates of trans FAs available in the U.S. food supply range from 12.5 to 15.2 g/person/day (average 13.3 +/- 1.1 g/person/day). Estimates of trans FA consumption have been calculated; these estimates predict a wide range from 1.6 to 38.7 g/person/day. These calculations are based on published estimates of trans FAs available in the total fat of 5-15%, and the total fat intake (range 31-258 g/person/day) of a representative sample of adults (ages 20-59) as determined by the Lipid Research Clinics (LRC). Using an equation based on a relationship between trans FAs in adipose tissue and dietary fat, an intake range of 0.7-28.7 g/person/day trans FAs for the same LRC fat consumption data can be predicted. Adipose tissue isomer profiles that indicate 90-95% of the trans FAs in the tissues comes from partially hydrogenated vegetable fats and oils allow us to predict a dietary intake range from 11.1 to 27.6 g/person/day trans FAs. The significance of these estimates to nutrition policy is discussed.     

Intensification of essential fatty acid deficiency in the rat by dietary trans fatty acids

Two studies were conducted using male rats to assess the effect of trans fatty acids upon essential fatty acid (EFA) deficiency. In the first study 5% corn oil (CO), hydrogenated coconut oil (HCNO) or margarine stock (MS, partially hydrogenated soybean oil) were fed, and the levels of trans fatty acids in tissue lipids were measured. The trans fatty acids present in MS were found to intensify EFA deficiency and to be retained in tissue lipids to a high degree, especially in heart phospholipids (PL). In the second study, as the level of trans fatty acids increased in the diet, increasingly higher levels of trans fatty acids were deposited in the heart PL. As dietary trans acid increased, a decrease in total omega 6 fatty acids, and a decrease in the sum of 18:2 omega 6 + 20:4 omega 6 - 20:3 omega 9 fatty acids in heart PL occurred, both criteria indicating a shift toward an increasing EFA deficiency state. Studies of delta 5 desaturase activity of liver microsomes in selected groups showed an increase in the conversion of 20:3 omega 6 to 20:4 omega 6 as the trans fatty acid level in the diet increased.     

Variability in the trans fatty acid content of foods within a food category: implications for estimation of dietary trans fatty acid intakes.

OBJECTIVE: Currently, the published information on trans fatty acid composition of foods is incomplete and of questionable accuracy. Detailed fatty acid analysis of over 200 foods was undertaken for the purpose of determining the variability in trans fatty acid content among foods within a product category, and the significance of this variability to the estimation of trans fatty acids intakes from analysis of dietary intake data. METHODS: The analysis of food fatty acids used gas-liquid chromatography with 100 m capillary columns and standardized methodologies for food sampling, fat extraction, separation and quantification of trans fatty acid isomers. For the purposes of this report, trans refers to all non-naturally occurring isomers including trans, cis-trans, geometric and positional isomers. RESULTS: The results show that the amount of trans fatty acids varies considerably among foods within a category, reflecting differences in the fats and oils used in the manufacturing or preparation process. For example, the range of trans fatty acids in 17 brands of crackers was 23 to 51% total fatty acids, representing differences of from 1 to 13 g trans fatty acids per 100 g cracker. The large errors that may arise in estimates of the trans fatty acid intake of an individual are illustrated by analyses of the potential trans fatty acid intake in a sample diet, for each food as calculated using the minimum and maximum values for trans fatty acids within a given category. The results of these analyses show estimates of trans fatty acid intake from a low of 1.4 to 25.4 g a day for the same diet. CONCLUSION: This study shows that the wide variability in trans fatty acid content of different foods may result in large errors in the estimation of trans fatty acid intake of individuals and, potentially, groups.     

Isomeric fatty acids in the US diet: levels and health perspectives

Data on market size, market share, and compositional changes of various products made from partially hydrogenated fats and oils were used to estimate current, previous, and predicted levels of trans fatty acids in the US diet. Recent literature and various perceptions of the toxicological, physiological, and nutritional effects of trans fatty acids were reviewed. Trans acid availability has changed little during the last 15-20 yr and currently is estimated to be approximately 7.6 g X person-1 X day-1. Modest decreases in total fat intake, including trans fatty acid intake, may occur in the future if consumers adopt certain dietary recommendations. We believe that concerns about possible relationships of trans fatty acids to development of atherosclerotic disease or cancer are not supported by reliable data. Numerous literature accounts support the conclusion that trans fatty acids do not pose any harm to humans or animals consuming a balanced diet containing adequate linoleic acid.     

Fatty acid composition of Costa Rican foods including trans fatty acid content

To further understand the fatty acid–disease relationships in an epidemiologic context, detailed composition tables are required. The composition of the major saturated, monounsaturated, and polyunsaturated fatty acids that are most abundant in the diet, is available for numerous foods in many countries, but data on the content of individual fatty acids with relative low abundance are scarce. We conducted a study to establish a fatty acid composition database that includes fatty acids with low relative abundance as well as trans fatty acids for the main sources of fat in the Costa Rican diet. Fatty acids were determined by gas chromatography. We present in-depth fatty acid composition tables for foods that are commonly used in Costa Rica. These analyses include information on alpha-linolenic, gamma-linolenic, arachidonic acid and trans fatty acids, which are important for health but where information is scarce. Of particular interest is the high content of trans fatty acids in partially hydrogenated soybean oil in Costa Rica, although decreasing over time. In a period of 10 years the amount of total trans fatty acids in Costa Rican soybean oil has decreased from an average of 20 to 1.5%, while alpha-linolenic has increased from an average of 1.87 to 6.06%. Our data will be of special interest for studies on Latin American countries requiring dietary information.     

The linoleic acid and trans fatty acids of margarines.

Fifty brands of margarine were analysed for cis-polyunsaturated acids by lipoxidase, for trans fatty acid by infared spectroscopy, and for fatty acid composition by gas-liquid chromatography. High concentrations of trans fatty acids tended to be associated with low concentrations of linoleic acid. Later analyses on eight of the brands, respresenting various proportions of linoleic to trans fatty acids, indicated that two of them contained still higher levels of trans fatty acids (greater than 60%) and negligible amounts of linoleic acid. It is proposed that margarine could be a vehicle for the distribution of some dietary linoleic acid and that the level of linoleic acid and the summation of the saturated plus trans fatty acids be known to ascertain nutritional characteristics.     

Isomeric fatty acids in the US diet: levels and health perspectives.

Objective: Alcohol drinkers are generally considered to underreport their alcohol intake, but little is known about whether they correctly report their energy intake (EI). We assessed the validity of the reported energy intake of alcohol drinkers using the 24-hour urinary (U) excretion of potassium (K) and sodium (Na) as biomarkers.

Methods: A total of 2,124 men and 1,998 women 25 to 74 years of age with a 24-hour urine collection, a random sample of the Belgian Interuniversity Research on Nutrition and Health (BIRNH), were studied. Dietary intake (D), including alcohol consumption, was assessed by a one-day food record. Basal metabolic rate (BMR) was predicted from age, gender and weight. As a measure for the degree of reporting error, D-K/U-K, D-Na/U-Na, EI/U-K, Non-alcohol EI/U-Na (NAEI/U-Na), EI/U-Na, EI/U-creatinine and EI/BMR ratios were calculated and compared among non-, moderate and heavy drinkers in both genders.

Results: EI, NAEI and all seven ratios examined generally increased with the level of alcohol intake in both genders. After adjustment for age, body mass index, smoking and educational level, most ratios were significantly higher in moderate drinkers (p < 0.02 to p < 0.0001) and in heavy drinkers (all p < 0.0001) than in non-drinkers. These differences were most significant in male heavy drinkers. The exceptions were D-K/U-K, D-Na/U-Na and NAEI/U-Na in moderate and female heavy drinkers and EI/U-K in male moderate drinkers. The estimated amount of the overreporting of EI by heavy drinkers was 27.8% in men and 13.7% in women.

Conclusions: This study provides evidence that EI and NAEI obtained from the BIRNH study was overreported among alcohol drinkers, especially among male heavy drinkers. It also indicates that EI from alcohol replaced EI from food.     

N-3 fatty acids reduced trans fatty acids retention and increased docosahexaenoic acid levels in the brain

Introduction: The levels of docosahexaenoic acid (DHA, 22:6n-3) and arachidonic acid (AA, 20:4n-6) are critical for the normal structure and function of the brain. Trans fatty acids (TFA) and the source of the dietary fatty acids (FA) interfere with long-chain polyunsaturated fatty acids (LC-PUFA) biosynthesis.

Objectives: The aim of this study was to investigate the effect of TFA supplementation in diets containing different proportions of n-9, n-6, and n-3 FA on the brain FA profile, including the retention of TFA, LC-PUFA levels, and n-6/n-3 PUFA ratios. These parameters were also investigated in the liver, considering that LC-PUFA are mainly bioconverted from their dietary precursors in this tissue and transported by serum to the brain. Also, stearoyl-CoA desaturase-1 (SCD1) and sterol regulatory element-binding protein-1c (SREBP-1c) gene expressions were evaluated.

Methods: Male CF1 mice were fed (16 weeks) diets containing different oils (olive, corn, and rapeseed) with distinct proportions of n-9, n-6, and n-3 FA (55.2/17.2/0.7, 32.0/51.3/0.9, and 61.1/18.4/8.6), respectively, substituted or not with 0.75% of TFA. FA composition of the brain, liver, and serum was assessed by gas chromatography.

Results: TFA were incorporated into, and therefore retained in the brain, liver, and serum. However, the magnitude of retention was dependent on the tissue and type of isomer. In the brain, total TFA retention was lower than 1% in all diets.

Discussion: Dietary n-3 PUFA decreased TFA retention and increased DHA accretion in the brain. The results underscore the importance of the type of dietary FA on the retention of TFA in the brain and also on the changes of the FA profile.     

Determination of trans fatty acid levels by FTIR in processed foods in Australia

Health authorities around the world advise 'limiting consumption of trans fatty acid', however in Australia the trans fatty acid (TFA) content is not required to be listed in the nutrition information panel unless a declaration or nutrient claim is made about fatty acids or cholesterol. Since there is limited knowledge about trans fatty acid levels in processed foods available in Australia, this study aimed to determine the levels of TFA in selected food items known to be sources of TFA from previously published studies. Food items (n=92) that contain vegetable oil and a total fat content greater than 5% were included. This criterion was used in conjunction with a review of similar studies where food items were found to contain high levels of trans fatty acids. Lipids were extracted using solvents. Gravimetric methods were used to determine total fat content and trans fatty acid levels were quantified by Attenuated Total Reflectance Fourier Transform Infrared spectroscopy. High levels of trans fatty acids were found in certain items in the Australian food supply, with a high degree of variability. Of the samples analysed, 13 contained greater than 1 g of trans fatty acids per serving size, the highest value was 8.1 g/serving. Apart from when the nutrition information panel states that the content is less than a designated low level, food labels sold in Australia do not indicate trans fatty acid levels. We suggested that health authorities seek ways to assist consumers to limit their intakes of trans fatty acids.     

Effects of a normolipidic diet containing trans fatty acids during perinatal period on the growth, hippocampus fatty acid profile, and memory of young rats according to sex

ObjectiveTo investigate whether dietary trans fatty acids (TFAs) are incorporated in the hippocampus and its effects on the growth and aversive and spatial memories of young rats.MethodsWistar rat offspring whose mothers were fed with normolipidic diets containing soybean oil (soy group) or hydrogenated vegetable oil (trans group) during gestation and lactation were used. Male and female pups received the same diets as their mothers until the end of behavioral testing. The composition of fatty acids in the total lipids of the diets and hippocampus was quantified by gas chromatography. The results were evaluated by Student’s t test or analysis of variance followed by the Bonferroni correction.ResultsThe trans male and female body weights were higher during lactation and after weaning, with trans males having the lower body weight of the two. There was incorporation of 0.11% and 0.17% of TFAs in the hippocampi of male and female rats, respectively. During passive avoidance test, there was no significant difference. In the water maze test, there was no significant difference between male groups in the training and retention phases, except on day 4, when there was a significant decrease in latency in trans males. Trans females were worse on day 2 only and showed an improvement in spatial memory during the probe trial.ConclusionThe TFAs were incorporated in small amounts in the hippocampus and did not affect aversive memory. However, spatial memory was modified in young rats fed with a diet rich in TFAs. These findings suggested that, in addition to the TFA content of the diet provided, it is important to consider the provision of essential fatty acids and the ω-6/ω-3 ratio.     

Comparison between plasma and erythrocyte fatty acid content as biomarkers of fatty acid intake in US women

BACKGROUND: Erythrocyte fatty acids may be superior to plasma fatty acids for reflecting long-term fatty acid intake because of less sensitivity to recent intake and a slower turnover rate. OBJECTIVE: The objective was to compare the fatty acid content of erythrocytes with that of plasma with respect to their abilities to reflect usual fatty acid intake. DESIGN: Fatty acids in plasma and erythrocytes were measured by capillary gas-liquid chromatography in 306 US women aged 43-69 y. Fatty acid intake was assessed with a food-frequency questionnaire, which was validated for measuring intakes of various fatty acids. RESULTS: Docosahexaenoic acid (DHA, 22:6n-3) in erythrocytes and plasma provided the strongest correlations with its intake, but erythrocyte DHA concentrations [Spearman's partial correlation coefficient (r(s))=0.56] were better than plasma DHA concentrations (r(s)=0.48) as a biomarker. Total trans fatty acids (r(s)=0.43) and total 18:1 trans isomers (r(s)=0.42) in erythrocytes were also more strongly correlated with intake than were those in plasma (r(s)=0.30 and r(s)=0.29, respectively). Moderate correlations were observed for linoleic acid (18:2n-6; erythrocytes, r(s)=0.24; plasma, r(s)=0.25), alpha-linolenic acid (18:3n-3; erythrocytes, r(s)=0.18; plasma, r(s)=0.23), and eicosapentaenoic acid (20:5 n-3; erythrocytes, r(s)=0.38; plasma, r(s)=0.21). For polyunsaturated and trans fatty acids, correlations between intakes and biomarkers improved moderately when average intakes over previous years were used. CONCLUSION: Erythrocyte n-3 fatty acids of marine origin and trans fatty acid content are suitable biomarkers for long-term intake.     

Omega-3 fatty acid content of the US food supply.

In this study, levels and sources of omega-3 fatty acids (FA) available for consumption in the US food supply, dating from 1935, are estimated. omega-3 FA assessed are eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and linolenic acid (LNA). Estimates are based on annual per capita food use data and data on the omega-3 FA content of foods. Although fish use increased, the EPA level was slightly lower in 1985 than in 1935-1939, reflecting a marked decline in use of certain fatty fish. The level of DHA increased, due to greater use of poultry. The level of LNA increased because of greater use of soybean oil. These estimates are currently the only source of data on omega-3 FA in the American diet.     

傅立叶变换红外光谱法分析食品及油脂中反式脂肪酸

目的：采用傅立叶变换红外光谱法定性定量分析食品及油脂中反式脂肪酸含量。方法：食品中提取的脂肪或油脂样品直接置于红外光谱仪的水平衰减全反射（HATR）部件的槽式ZnSe晶体上,氘化三甘氨酸硫酸酯（DTGS）检测器检测。通过966 cm-1处反式双键的特征峰进行定性,由峰面积与反式脂肪酸含量的线性校准曲线定量计算反式脂肪酸在油脂中的百分含量。结果：该方法可通过反式双键的特征峰对样品油脂中的反式脂肪酸进行准确定量。结论：此方法具有简单、快速、准确的特点,适用于食品营养标签的测定。     

Omega-3 fatty acid content of the US food supply.

In this study, levels and sources of omega-3 fatty acids (FA) available for consumption in the US food supply, dating from 1935, are estimated. omega-3 FA assessed are eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and linolenic acid (LNA). Estimates are based on annual per capita food use data and data on the omega-3 FA content of foods. Although fish use increased, the EPA level was slightly lower in 1985 than in 1935-1939, reflecting a marked decline in use of certain fatty fish. The level of DHA increased, due to greater use of poultry. The level of LNA increased because of greater use of soybean oil. These estimates are currently the only source of data on omega-3 FA in the American diet.