Adipose tissue fatty acids as biomarkers of dietary exposure in Danish men and women

Comparison between omega-3 and omega-6 polyunsaturated fatty acid intakes as assessed by a food frequency questionnaire and erythrocyte membrane fatty acid composition in young children

OBJECTIVE

We conducted a dietary validation study in youth aged 1-11 years by comparing dietary intake of omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) as assessed by a parent-completed semiquantitative food frequency questionnaire (FFQ) over time to erythrocyte membrane composition of the same fatty acids.

DESIGN

The study population included youth aged 1-11 years who were participants in the Diabetes Autoimmunity Study in the Young (DAISY), a longitudinal study in Denver, Colorado that is following a cohort of youth at risk for developing type I diabetes. Four hundred and four children who had erythrocyte membrane fatty acid data matched to an FFQ corresponding to the same time frame for a total of 917 visits (matches) were included. PUFA intake was expressed both as g/day (adjusted for total energy) and as percent of total fat intake. We used mixed models to test the association and calculate the correlation between the erythrocyte membrane estimates and PUFA intake using all records of data for each youth.

RESULTS

Intakes of total omega-3 fatty acids (beta=0.52, P<0.0001, rho=0.23) and marine PUFAs (beta=1.62, P<0.0001, rho=0.42), as a percent of total fat in the diet, were associated with percent of omega-3 and marine PUFAs in the erythrocyte membrane. Intakes of omega-6 PUFAs (beta=0.04, P=0.418, rho=0.05) and arachidonic acid (beta=0.31, P=0.774, rho=0.01) were not associated.

CONCLUSIONS

In these young children, an FFQ using parental report provided estimates of average long-term intakes of marine PUFAs that correlated well with their erythrocyte cell membrane fatty acid status.

Intake and adipose tissue composition of fatty acids and risk of myocardial infarction in a male Portuguese community sample

OBJECTIVE

To evaluate the relation between intake and adipose tissue composition of fatty acids and acute myocardial infarction in Portuguese men.

DESIGN

Case-control study. Diet was assessed using a semiquantitative food frequency questionnaire. In 49 case and 49 control subjects, adipose tissue composition was assessed by gas-liquid chromatography.

SUBJECTS/SETTING

Population-based; subjects were 297 consecutively admitted cases of first acute myocardial infarction in a tertiary care hospital who were aged>or=40 years. Three hundred ten community controls were selected by random-digit dialing.

MAIN OUTCOME MEASURE

Odds ratio (OR).

STATISTICAL ANALYSIS PERFORMED

Logistic regression, adjusting for age, education, family history of acute myocardial infarction, smoking, physical activity, body mass index, and energy intake.

RESULTS

Total fat intake (OR 0.45, fourth quartile, P=0.02), lauric acid (OR 0.44, fourth quartile, P=0.02), palmitic acid (OR 0.58, fourth quartile, P=0.03), and oleic acid (OR 0.42, fourth quartile, P=0.03) were inversely associated with acute myocardial infarction. No significant effects were found for the remaining fatty acids. In the adipose tissue composition data, the adjusted risk estimates of acute myocardial infarction for the highest vs the lowest tertile were 0.16, 0.14, and 0.04 for lauric, oleic, and trans-fatty acids, respectively. A significant direct association was found for palmitic and linoleic acids (adjusted ORs for the highest tertile were 9.02 and 3.63, respectively).

CONCLUSIONS

Low intake of total fat and lauric acid from dairy products was associated with acute myocardial infarction. The association of polyunsaturated fatty acids with risk of acute myocardial infarction was nonsignificant after adjustment for energy intake and confounders. Recommendations on fatty acid intake should aim for both an upper and lower limit.

Cortisol secretary pattern and glucocorticoid feedback sensitivity in women from a Mediterranean area: relationship with anthropometric characteristics, dietary intake and plasma fatty acid profile

BACKGROUND

Chronic stress is associated with a dysfunctional hypothalamic-pituitary-adrenal (HPA) axis consisting on disturbances on the cortisol response and lipid metabolism.

OBJECTIVE

To evaluate the HPA axis activity in women from a Mediterranean area, comparing three different measurements: daily cortisol secretory variability, postprandial cortisol secretion and glucocorticoid feedback sensitivity. In addition, HPA axis disturbance is correlated with dietary habits and plasma fatty acid profiles.

DESIGN

The participants were 41 women born during the first 6 months of 1960 and living in a Mediterranean area (Murcia, Spain). They were of normal weight, with a waist circumference of 80.5 +/- 9.3 cm. Their salivary cortisol levels, 7-day dietary record and plasma fatty acid profile were evaluated. Daily cortisol variability and postlunch cortisol secretion were recorded and a dexamethasone suppression test is performed in order to detect possible HPA disturbance.

RESULTS

Both the methods used for HPA axis evaluation were positively correlated (r = 0.448, P = 0.004). Subjects with normal diurnal curves (high cortisol variability) showed significantly higher cortisol values in the morning and postprandial cortisol secretion than women with pathological curves (medium and low variability). Cortisol variability was inversely correlated with waist circumference (r = -0.312, P = 0.047), suggesting that a disturbed HPA axis response may lead to an android pattern of body fat distribution. Dietary fat and saturated fatty acid intake were lower in the high cortisol variability group, while monounsaturated fatty acid intake was higher (P < 0.05). No major differences were reported in plasma fatty acid profile.

CONCLUSIONS

A disturbed HPA axis is associated with abdominal fat distribution and a higher content of fat and saturated fatty acids in the diet. Women who chose a dietary pattern closer to the Mediterranean diet, with high monounsaturated fatty acid intake, showed lower levels on HPA axis disturbance.

Dietary fish intake and plasma phospholipid n-3 polyunsaturated fatty acid concentrations in men and women in the European Prospective Investigation into Cancer-Norfolk United Kingdom cohort

BACKGROUND

The n-3 polyunsaturated fatty acids (n-3 PUFAs) docosahexaenoic acid and eicosapentaenoic acid, found in fish and fish-oil supplements and also formed by conversion of alpha-linolenic acid in soy and rapeseed (canola) oils, are thought to have cardioprotective effects.

OBJECTIVE

Because the relative feasibility and measurement error of dietary methods varies, this study compared fish and fish-oil intakes obtained from 4 dietary methods with plasma n-3 PUFAs in men and women in a general population.

DESIGN

The study participants were 4949 men and women aged 40-79 y from the European Prospective Investigation into Cancer-Norfolk United Kingdom cohort. Measurements of plasma phospholipid n-3 PUFA concentrations and fish intakes were made with the use of 4 dietary methods (food-frequency questionnaire, health and lifestyle questionnaire, 7-d diary, and first-day recall from the 7-d diary).

RESULTS

Amounts of fish consumed and relations with plasma phospholipid n-3 PUFAs were not substantially different between the 4 dietary methods. Plasma n-3 PUFA concentrations were significantly higher in women than in men, were 20% higher in fish-oil consumers than in non-fish-oil consumers, and were twice as high in fatty fish consumers as in total fish consumers. Only approximately 25% of the variation in plasma n-3 PUFA was explained by fish and fish-oil consumption.

CONCLUSIONS

This large study found no substantial differences between dietary methods and observed clear sex differences in plasma n-3 PUFAs. Because variation in n-3 PUFA was only partially determined by fish and fish-oil consumption, this could explain the inconsistent results of observational and intervention studies on coronary artery disease protection.

Ácidos graxos como marcadores biológicos da ingestão de gorduras

Os ácidos graxos da dieta têm sido associados ao desenvolvimento de doenças crônicas. Os inquéritos alimentares, utilizados em estudos clínicos e epidemiológicos para estimativa da ingestão de nutrientes, apresentam limitações na coleta de informações. Nesse sentido, a utilização da composição de ácidos graxos do plasma e do tecido adiposo como marcadores do tipo de gordura alimentar pode fornecer uma medida mais acurada da ingestão de gorduras. Esta pesquisa tem como objetivo evidenciar aspectos metabólicos de alguns ácidos graxos e o papel como marcadores da ingestão de gorduras, e apresentar as técnicas analíticas empregadas na sua determinação. A biópsia do tecido adiposo, com determinação da composição de ácidos graxos, fornece uma informação a longo prazo da ingestão de gorduras, enquanto que a avaliação da composição das frações lipídicas séricas representa a ingestão a curto e médio prazos. Os ácidos graxos essenciais, os ácidos graxos saturados com número ímpar de carbonos (15:0 e 17:0) e os ácidos graxos trans, por não apresentarem síntese endógena, são utilizados como marcadores biológicos da ingestão de gorduras ou de sua própria ingestão. As principais técnicas utilizadas para a determinação de ácidos graxos são a cromatografia gasosa e a cromatografia líquida de alta precisão. No presente momento, o uso de marcadores biológicos para a ingestão de gorduras, associados aos inquéritos alimentares, representa a forma mais completa de avaliação da ingestão de gorduras.

Assessment of erythrocyte phospholipid fatty acid composition as a biomarker for dietary MUFA, PUFA or saturated fatty acid intake in a controlled cross-over intervention trial

Background

Dietary intervention trials rely on self-reported measures of intake for assessment of energy and macronutrient composition. Dietary fat intake is of particular interest due to strong associations with pathophysiology. In epidemiological trials phospholipid fatty acid composition may reflect composition of habitual diet, although strong correlations have been identified only for essential polyunsaturated fatty acids (PUFAs). Preliminary evidence shows that saturated fatty acids (SFA) C15:0 and C17:0 may be acceptable biomarkers. This study measured changes in erythrocyte membrane fatty acids during a period of strictly controlled fat feeding to investigate their use as a short-term marker of compliance, particularly for intake of SFAs.

Results

This was a randomised cross-over trial in which diet was provided and strictly controlled. 20 healthy, male subjects were given a 40 energy % (en%) fat diet, high in saturated (high-SFA, 20 en%) or unsaturated (high-USFA, 24 en%) fatty acids for 2 periods of 3 weeks. Subjects were residential during intervention with all food and beverages provided. Dietary composition was verified by direct chemical analysis. Blood samples were collected on days 1,7,14, 21 and analysed for red blood cell (RBC) membrane fatty acid composition. Pearson correlation showed RBC fatty acid composition to mimic dietary composition by 3 weeks, but the relationships were weak. Of the SFAs only RBC C16:0 decreased in response to decreased dietary content on high-USFA treatment (ANOVA, diet, P < 0.05). Of the USFAs, higher levels of C18:1 MUFA, C20:4 and C22:6 long chain PUFA on high-USFA diet lead to higher C18:1, C20:4 and C22:6 within RBCs (ANOVA, time*diet, P < 0.05). Pearson's correlation was significant between dietary and RBC fatty acids during the 21d dietary manipulation for C18:1, and C20:5, C22:6 only (P < 0.05).

Conclusion

RBC membrane fatty acids cannot reliably be used as an independent measure of compliance for dietary SFA intake in short-term studies. The MUFA oleic acid and PUFAs EPA and DHA may be more useful as markers of compliance during short term intervention trials.

Fasting whole blood as a biomarker of essential fatty acid intake in epidemiologic studies: comparison with adipose tissue and plasma

Biomarkers could provide a more accurate measure of long-term intake than questionnaires. Adipose tissue is considered the best indicator of long-term essential fatty acid intake, but other tissues may prove equally valid. The authors evaluated the ability of fasting whole blood, relative to fasting plasma and adipose tissue, to reflect fatty acid intake. Costa Rican men (n = 99) and women (n = 101) completed a 135-item food frequency questionnaire and provided adipose tissue and blood samples from 1999 to 2001. Fatty acids were identified by using capillary gas chromatography. Correlation coefficients adjusted for age, sex, and body mass index were calculated. Diet-tissue correlation coefficients for alpha-linolenic acid and linoleic acid, respectively, were 0.38 and 0.43 in whole blood, 0.51 and 0.52 in adipose tissue, and 0.39 and 0.41 in plasma. High correlations were observed between whole-blood alpha-linolenic and linoleic acid and adipose tissue (r = 0.59 and r = 0.67) and plasma (r = 0.96 and r = 0.88), respectively. Results show that fasting whole blood is a suitable biomarker of long-term essential fatty acid intake, and its performance is comparable to that of fasting plasma. Thus, fasting whole blood could be the sample of choice in epidemiologic studies because of its ability to predict intake, its accessibility, and minimum sample processing.

n-3 Fatty acids consumed from fish and risk of atrial fibrillation or flutter: the Danish Diet, Cancer, and Health Study

BACKGROUND

Experimental studies have shown that n-3 polyunsaturated fatty acids in fish may have antiarrhythmic properties.

OBJECTIVE

We examined the association between consumption of n-3 fatty acids from fish and risk of atrial fibrillation or flutter.

DESIGN

In a prospective cohort study of 47 949 participants (mean age: 56 y) in the Danish Diet, Cancer, and Health Study, we investigated the relation between the consumption of n-3 fatty acids from fish estimated from a detailed semiquantitative food questionnaire and risk of atrial fibrillation or flutter. The subjects were followed up in the Danish National Registry of Patients for the occurrence of atrial fibrillation or flutter and in the Danish Civil Registration System (vital status and emigration). The consumption of n-3 fatty acids from fish was analyzed as sex-specific quintiles with the use of Cox proportional hazards models.

RESULTS

During follow-up (x: 5.7 y), atrial fibrillation or flutter had developed in 556 subjects (374 men and 182 women). When the lowest quintile of n-3 fatty acids consumed from fish was used as a reference, the unadjusted hazard rate ratios in quintiles 2, 3, 4, and 5 were 0.93, 1.11, 1.10, and 1.44, respectively (P for trend = 0.001). The corresponding adjusted hazard rate ratios were 0.86, 1.08, 1.01, and 1.34 (P for trend = 0.006). Inclusion of information on the frequency of fatty fish consumption did not alter these associations.

CONCLUSIONS

Consumption of n-3 fatty acids from fish was not associated with a reduction in risk of atrial fibrillation or flutter. We cannot exclude the possibility of residual confounding caused by a lack of information on intake of fish-oil tablets.

Fish Intake Is Positively Associated with Breast Cancer Incidence Rate

Animal studies have, in general, been supportive of a protective effect of fish and fish (n-3) PUFA against breast cancer risk; but the epidemiologic evidence of such a relationship is limited. Case-control and cohort studies have rarely shown significant associations. The association between total fish intake and the effect of fat content and preparation method of the fish, in relation to the incidence rate ratios of breast cancer, were investigated among postmenopausal women. We also investigated the effect of fish intake with respect to estrogen receptor expression of breast cancer tumors. A total of 23,693 postmenopausal women from the prospective study "Diet, Cancer and Health" were included in the study. During follow-up, 424 women were diagnosed with breast cancer. The incidence rate ratio (IRR) and 95% CI per each additional 25 g of mean daily intake of fish were 1.13 (CI, 1.03-1.23). Analysis of fatty fish gave IRR of 1.11 (CI, 0.91-1.34), and the result for lean fish was 1.13 (CI, 0.99-1.29). When fish intake was stratified into three types of preparation methods, the IRR for fried fish was 1.09 (CI, 0.95-1.25), for boiled fish 1.09 (CI, 0.85-1.42), and for processed fish 1.12 (CI, 0.93-1.34). The IRR per additional 25 g of mean daily intake of fish was 1.14 (CI, 1.03-1.26) for estrogen receptor-positive (ER+) and 1.00 (CI, 0.81-1.24) for estrogen receptor-negative (ER-) breast cancer. In conclusion, this study showed that higher intakes of fish were significantly associated with higher incidence rates of breast cancer. The association was present only for development of ER+ breast cancer.

Comparison of adipose tissue fatty acids with dietary fatty acids as measured by 24-hour recall and food frequency questionnaire in Black and White Adventists: the Adventist Health Study

PURPOSE

To calibrate and compare intake of different fats and individual fatty acids as assessed with a food frequency questionnaire (FFQ) against that estimated with (i) a series of dietary recalls and; (ii) the relative fat concentration in an adipose tissue biopsy. The FFQ was specially designed for use in a cohort of Seventh-day Adventists. In preparation for a large cohort study investigating the effect of diet on risk of colon, prostate and breast cancer.

METHODS

The association of adipose tissue fatty acids and dietary fat intake was assessed in 49 black and 72 white Seventh-day Adventists subjects using 8 different 24-hour recalls, a 200-item food frequency questionnaire (FFQ) and adipose tissue biopsies from each subject.

RESULTS

Pearson correlation between fatty acids in adipose tissue and dietary intake as assessed by multiple 24-hour recalls were as follows: Linoleic acid: 0.77 in black and 0.71 in white subjects, respectively; Linolenic acid: 0.68 (blacks) and 0.62 (whites); Total Polyunsaturated fat (PUFA): 0.78 (blacks) and 0.70 (whites); Total Monounsaturated fat (MUFA): 0.35 (blacks) and 0.03 (whites); Total Saturated fat (SFA): 0.46 (blacks) and 0.56 (whites). Correlations between fatty acids in adipose tissue and dietary intake as assessed by FFQ were: Linoleic acid: 0.61 (blacks) and 0.52 (whites), respectively; Linolenic acid: 0.29 (blacks) and 0.49 (whites); PUFA: 0.62 (blacks) and 0.53 (whites); MUFA: 0.07 (blacks) and 0.31 (whites), SFA: 0.21 (blacks) and 0.31 (whites).

CONCLUSIONS

Our study confirms findings of others that 24-hour recalls are valid for assessing dietary intake of different types of fat. The FFQ we developed and used in this study gave reasonably valid measures of fatty acid intake in our population and is thus suitable for use in large cohort studies. It had validity comparable to that observed for other FFQs.

Smoking as a determinant of high organochlorine levels in Greenland

The authors investigated the accumulation of organochlorines among smoking and nonsmoking Inuit hunters (n = 48) in Uummanaq, Greenland, a population with high dietary exposure to persistent organic pollutants (POPs). Human plasma organochlorine levels were positively correlated with age, marine diet, and smoking or plasma cotinine in multiple linear-regression models (p < 0.001). Body mass index was inversely correlated with organochlorine accumulation, independent of smoking status. These findings confirm that the source of POPs among the Inuit in Greenland is diet, but smoking is an important determinant of POP bioaccumulation. Smoking cessation may provide a means to lower the body burden of POPs.

Variability of fish consumption within the 10 European countries participating in the European Investigation into Cancer and Nutrition (EPIC) study

OBJECTIVE

To describe and compare the consumption of total fish (marine foods) and the fish sub-groups - white fish, fatty fish, very fatty fish, fish products and crustacea, in participants from the European Investigation into Cancer and Nutrition (EPIC) study.

DESIGN

Cross-sectional analysis of dietary intake using a computerised standardised 24-hour recall interview. Crude means, means and standard errors adjusted by age, season and day of the week were calculated, stratified by centre and gender.

SETTING

Twenty-seven redefined centres in the 10 European countries participating in the EPIC study.

SUBJECTS

In total, 35 955 subjects (13 031 men and 22 924 women), aged 35-74 years, selected from the main EPIC cohort.

RESULTS

A six- to sevenfold variation in total fish consumption exists in women and men, between the lowest consumption in Germany and the highest in Spain. Overall, white fish represented 49% and 45% of the intake of total fish in women and men, respectively, with the greatest consumption in centres in Spain and Greece and the least in the German and Dutch centres. Consumption of fatty fish reflected that of total fish. However, the greatest intake of very fatty fish was in the coastal areas of northern Europe (Denmark, Sweden and Norway) and in Germany. Consumption of fish products was greater in northern than in southern Europe, with white fish products predominating in centres in France, Italy, Spain, The Netherlands and Norway. Intake of roe and roe products was low. The highest consumption of crustacea was found in the French, Spanish and Italian centres. The number of fish types consumed was greater in southern than in northern Europe. The greatest variability in consumption by day of the week was found in the countries with the lowest fish intake.

CONCLUSIONS

Throughout Europe, substantial geographic variation exists in total fish intake, fish sub-groups and the number of types consumed. Day-to-day variability in consumption is also high.

Adipose tissue biomarkers of fatty acid intake

BACKGROUND

Biomarkers can provide a more accurate measure of long-term intake than can dietary questionnaires.

OBJECTIVE

The objective was to identify which adipose tissue fatty acids are suitable biomarkers of intake as assessed with a validated food-frequency questionnaire.

DESIGN

Costa Rican men with a mean (+/- SD) age of 56 +/- 11 y (n = 367) and women aged 60 +/- 10 y (n = 136) completed a 135-item food-frequency questionnaire and provided an adipose tissue sample. Fifty fatty acids were identified by capillary gas chromatography. Correlation coefficients were calculated after adjustment for age, sex, body mass index, and smoking status.

RESULTS

The best adipose tissue marker for total intake of saturated fatty acids was 15:0 + 17:0 (r = 0.18). Both 15:0 and 17:0 were also the best correlates of dairy product intake (r = 0.31 for each). The diet-adipose tissue correlations for n-3 fatty acids were r = 0.34 for 18:3, r = 0.15 for 20:5, and r = 0.18 for 22:6. Fish intake correlated significantly with these adipose tissue n-3 fatty acids. Dietary and adipose tissue n-6 fatty acids were highly correlated: 18:2 (r = 0.58) and 18:3 (r = 0.24). The best indicators of total trans fatty acid intake were ct18:2n-6 and tc18:2n-6 (r = 0.58 for each); total 18:1 trans fatty acid (r = 0.45) and 16:1 trans fatty acid (r = 0.16) were the next best indicators.

CONCLUSIONS

Adipose tissue is a suitable biomarker of dietary fatty acid intake, particularly for n-3 and n-6 cis polyunsaturated fatty acids and trans fatty acids. Ideally, adipose tissue and dietary questionnaires should complement, rather than substitute for, each other in epidemiologic studies.

Fluctuations in human milk long-chain PUFA levels in relation to dietary fish intake

Within the Danish population, milk DHA (22:6n-3) levels vary by more than a factor of 10. This paper deals with fluctuations in the milk content of 22:6n-3 and other long-chain PUFA (LCPUFA) and the acute effects of fish meals and fish oil supplements on milk levels of LCPUFA. Twelve fish-eating mothers with 4-mon-old infants provided one blood and one adipose tissue sample, and seven consecutive morning hind-milk samples with dietary records from the previous days. Another 12 lactating women were given fish oil (2-8 g) for breakfast and delivered 6-12 milk samples during the following 24 h. The mean milk 22:6n-3 content of the fish-eating mothers was 0.57+/-0.28 FA% (= percentage of total area of FAME peaks in GLC) and the day-to-day variation (SD/mean) within the individual was 35+/-17%. Mean milk 22:6n-3 content on mornings with no fish the day before was 0.42+/-0.15 FA%; this was increased by 82+/-17% (n = 9, P = 0.05) if the mother had eaten fatty fish. Fish oil resulted in a twofold increase in milk 22:6n-3 levels, which peaked after 10 h and lasted for 24 h. The EPA content of milk was also increased by fish meals and fish oil supplements, but these had no effect on the level of arachidonic acid. The study showed that diurnal and day-to-day fluctuations in levels of milk n-3 LCPUFA are large, which makes it difficult to assess the 22:6n-3 intake of breast-fed infants from a single milk sample. In studies of the functional outcome of dietary 22:6n-3 in breast-fed infants it is suggested also to use a measure of maternal 22:6n-3 status.

Assessment of intake from the diet

Exposure assessment is one of the key parts of the risk assessment process. Only intake of toxicologically significant amounts can lead to adverse health effects even for a relatively toxic substance. In the case of chemicals in foods this is based on three major aspects: (i) how to determine quantitatively the presence of a chemical in individual foods and diets, including its fate during the processes within the food production chain; (ii) how to determine the consumption patterns of the individual foods containing the relevant chemicals; (iii) how to integrate both the likelihood of consumers eating large amounts of the given foods and of the relevant chemical being present in these foods at high levels. The techniques used for the evaluation of these three aspects have been critically reviewed in this paper to determine those areas where the current approaches provide a solid basis for assessments and those areas where improvements are needed or desirable. For those latter areas, options for improvements are being suggested, including, for example, the development of a pan-European food composition database, activities to understand better effects of processing on individual food chemicals, harmonisation of food consumption survey methods with the option of a regular pan-European survey, evaluation of probabilistic models and the development of models to assess exposure to food allergens. In all three areas, the limitations of the approaches currently used lead to uncertainties which can either cause an over- or underestimation of real intakes and thus risks. Given these imprecisions, risk assessors tend to build in additional uncertainty factors to avoid health-relevant underestimates. This is partly done by using screening methods designed to look for "worst case" situations. Such worse case assumptions lead to intake estimates that are higher than reality. These screening methods are used to screen all those chemicals with a safe intake distribution. For chemicals with a potential risk, more information is needed to allow more refined screening or even the most accurate estimation. More information and more refined methods however, require more resources. The ultimate aims are: (1) to obtain appropriate estimations for the presence and quantity of a given chemical in a food and in the diet in general; (2) to assess the consumption patterns for the foods containing these substances, including especially those parts of the population with high consumption and thus potentially high intakes; and (3) to develop and apply tools to predict reliably the likelihood of high end consumption with the presence of high levels of the relevant substances. It has thus been demonstrated that a tiered approach at all three steps can be helpful to optimise the use of the available resources: if relatively crude tools - designed to provide a "worst case" estimate - do not suggest a toxicologically significant exposure (or a relevant deficit of a particular nutrient) it may not be necessary to use more sophisticated tools. These will be needed if initially high intakes are indicated for at least parts of the population. Existing pragmatic approaches are a first crude step to model food chemical intake. It is recommended to extend, refine and validate this approach in the near future. This has to result in a cost-effective exposure assessment system to be used for existing and potential categories of chemicals. This system of knowledge (with information on sensitivities, accuracy, etc.) will guide future data collection.

Adipose fat quality vs. quantity: relationships with children's serum lipid levels

BACKGROUND

There is a controversy as to the relative importance of obesity vs quality of dietary fat in the prediction of serum lipoproteins in children. A reason for this is an apparent lack of studies implementing biomarkers of long-term dietary fat intake among children. The objective of the present study was to assess the relative contribution of degree of obesity, fat centrality, and quality of adipose tissue fat in the prediction of serum lipids in 12-year-old children.

METHODS

Pupils came from 40 schools randomly selected among 541 primary schools in three different provinces of the island of Crete. One thousand forty-six pupils were examined at age 6. At age 9, a representative sample from the original cohort (n = 579) was randomly selected for reevaluation. At the age of 12, a representative sample of 831 pupils was reexamined. At ages 6, 9, and 12, serum lipid measures were obtained from 941, 458, and 791 children, respectively. At age 12, data were obtained on pupils' anthropometry, serum lipids, dietary intake, physical fitness, and physical activity. Adipose tissue fatty acid data were obtained from a subsample of 194 children at age 12.

RESULTS

Regression analyses indicated that children's serum triglycerides related positively to body mass index and waist-hip ratio (WHR). Serum HDL-C related negatively to WHR and positively to endurance run test, an index of physical fitness. Dietary fatty acids, assessed by a single administration of 3-day weighed-food records, did not relate to serum lipids. However, serum HDL-C related negatively to sum of adipose polyunsaturated fatty acids, a measure of long-term polyunsaturated fat intake.

CONCLUSIONS

It appears that obesity and fat centrality are stronger predictors of children's serum lipids than the quality of long-term dietary fat intake or adipose tissue fatty acid composition. It is possible that this finding may relate to the particular subcutaneous depot studied. It is suggested that future studies study abdominal rather than buttock adipose tissue fatty acid composition in relation to children's serum lipid levels.

Site-specific differences in the fatty acid composition of abdominal adipose tissue in an obese population from a Mediterranean area: relation with dietary fatty acids, plasma lipid profile, serum insulin, and central obesity

BACKGROUND

Abdominal obesity is associated with coronary risk, although causality is not well established.

OBJECTIVE

In an obese Mediterranean population, we measured the fatty acid composition of adipose tissue, its relation with dietary fatty acids and central fat deposition, and its influence on plasma lipids and insulin.

DESIGN

Adipose tissue samples were obtained from 84 obese patients (29 men, 55 women) aged 30-70 y (body mass index, in kg/m(2): 27-35). We measured concentrations of insulin and lipids in plasma and fatty acids in subcutaneous, omental, and perivisceral fat. Dietary fatty acid intake was assessed with a 7-d diet record.

RESULTS

The population studied was normolipidemic and normoinsulinemic. There were important differences in fatty acid composition between tissue sites: saturated fatty acids were higher and monounsaturated fatty acids were lower in perivisceral than in subcutaneous fat (P < 0.05). Significant correlations were found for oleic, linoleic, alpha-linolenic, and total n-6 polyunsaturated fatty acids between the subject's habitual diet and adipose tissue composition. Oleic and n-3 fatty acids from adipose regions were negatively correlated with apolipoprotein B and triacylglycerols; adipose tissue 22:1n-9, 20:2n-6, stearic acid, and eicosapentaenoic acid were positively correlated with HDL and apolipoprotein A; and adipose tissue myristic acid was negatively correlated with apolipoprotein A (P < 0.05). Central obesity was positively associated with n-6 polyunsaturated fatty acids and inversely associated with monounsaturated fatty acids and n-3 polyunsaturated fatty acids in adipose tissue (P < 0.05).

CONCLUSION

The differences found in the composition and metabolism of perivisceral, omental, and subcutaneous fats may indicate that their atherogenic capacities also differ.

Single measurement of serum phospholipid fatty acid as a biomarker of specific fatty acid intake in middle-aged Japanese men

OBJECTIVE

To assess the utility of serum phospholipid fatty acid (FA) levels as a biochemical indicator of habitual dietary fatty acid intake in Japanese, whose diet is characterized by low fat intake and high intake of n-3 polyunsaturated fatty acids (PUFA) of marine origin.

SUBJECTS AND METHODS

Eighty-seven male volunteers from four public health center districts that were part of the Japan Public Health Center based Prospective Study (JPHC Study) cohort I, were included in this study. Habitual intake of fatty acid was obtained by 7 day weighed dietary records four times (in one area only twice) in 1994--1995. Blood was collected twice, in February and August of the same year, and the composition of FA in serum phospholipid was analyzed by gas chromatography. The correlation coefficient between serum phospholipid FA levels and fatty acid intake was calculated.

RESULTS

High correlations were observed for eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA), which are marine origin n-3 PUFA (r=0.75, 0.49, 0.50, respectively). No significant correlation was observed for saturated fatty acid (SFA), although the monounsaturated fatty acid (MUFA), palmitoleic acid and oleic acid intake were moderately correlated (r=0.22, 0.35, respectively). The correlations for EPA, DPA and DHA were similar in both samples collected in February and August.

CONCLUSIONS

These data suggest that in populations with a high and stable over time intake of n-3 PUFA of marine origin, a single measurement of serum phospholipids reflects the ranking of habitual intake of marine origin n-3 PUFA.

Selective mobilisation of fatty acids from human adipose tissue

Background: Adipose tissue is a storage organ for dietary fat. During fasting, fatty acids are released into serum as free fatty acids (FFA). Experimental studies indicate that fatty acids are selectively mobilised from adipose tissue into serum. The aim of this study was to investigate whether the composition of the serum FFA fraction reflects selective mobilisation in the fasting state in humans. Methods: The fatty acid composition of fasting serum FFA and adipose tissue were analysed from 112 patients with myocardial infarction and 107 healthy control subjects using gas-liquid chromatography. The subjects' habitual diet was analysed using a food-frequency questionnaire. Results: Significant correlations were found between serum FFA and adipose tissue, particularly for the percentage content of linoleic acid (r=0.73), eicosapentaenoic acid (r=0.68), alpha-linolenic acid (r=0.67) and palmitoleic acid (r=0.60). Percentage contents of palmitic, stearic, linoleic, alpha-linolenic, eicosapentaenoic and docosahexaenoic acid were higher in serum FFA than in adipose tissue, whereas oleic and palmitoleic acid were relatively more abundant in adipose tissue. This may indicate that the former group of fatty acids is preferentially mobilised from adipose tissue into serum. High correlations for polyunsaturated fatty acids were observed between percentage contents of dietary and adipose tissue fatty acids. The correlation of fatty acids between diet and serum FFA was weak, but a tendency towards higher correlations for polyunsaturated fatty acids was observed. Conclusions: Our findings are compatible with the hypothesis that, in the fasting state, fatty acids are selectively mobilised from adipose tissue into serum FFA.

Fatty acid composition of adipose tissue and serum lipids are valid biological markers of dairy fat intake in men

The fatty acid intake is in part reflected by the fatty acid composition of adipose tissue and serum lipids. We evaluated whether the proportions of myristic (14:0), pentadecanoic (15:0) and heptadecanoic (17:0) fatty acids in the adipose tissue triacylglycerols and serum cholesterol esters and phospholipids reflect long-term dairy fat consumption in free-living men. In 114 healthy men aged 40-76 y, we compared the relative content of 14:0, 15:0 and 17:0 in subcutaneous adipose tissue and in serum lipids with relative intake (g/100 g of total fat) assessed by two 1-wk weighed food records made 6 mo apart and assessed by fourteen 24-h dietary recall interviews equally distributed during 1 y. According to food records, the mean +/- SD dairy fat intake was 24.9 +/- 13.1 g/d (29.6 +/- 10.5 g/100 g total fat); intake of 14:0, 15:0 and 17:0 was 4.6, 0.23 and 0.16 g/100 g total fat, and the content in adipose tissue was 3.6, 0.36 and 0.25 g/100 g fatty acids, respectively. Pearson correlation coefficients between intake of dairy fat (based on 24-h recalls) and fatty acid composition of adipose tissue were 0.64 (P: < 0.001) for 14:0, 0.74 (P: < 0.001) for 15:0 and 0.60 (P: < 0.001) for 15:0 + 17:0. Corresponding correlations with serum cholesterol esters were 0.34 (P: < 0.001) (14:0), 0.45 (P: < 0.001) (15:0) and 0.56 (P: < 0.001) (15:0 + 17:0), and with serum phospholipids the values were 0.30 (P: < 0.01) (14:0), 0.50 (P: < 0.001) (15:0) and 0.50 (P: < 0.001) (15:0 plus 17:0). In our study population, the relative content of 15:0 or 14:0 in adipose tissue is a valid biomarker for long-term dairy fat intake in free-living individuals. When adipose tissue is not available, 15:0 content in serum cholesterol esters or phospholipids might be used. Intake data based on repeated 24-h recalls are equally informative and may be an equivalent choice in nutritional studies.

Uptake of individual fatty acids into adipose tissue in relation to their presence in the diet

BACKGROUND

The fatty acid composition of adipose tissue triacylglycerol reflects, but is not identical to, the fatty acid composition of the habitual diet.

OBJECTIVE

We investigated whether the fatty acid composition of adipose tissue is explained by differences between fatty acids in early storage in adipose tissue after a meal.

DESIGN

Nine healthy men ate a meal containing several fatty acids. Blood samples were taken for 6 h after the meal from an arterialized hand vein and a vein draining the anterior abdominal subcutaneous adipose tissue.

RESULTS

Net storage of fatty acids in adipose tissue occurred between 1 and 4 h after the meal. In relation to the amount fed, storage of fatty acids differed (P < 0. 01) between classes (n-3 polyunsaturated < saturated < n-6 polyunsaturated < monounsaturated); oleic acid was stored in the greatest amounts. These differences agreed closely with published data, except for n-3 polyunsaturated fatty acids. The only individual metabolic step at which significant differences between fatty acids was shown was incorporation of fatty acids into chylomicron triacylglycerol. Differences between fatty acids in rate of extraction from chylomicron triacylglycerol and net uptake into adipose tissue in the postprandial period were significant (P < 0. 01), but not when expressed in relation to proportions in chylomicron triacylglycerol.

CONCLUSIONS

The characteristic fatty acid pattern of adipose tissue may predominantly reflect the early metabolic handling of different fatty acids. Adipose tissue uptake of n-3 polyunsaturated fatty acids is slow in relation to that of other fatty acids.

Assessment of individual fatty acid intake

Dietary assessment of individual fatty acid intake is difficult due to a number of limitations. Information regarding the type, quantity and brand-name of fat used in cooking and at the table is required. In addition, margarine manufacturers may change the component oils used for reasons of cost, which changes the fatty acid composition of their products from season-to-season. Independent markers of fatty acid intake are required, therefore, to compensate for these limitations. Adipose tissue concentrations have been used as a measure of habitual intake of fatty acid groups and individual fatty acids in numerous studies. Saturated (SFA) and monounsaturated fatty acids (MUFA) are generally poorly correlated with adipose tissue concentrations, which can be explained partly by endogenous synthesis. In general, adipose tissue concentrations of exogenously-produced fatty acids (n-3 and n-6 polyunsaturated fatty acids (PUFA)) are well correlated with estimates of habitual intake. Correlations between dietary trans unsaturated fatty acids (TUFA) and adipose tissue concentrations vary between countries, which may be due to differences in dietary sources. Correlations may be affected by differences in bioavailability or selective retention of fatty acids in certain tissue lipids.

Diet as a risk factor for the development of ulcerative colitis

OBJECTIVE

Dietary factors have been considered as a possible risk factor for ulcerative colitis (UC). However, available data are inconsistent. The aim of the present study was to evaluate the etiological role of dietary factors in the development of UC.

METHODS

Recently diagnosed (<6 Months) UC patients (n = 43) and age- and gender-matched population controls (n = 43) were studied in a case-control design. The crosscheck dietary history method was used to assess dietary intake of 5 yr before the study. Adipose tissue fatty acid composition was used as a biomarker of long-term fat intake. Conditional logistic regression-derived odds ratios (OR), and 95% confidence intervals (CI) were used for statistical analysis. Dietary intake ORs were adjusted for energy intake.

RESULTS

High intakes of monounsaturated fat (OR: 33.9 [95% CI 2.6-443.1]), polyunsaturated fat (OR: 5.1 [95% CI 1.0-26.7]), and vitamin B6 (OR: 6.9 [95% CI 1.6-30.7]) were associated with an increased risk to develop UC. No other significant associations were found with UC risk.

CONCLUSIONS

High intakes of mono- and polyunsaturated fat and vitamin B6 may enhance the risk of developing UC. Whether this observation is a true risk factor in the development of UC or rather a reflection of a certain dietary lifestyle needs to be investigated.

Low alpha-linolenic acid content of adipose breast tissue is associated with an increased risk of breast cancer

Data derived from experimental studies suggest that alpha-linolenic acid may have a protective effect in breast cancer. Observations obtained from epidemiological studies have not allowed conclusions to be drawn about a potential protective effect of dietary alpha-linolenic acid on breast cancer, possibly because of methodological issues. This case-control study conducted in an homogeneous population from a central area in France was designed to explore the hypothesis that alpha-linolenic acid inhibits breast cancer, using fatty acid levels in adipose breast tissue as a biomarker of past qualitative dietary intake of fatty acids. Biopsies of adipose breast tissue at the time of diagnosis were obtained from 123 women with invasive non-metastatic breast carcinoma. 59 women with benign breast disease served as controls. Individual fatty acids were analysed by capillary gas chromatography. An unconditional logistic regression model was used to obtain odds ratio estimates whilst adjusting for age, menopausal status and body mass index (BMI). No association was found between fatty acids (saturates, monounsaturates, long-chain polyunsaturates n-6 or n-3) and the disease, except for alpha-linolenic acid which showed an inverse association with the risk of breast cancer. The relative risk of breast cancer for women in the highest quartile of adipose breast tissue alpha-linolenic acid level was 0.36 (95% confidence interval=0.12-1.02) compared with those in the lowest quartile (P trend=0.026), suggesting a protective effect of alpha-linolenic acid in the risk of breast cancer. The effects of dietary alpha-linolenic on the risk of breast cancer warrant further study.

Selectivity of fatty acids on lipid metabolism and gene expression

Triacylglycerols represent the main form of storage for a wide spectrum of fatty acids. Their utilization first involves mobilization from adipose tissue through lipolysis. The release of individual fatty acids from adipose tissue is selective in vitro and in vivo in animal studies and also in human subjects. Generally, fatty acids are more readily mobilized from fat cells when they are short-chain and unsaturated. This selectivity could affect the storage of individual fatty acids in adipose tissue, and their subsequent supply to tissues. The nature of the dietary fats could affect lipid homeostasis and body fat deposition. Dietary fish oil influences adipose tissue development in a site-specific manner as a function of diet and feeding period. A diet high in n-3 polyunsaturated fatty acids (PUFA) results in a preferential partitioning of ingested energy towards oxidation at the expense of storage. Fatty acids are important mediators of gene expression in the liver. Indeed, genes encoding both glycolytic and lipogenic enzymes and key metabolic enzymes involved in fatty acid oxidation are regulated by dietary PUFA. White adipose tissue could also be a target for PUFA control of gene expression. The treatment of pre-adipose cells by fatty acids induces the expression of numerous genes that encode proteins involved in fatty acid metabolism. The mechanisms of PUFA-mediated repression of gene expression in adipocytes seem to be different, at least partly, from those described in liver. Tissue-specific and site-specific factors are possibly involved in the specific effect of PUFA on gene expression, although other mechanisms cannot be excluded.

Relation between the intake of milk fat and the occurrence of conjugated linoleic acid in human adipose tissue

BACKGROUND

Conjugated linoleic acid (CLA) is a group of naturally occurring fatty acids mainly present in fats from ruminants. CLA has been shown to be a potential anticarcinogen.

OBJECTIVE

In this study, the relation between bovine milk fat intake and the occurrence of CLA in human adipose tissue was investigated.

DESIGN

One hundred twenty-three men weighed and recorded the foods they consumed for 1 wk. Afterward, recall interviews were conducted by telephone monthly for 7 consecutive months to inquire about food consumption during the previous 24 h. The entire dietary recording procedure was repeated once. The fatty acid composition of adipose tissue and serum was analyzed.

RESULTS

The average amount of one isomer of CLA--9-cis,11-trans-octadecadienoic acid (9c,11t-18:2)--as a percentage of total fatty acids was found to be 0.50% in adipose tissue and 0.25% in serum. The amount of 9c,11t-18:2 in adipose tissue was significantly correlated with milk fat intake (r = 0.42). The percentage of 9c,11t-18:2 in both adipose tissue and in serum was strongly correlated with myristoleic acid (14:1).

CONCLUSION

The amount of 9c,11t-18:2 in human adipose tissue was significantly related to milk fat intake.

An optimized method for fatty acid analysis, including quantification of trans fatty acids, in human adipose tissue by gas-liquid chromatography

Considering the need for a quick direct method for measurement of the fatty acid composition including trans isomers of human adipose tissue we have developed a procedure using gas-liquid chromatography (GLC) alone, which is thus suitable for validation of fatty acid status in epidemiological studies. Fatty acids ranging in carbon number from 12 to 22 and with 0-6 double bonds were resolved and identified by capillary column GLC with a temperature program starting at 150 degrees C. Following injection, the oven temperature was increased at a rate of 3 degrees C/min to 200 degrees C, then held constant for 25 min, and finally raised at 25 degrees C/min to 225 degrees C. The trans and cis isomers of 18:1 were well separated from each other, as shown by silver-ion thin-layer chromatography. Verification by standards showed that the trans 18:1 isomers with a double bond in position 12 or lower were separated from the cis 18:1 isomers with a double bond in position 6 or higher. As the adipose tissue samples contained only small amounts of the 13t-, 14t- and 15t-18:1 isomers and the 4c- and 5c-18:1 isomers the overlapping was found to be minimal. The GLC method may also be valuable for determining the fatty acid profiles including total trans in other tissues.

Adipose tissue fatty acids in men from two populations with different cardiovascular risk: the LiVicordia study

The LiVicordia study was set up to investigate possible causes for coronary heart disease mortality in middle-aged Lithuanian men being four times higher than in Swedish men. In a previous part of this study we found lower total and low density lipoprotein (LDL) cholesterol in the Lithuanian men in spite of them having a higher fat intake than in the Swedish men. Their LDL was also more susceptible to oxidation in vitro than was that of the Swedish men. Fat quality can influence LDL oxidation. In order to obtain data on long-term fat quality intake we measured the fatty acid composition of abdominal wall adipose tissue by gas chromatography in men aged 50 years from Vilnius, Lithuania (n=50) and Linköping, Sweden (n=50). Men from Vilnius had a significantly higher percentage of adipose tissue long chain polyunsaturated fatty acids (PUFA) (20:4n6, 20:5n3, 22:5n5, 22:6n3) and lower percentage of saturated fatty acids, especially myristic acid (14:0), 3.4+/-0.7 versus 4.6+/-0.8, p<0.0001. The percentage content of adipose tissue linoleic acid (18:2n6) was 11.5+/-2.1 versus 11.0+/-1.4 (n.s.) and of linolenic acid (18:3n3) 0.7+/-0.3 versus 0.6+/-0.2 (n.s.) in men from Vilnius and Linköping, respectively. It is concluded that the adipose tissue content of essential fatty acids is similar in men from Vilnius and men from Linköping and therefore the intake is also likely to be similar. The higher contents of long chain highly unsaturated fatty acids in men from Vilnius may be of importance in the oxidation process of LDL.

Selective release of human adipocyte fatty acids according to molecular structure

The objective of the present study was to investigate the mobilization of individual fatty acids from human white fat cells. Mammary adipose tissue from eight healthy non-obese women in their normal dietary state was collected, and isolated adipocytes were incubated with lipolytic agents. The mobilization of 34 individual fatty acids was measured by comparing the composition of non-esterified fatty acids (NEFA) with that of the triacylglycerols (TAG) from which they originated through lipolysis. Compared with TAG, NEFA were enriched in some polyunsaturated fatty acids with 18-20 carbon atoms. Conversely, the percentage of very-long-chain (20-22 carbon atoms) saturated and monounsaturated fatty acids was approx. 2 times lower in NEFA than in TAG. The relative mobilization (% in NEFA/% in TAG) of the most readily mobilized fatty acid (C20:5, n-3; 2.25) was more than 6-fold higher than that of the least readily mobilized (C22:1,n-11; 0.37). Relationships were found between the molecular structure of fatty acids and their mobilization rate. For a given chain length, the relative mobilization rate increased with increasing unsaturation, whereas for a given unsaturation, it decreased with increasing chain length. The relative mobilization rate for essential fatty acids decreased in the following order: C20:5,n-3>C20:4,n-6>C18:3,n-3>C18:2, n-6>C22:6,n-3. Interestingly, C20:5,n-3 and C20:4,n-6, which are respectively precursors of the 3- and 2-series of prostaglandins, were preferentially mobilized. It is concluded that fatty acids are selectively mobilized from human fat cells according to molecular structure, in full agreement with animal studies. By modulating the qualitative fatty acid supply to organs and by remodelling the fatty acid composition of adipose tissue, this selectivity would be relevant for consideration in physiology, health and epidemiology.

The effects of feeding suet-enriched chow on site-specific differences in the composition of triacylglycerol fatty acids in adipose tissue and its interactions in vitro with lymphoid cells

The effects of diet on the composition and properties of adipose tissue in relation to lymph nodes were studied in adult guinea-pigs. The proportions of monoenoic triacylglycerol fatty acids were constant in all sites in adipose tissue of similarly fed guinea-pigs, but were substantially greater in samples from guinea-pigs fed on suet-enriched chow. Triacylglycerols in adipose tissue from near nodes contained significantly fewer saturated fatty acids, and significantly more 18:2n-6 and 18:3n-3 than those in samples from sites remote from nodes within the same depot. Depots that interact most strongly with lymphoid cells in vitro had the largest and most consistent within-depot differences. The gradients of triacylglycerol fatty acid composition with distance from lymph nodes in two small intermuscular depots were similar in guinea-pigs fed on plain or suet-enriched chow. These findings are consistent with the hypothesis that adipose tissue around lymph nodes is specialized for local interactions with the lymphoid cells therein, and help to explain the variability of serial or duplicate measurements of adipose tissue composition. When cultured alone, lipopolysaccharide-stimulated lymph node lymphoid cells from suet-fed guinea-pigs incorporated as much labelled thymidine as the controls. Adipose tissue explants from suet-fed guinea-pigs inhibited lymphocyte proliferation much less than those of the controls, although the site-specific differences were similar. The pattern of site-specific differences in glycerol released from explants incubated alone was generally similar for both dietary groups, but except in the popliteal depot, the increases following co-culturing with lymphoid cells were smaller for samples from suet-fed guinea-pigs. These experiments show that minor changes in the fatty acid composition of the diet can substantially alter the interactions between adipose tissue and lymphoid cells.

Linoleic and alpha-linolenic acids differently modify the effects of elaidic acid on polyunsaturated fatty acid metabolism and some immune indices in rats

To explore whether the metabolic responses to trans, compared with cis, fatty acids depend on the source of dietary polyunsaturated fatty acids (PUFA), male Sprague-Dawley rats, 5 weeks old, were fed on diets containing 30 g oleic (cis) or elaidic (trans) acids/kg in combination with either 70 g perilla oil (alpha-linolenic acid) or safflowerseed oil (linoleic acid)/kg for 3 weeks in separate experiments. The dietary fats were adjusted to have the same level of total PUFA. The dietary manipulation did not influence the growth indices, but spleen weight was greater when the dietary PUFA source was perilla oil. The incorporation of trans fatty acid into liver phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine and adipose tissue lipids, particularly phospholipids, was significantly higher when rats were fed on safflowerseed oil compared with perilla oil. However, only limited differences were observed in the effects of cis and trans fatty acids on the proportions of PUFA in liver phospholipids. Splenic production of prostaglandin E2 was reduced by trans fatty acid when safflowerseed oil was the PUFA source, but no trans effect was observed on leukotriene C4 production. Dietary PUFA significantly influenced the concentration of plasma immunoglobulins (Ig) but the effect of geometry was only seen in IgG which was increased by trans acid. Dietary trans fatty acid increased the CD4+:CD8+ T-lymphocyte ratio in the spleen, reflecting a decreasing trend of the proportion of CD8+, when combined with perilla oil. These observations indicate that the type of PUFA simultaneously ingested specifically influences the effect that trans acid exerts on PUFA metabolism, eicosanoid production and some immune indices.

Reproducibility and relative validity of a self-administered semiquantitative food frequency questionnaire applied to younger women

We have evaluated the reproducibility and relative validity of a semiquantitative food frequency questionnaire (FFQ) used in a prospective study of risk factors for cervical neoplasia. The questionnaire is a modified version of one developed and evaluated in a middle-aged Danish population. In the present study, 122 women from the general population of Copenhagen, aged 20-29 years, completed the FFQ twice at a 1-year interval, and provided three 4-day dietary records during the intervening year. The mean nutrient intakes calculated from the first and second questionnaire were similar and, for most nutrients, close to those obtained from the dietary records. The Pearson correlation coefficients between the mean nutrient intakes from the two questionnaires ranged from 0.53 (95% CI, 0.39-0.65) for vitamin E to 0.76 (95% CI, 0.67-0.83) for vitamin B12 (median, 0.67 [95% CI, 0.56-0.76]). In comparisons between the second FFQ and the dietary records, the correlations ranged from 0.24 (95% CI, 0.07-0.40) for vitamin D to 0.63 (95% CI, 0.51-0.73) for sucrose (median, 0.42 [95% CI, 0.26-0.561). The correlations between FFQ and dietary records were generally higher after adjustment for energy intake (median, 0.53 [95% CI, 0.39-0.65]) and within-person variability (median, 0.64 [95% CI, 0.52-0.73]). On average, 71% of the women were classified in the same (+/- 1) quintile in the second FFQ and the dietary records. An average of 3.8% of the women were grossly misclassified into the highest and lowest quintiles by the dietary records. The relative validity of the FFQ in this population was similar to that reported earlier. It is concluded that the FFQ is reproducible and provides a useful scale for categorizing individuals according to their intake of energy and nutrients.

An in 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 applied 13C 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 of 13C 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.

Age-related changes in the percentage of oleate in adipose tissue of male and female Fischer rats

Fischer 344 rats showed sex difference in the percentage of oleate in lipids of the omental adipose tissue (Thorling, E.B. and Overvad, K. (1994) Nutr. Res. 14, 569-576). The development of this difference was studied with respect to time in rats maintained on laboratory chow, from the age of 3 weeks to 20 weeks. From the age of 3 weeks to 5 weeks the percentage of oleate increased slightly in both sexes. From the age of 5 weeks to 13 weeks the percentage (mean +/- S.D., n = 5) increased further in the female rats from 24.8 +/- 0.6% to 27.6 +/- 0.6%, whereas in the male rats it dropped from 22.9 +/- 0.4% to 20.2 +/- 0.6% at the same time points, respectively. In adult rats, age 20 weeks, the percentage of oleate was 28.6 +/- 0.3% and 19.6 +/- 0.5% for females and males, respectively. Castrated males partly maintained their juvenile level, being 21.1 +/- 1.1% fourteen weeks after castration at the age of 6 weeks. Oestrogen injections twice a week to the castrated rats increased their oleate percentage within the same period to 23.4 +/- 0.3%, partly reflecting the increase observed in the female rats. Stearic acid showed similar but less pronounced changes. The ratio oleic acid/stearic acid was constantly higher in the female than in the male rats, and this difference increased with age. The results of the present study suggest that these changes in percentage of oleate in adipose tissue lipids may partly have been caused by an effect of sex steroids on the delta-9-desaturase.

Fatty acid composition of adipose tissue in humans. Implications for the dietary fat-serum cholesterol-CHD issue

Interest in studies of the fatty acid composition of adipose tissue has arised from the dietary fat-serum cholesterol-CHD issue. The fatty acid composition of depot fat reflects that of the diet. Gas chromatography analysis of subcutaneous adipose tissue yield objective and reliable information of the fatty acid composition of the habitual diet of individuals. A relative linoleic acid deficiency, as depicted by low adipose tissue linoleate levels, has not convincingly been demonstrated to be of importance in the aetiology of atherosclerosis or related disorders. Inverse correlation between n-3 fatty acids and coronary artery disease has been reported. Dietary supplementation of n-3 fatty acids may be of relevance, however the risk of hazardous side-effects do exist. In conclusion, a simple reduction of the total fat content of the diet still seems to be the most important strategy for prevention of atherosclerosis.