Green tea extract only affects markers of oxidative status postprandially: lasting antioxidant effect of flavonoid-free diet

Epidemiological studies suggest that foods rich in flavonoids might reduce the risk of cardiovascular disease and cancer. The objective of the present study was to investigate the effect of green tea extract (GTE) used as a food antioxidant on markers of oxidative status after dietary depletion of flavonoids and catechins. The study was designed as a 2×3 weeks blinded human cross-over intervention study (eight smokers, eight non-smokers) with GTE corresponding to a daily intake of 18·6 mg catechins/d. The GTE was incorporated into meat patties and consumed with a strictly controlled diet otherwise low in flavonoids. GTE intervention increased plasma antioxidant capacity from 1·35 to 1·56 (P<0·02) in postprandially collected plasma, most prominently in smokers. The intervention did not significantly affect markers in fasting blood samples, including plasma or haemoglobin protein oxidation, plasma oxidation lagtime, or activities of the erythrocyte superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase. Neither were fasting plasma triacylglycerol, cholesterol, α-tocopherol, retinol, β-carotene, or ascorbic acid affected by intervention. Urinary 8-oxo-deoxyguanosine excretion was also unaffected. Catechins from the extract were excreted into urine with a half-life of less than 2 h in accordance with the short-term effects on plasma antioxidant capacity. Since no long-term effects of GTE were observed, the study essentially served as a fruit and vegetables depletion study. The overall effect of the 10-week period without dietary fruits and vegetables was a decrease in oxidative damage to DNA, blood proteins, and plasma lipids, concomitantly with marked changes in antioxidative defence.

Sociodemographic differences in dietary habits described by food frequency questions — results from Denmark

OBJECTIVES

To investigate whether a modest number of food frequency questions are sufficient to describe sociodemographic differences in dietary habits, and to identify sociodemographic characteristics of subjects adhering to food-based dietary guidelines operationalised in a "healthy-diet index".

DESIGN

Cross-sectional population survey.

SUBJECTS

A total of 480 men, 515 women, aged 15-90 y. Random sample of private telephone numbers drawn from regional telephone records, geographically stratified. Participation rate 62%.

METHODS

Computer-assisted telephone interviews, including six food frequency questions, a question on type of fat spreads used on bread, questions on seven sociodemographic variables.

RESULTS

The summary of the healthy-diet index showed that the subjects who adhered to food-based dietary guidelines (top quintile) compared to those who did not (bottom quintile) were most often women (odds ratio (OR)=6.07; confidence interval (CI): 3.91-9.43, women vs men), of older age (OR=9.72; CI: 3.02-31.31, old age vs young), highly educated (OR=3.69; CI: 1.53-8.92, high education vs low) and living in multiperson households including children (OR=4.66; CI: 2.47-8.80, multiperson household vs single household). The results also showed that gender difference in dietary habits is associated with other sociodemographic variables.

CONCLUSIONS

The selected food frequency questions proved sufficient to describe sociodemographic differences in dietary habits, and this method may be a valuable supplement to traditional quantitative dietary surveys in monitoring sociodemographic changes in eating patterns. The results also underline the influence of sociodemographic status on dietary habits.

SPONSORSHIP

The Danish Nutrition Council funded the study.

Green tea extract only affects markers of oxidative status postprandially: lasting antioxidant effect of flavonoid-free diet

Epidemiological studies suggest that foods rich in flavonoids might reduce the risk of cardiovascular disease and cancer. The objective of the present study was to investigate the effect of green tea extract (GTE) used as a food antioxidant on markers of oxidative status after dietary depletion of flavonoids and catechins. The study was designed as a 2 x 3 weeks blinded human cross-over intervention study (eight smokers, eight non-smokers) with GTE corresponding to a daily intake of 18.6 mg catechins/d. The GTE was incorporated into meat patties and consumed with a strictly controlled diet otherwise low in flavonoids. GTE intervention increased plasma antioxidant capacity from 1.35 to 1.56 (P<0.02) in postprandially collected plasma, most prominently in smokers. The intervention did not significantly affect markers in fasting blood samples, including plasma or haemoglobin protein oxidation, plasma oxidation lagtime, or activities of the erythrocyte superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase. Neither were fasting plasma triacylglycerol, cholesterol, alpha-tocopherol, retinol, beta-carotene, or ascorbic acid affected by intervention. Urinary 8-oxo-deoxyguanosine excretion was also unaffected. Catechins from the extract were excreted into urine with a half-life of less than 2 h in accordance with the short-term effects on plasma antioxidant capacity. Since no long-term effects of GTE were observed, the study essentially served as a fruit and vegetables depletion study. The overall effect of the 10-week period without dietary fruits and vegetables was a decrease in oxidative damage to DNA, blood proteins, and plasma lipids, concomitantly with marked changes in antioxidative defence.

Monitoring of dietary changes by telephone interviews: results from Denmark

OBJECTIVES

To monitor trends in Danish food habits with respect to selected key elements, from 1995 to 1998, and to evaluate the appropriateness of the method developed for that purpose.

DESIGN AND METHOD

Two cross-sectional population surveys, in 1995 and 1998. Data collection by computer-assisted telephone interviews including 10 food-frequency questions, questions on type of fat used on sandwiches and drinking milk, and check questions on the previous day. Reproducibility was tested in a subgroup (n = 222) in the 1998 survey.

SETTING

The Danish Nutrition Council initiated the survey.

SUBJECTS

Men and women aged 15-90 years, 1007 in 1995 and 1024 in 1998. Samples of private telephone numbers were drawn from regional telephone registers, geographically stratified. Participation rates were 62%.

RESULTS

Significant differences were observed between 1995 and 1998, some of these in accordance with dietary guidelines (decreased use of whole milk and fat spread on bread, increased use of skimmed milk, salad vegetables, rice/pasta and fish). Other changes were opposite to dietary guidelines (increased use of soft butter, decreased use of soft margarine and low-fat spreads, potatoes, and fresh fruit). Differences in average consumption frequency amounted to 4-13%. Several results were confirmed by comparison with other data, and the reproducibility of the method was acceptable. Data were suitable for analysis of food use patterns, a relevant approach when assessing food habits in a lifestyle context.

CONCLUSIONS

The changes observed illustrate the dynamics of food habits and the need for frequent monitoring. This simple telephone method may be a valuable tool for that purpose, as a supplement to national dietary surveys, also in a public health context.

[Polyphenolic antioxidants in fruit juice. Urinary excretion and effects on biological markers for antioxidative status]

This intervention study was designed as cross-over (four women, one man) with three doses of black currant/apple (1:1) juice (750, 1000, and 1500 mL) for one week corresponding to an intake of 4.8, 6.4, and 9.6 mg quercetin per day. Urinary excretion of quercetin increased significantly with dose and with time. The fraction excreted in urine was constant 0.29-0.47%. Plasma quercetin did not change with juice intervention. Plasma ascorbate increased during intervention due to ascorbate from the juice. Total plasma malondialdehyde decreased with time during 1500 mL juice intervention. Plasma protein 2-adipic semialdehyde residues, increased with time and dose, and glutathione peroxidase increased with juice dose, whereas other selected markers of oxidative status did not change. These effects might be related to several components of the juice and cannot be attributed solely to its quercetin content.

[Changes in food habits among the population from 1995 to 1998]

In order to survey trends in food habits the Danish Nutrition Council initiated two food frequency surveys, comprising ten nutritionally important foods, in 1995 and in 1998. Participants were men and women, 15-90 yrs, from similar population samples (n = 1007 in 1995, 1024 in 1998). Participation rate was 62% in 1995 and 63% in 1998. Data were collected by telephone interview. For six of the ten foods significant changes in consumption frequencies were observed: salad/raw vegetables, rice/pasta and fish were consumed more frequently in 1998, whereas consumption of meat, potatoes and fresh fruit had become less frequent. Average frequencies differed by 4-13%. In 1998 low-fat milk had become more common, whereas whole milk was now less common. More subjects now skipped fat spreads on their bread, but more chose spreads containing butterfat. Some, but not all, of the observed changes point in the right direction compared to recommendations. The results demonstrate that food habits are currently in a dynamic process.

Dietary guidelines and patterns of intake in Denmark

Food-based dietary guidelines in Denmark have usually been expressed in simple terms only and need to be elaborated. Quantitative recommendations on fruit and vegetable intake were issued in 1998, recommending 600 g/d (potatoes not included). This paper is based on a national dietary survey in 1995 (n = 3098, age range 1-80 years) supplemented with data from a simple frequency survey in 1995 (n = 1007, age range 15-80 years) and from the first national survey in 1985 (n = 2242, age range 15-80 years). Only data on adults are included in this paper. Fat intake, saturated fat in particular, is too high (median intake 37 %energy and 16 %energy, respectively). Main fat sources are separated fats (butter, margarine, oil, etc.: 40%), meat (18%), and dairy products (21%). Total fat intake decreased from 1985 to 1995 but fatty acid composition did not improve. Dietary fibre intake is from 18 to 22 g/d (women and men, respectively) with 62% from cereals, 24% from vegetables and 12% from fruit. Mean intake of vegetables and potatoes was from 200 to 250 g/d (women and men, respectively). Mean intake of fruit and vegetables (potatoes not included) was 277 g/d, or less than half of the new recommendation (600 g/d). Only 15% of participants in the frequency survey reported consuming both fruit and vegetables every day, and only 28% reported to do so almost every day. In conclusion, dietary intake in Denmark is characterized by a high intake of saturated fat and total fat, and by a relatively low intake of fruit and vegetables.

Effect of fruit juice intake on urinary quercetin excretion and biomarkers of antioxidative status

BACKGROUND

Epidemiologic studies suggest that foods rich in flavonoids might reduce the risk of cardiovascular disease.

OBJECTIVE

Our objective was to investigate the effect of intake of flavonoid-containing black currant and apple juice on urinary excretion of quercetin and on markers of oxidative status.

DESIGN

This was a crossover study with 3 doses of juice (750, 1000, and 1500 mL) consumed for 1 wk by 4 women and 1 man corresponding to an intake of 4.8, 6.4, and 9.6 mg quercetin/d.

RESULTS

Urinary excretion of quercetin increased significantly with dose and with time. The fraction excreted in urine was 0.29-0.47%. Plasma quercetin did not change with juice intervention. Plasma ascorbate increased during intervention because of the ascorbate in the juice. Total plasma malondialdehyde decreased with time during the 1500-mL juice intervention, indicating reduced lipid oxidation in plasma. Plasma 2-amino-adipic semialdehyde residues increased with time and dose, indicating a prooxidant effect of the juice, whereas erythrocyte 2-aminoadipic semialdehyde and gamma-glutamyl semialdehyde concentrations, Trolox-equivalent antioxidant capacity, and ferric reducing ability of plasma did not change. Glutathione peroxidase activity increased significantly with juice dose.

CONCLUSIONS

Urinary excretion of quercetin seemed to be a small but constant function of quercetin intake. Short-term, high intake of black currant and apple juices had a prooxidant effect on plasma proteins and increased glutathione peroxidase activity, whereas lipid oxidation in plasma seemed to decrease. These effects might be related to several components of the juice and cannot be attributed solely to its quercetin content.

[Food consumption of the population. Trends followed via telephone interviews]

This study aimed at establishing and evaluating a simple method for surveilling trends in consumption of 10 nutritionally important foods. The method is based on food frequency questions combined with questions on the previous days intake, collected through telephone interviews. Participants (461 men, 546 women, 15-60+ yrs) came from a population sample. Between 22 and 69% consumed the foods in question as frequently as prescribed by the Danish food recommendations (lowest for fish and for vegetables, highest for potatoes/rice/pasta). Characteristic sex and age differences were observed, similar to findings from traditional, quantitative food surveys in Denmark. The food frequency results were confirmed by results from the previous day's intake. Crossing of frequencies for different foods gave additional information on consumption patterns. The results indicate that this very simple method may be a useful supplement to traditional quantitative dietary surveys for surveilling trends in food consumption. The Danish Nutrition Council therefore aims at doing similar surveys every other year.

Iodine. Do we need an enrichment program in Denmark?

A working group was established to evaluate the need for iodine enrichment in Denmark. Judged from studies of urinary iodine excretion and one dietary survey the intake of iodine in Denmark is low compared with recommended intakes. The occurrence of non-toxic goitre is relatively high; between 9 and 13% in elderly women. Furthermore, a high occurrence of toxic goitre has been seen in the western part of Denmark. On the other hand, an increased or a high intake of iodine may lead to hyperthyroidism and thyroiditis. The working group concluded that an increase in iodine intake in the Danish population is needed and the best way to achieve this is to iodize all salt. To avoid side effects of a sudden large increase in iodine intake the initial amount of iodine in salt will only be 2 ppm.

Biomarkers of habitual fish intake in adipose tissue

The association between habitual fish and marine n-3 polyunsaturated fatty acid (PUFA) intake, and the fatty acid composition of subcutaneous fat was studied in 24 healthy young volunteers. Habitual dietary intakes were estimated from three 7-d weighted food records made at months 0, 5, and 8 of the 8-mo study period. The adipose tissue fatty acid composition of each individual was determined by gas chromatography as the mean of two gluteal biopsies, obtained in the first and the last month of the study. The daily consumption of fish and of marine n-3 PUFAs in absolute terms (g/d) was significantly associated with adipose tissue docosahexaenoic acid content (DHA; r = 0.55 and 0.58, respectively, P < 0.001), but not with eicosapentaenoic and docosapentaenoic acid contents. Our study indicates that the adipose tissue DHA content is the biomarker of choice for the assessment of long-term habitual dietary intakes of fish and marine n-3 PUFAs.

Coronary heart disease risk factors, physical activity, and fitness in young Danes

In a random sample of young Danish adults (86 men and 115 women, 23-27 yr of age) maximal oxygen uptake (VO2max), physical activity (PA), blood pressure, blood lipids, body fat content, and smoking habits were studied. Cholesterol, triglyceride and body fat related negatively to VO2max. The ratio HDL/total cholesterol was positively related to VO2max (r = 0.3, P < 0.001), but no relationship was observed for HDL cholesterol. No association was found between PA and any of the risk factors. The relationships between different measures of PA and directly measured VO2max was around r = 0.3. No relationship existed between heart rate recorded during submaximal testing and PA (r = 0.0), which indicates that the method of assessing VO2max is important in demonstrating relationships to PA and risk factors. In conclusion, a favorable coronary heart disease risk profile was related to a higher VO2max, but not to time spent on physical activity. This suggests that in this age group intensity must be high enough to have an effect on VO2max before a preventive effect is present.

Validity of individual portion size estimates in a food frequency questionnaire

BACKGROUND

Dietary surveys often rely upon subjects' ability to estimate their portion sizes instead of weighing them, but information on the validity of such estimates is lacking. This study investigated the validity of estimated portion sizes from a self-administered food frequency questionnaire including photos.

METHODS

Validity was evaluated by comparison with portion sizes from 14-day weighed food records. Eight sets of photos were included in the study (three meat dishes, one fish dish, three vegetables, potatoes), each set with four options. Subjects (59 men, 85 women) were 40-64 years.

RESULTS

The majority of subjects (85-95%) selected the most correct photo or a neighbouring photo. However, regression analyses showed that the relationship between the estimated and the measured portion sizes was relatively weak for most of the foods tested, and correlations were only significant for three of the eight foods. This apparent contradiction was partly due to the pattern of the error: subjects selecting small portions had underestimated their actual portions while subjects selecting large portions had overestimated them. This error pattern could not be explained by the theoretical error resulting from the use of four discrete portion sizes instead of continuous weights, neither was it a simple consequence of the unidirectional errors at the extreme ends. Actual portion sizes varied from day to day, with intra-individual coefficients of variation of 34-40%.

CONCLUSIONS

The photos used in the present study were of limited value for ranking individuals correctly according to their actual portion sizes. Whether this is a common feature of photos used in food frequency questionnaires remains to be answered.

Changes in CHD risk factors with age: a comparison of Danish adolescents and adults

In 1983 a representative sample of Danish adolescents 16-19 yr of age were selected to participate in a study to determine risk profile for coronary heart disease. Eight years later (1991), we performed a follow-up study of the same participants 23-27 yr of age to compare risk factors. In the young adults power was generally high, 48.0 (SD +/- 7.8) and 39.6 (SD +/- 6.5) ml.min-1.kg-1 for men and women, respectively. Only 30% of the men and 26% of the women did not regularly participate in sport activities. Seventy-five percent of both genders bicycled daily, 50% of the men and 42% of the women as their daily transportation year round. Twenty percent, more men than women, were considered to be inactive. Women had a higher ratio of HDL-C/C than men (0.32 for women vs 0.26 for men). Mean values for blood pressure were 134/83 mm Hg and 122/78 mm Hg for men and women, respectively. Thirty-eight percent of the men and 10% of the women had an elevation above 140/90 mm Hg in either systolic blood pressure (SBP) or diastolic blood pressure (DBP). Cholesterol levels were high (10%) when compared with the U.S. population, but triglyceride levels were substantially lower (40%). Comparing the 1991 adults with the 1983 adolescents, the ranges were wider. In conclusion, the risk factor profile changes in men were less favorable than the profile for women; the changes in high risk groups were larger than changes in mean values.

Dietary factors related to fitness in young men and women

BACKGROUND

In a previous paper we reported an inverse relationship between fitness and serum lipids in this group of young subjects. The present study investigates whether a higher fitness level was associated with a more prudent diet and whether this contributed to the observed relationship between fitness and serum lipids.

METHODS

The study sample, comprising 70 women and 49 men ages 23-27 years, was a subgroup of a large random sample. Aerobic fitness was measured directly as maximal oxygen uptake (ml O2 min-1 kg-1) and dietary intake as 7-day food records.

RESULTS

The highest fitness tertile had an intake of dietary fiber higher than that of the lowest tertile (25.2 g/10 MJ vs 21.9 g/10 MJ, P < 0.05) and a lower intake of sucrose (7.2 E% vs 9.8 E%, P < 0.01), whereas total fat intake and the ratio between polyunsaturated and saturated fatty acids were similar (35.4 E% vs 36.5 E%, P > 0.05, 0.39 vs 0.34, P > 0.05, respectively). No differences were observed in intake of alcohol, protein, and total carbohydrate. Multiple regression analyses showed no impact of dietary variables upon the relationship between serum lipids and fitness.

CONCLUSIONS

Better fitness was associated with a better dietary composition with respect to dietary fiber and sucrose, but not to fat. The observed inverse relationship between fitness and serum lipids was not related to diet.

Detection of underestimated energy intake in young adults

BACKGROUND

Critical evaluation of energy intake data from dietary studies is difficult but important. A simple approach has been suggested using minimum cutoff limits for the ratio of energy intake to basal metabolic rate as predicted from body weight (EI/BMR(est.)). This study investigates the potential of this particular approach in young subjects.

METHODS

Energy intake during strictly controlled dietary intervention studies (2-6 weeks or 8 months) was compared with reported intake before the study started (7 days' weighed food records). Participants were 48 men and 22 women, 20-30 years.

RESULTS

Mean EI/BMR(est.) values during the intervention study were 1.92 for men and 1.77 for women. Reported intakes before the study were only slightly lower (women 8%, P < 0.05, men 5%, P > 0.05). Two EI/BMR(est.) limits were tested. Smaller underestimations could be detected by applying calculated cutoff limits based on average EI/BMR(est.) values from the intervention studies instead of published limits assuming a low physical activity level (6% versus 22% underestimation of group intake).

CONCLUSIONS

These results suggest that for the evaluation of energy intake of young adults it is more meaningful to use EI/BMR(est.) cutoff limits which assume a moderate, instead of a low, average physical activity level.

Cholesterol-lowering diets may increase the food costs for Danish children. A cross-sectional study of food costs for Danish children with and without familial hypercholesterolaemia

Food costs for 30 children under dietary treatment for familial hypercholesterolaemia were compared with those of 105 other Danish children. The daily intake of macronutrients and the daily cost of the diet for each child were calculated from dietary intakes and average prices of 365 different food items. The mean +/- SE percentages of energy (E%) from fat in the diet of children with and without known familial hypercholesterolaemia were 23.6 +/- 0.8 E+ and 34.5 +/- 0.5 E%, respectively (P < 0.001). The dietary costs per MJ in these two groups were 3.79 +/- 0.12 Danish crowns (DKr) and 3.34 +/- 0.05 DKr (P < 0.001), taking into account food wastage due to preparation and cooking. The cost per unit of energy increased with decreasing fat energy percentage of the diet for all children as one group (r = -0.37, P < 0.001), as well as for the group of children without familial hypercholesterolaemia (r = -0.35, P < 0.001). Stepwise multiple regression analysis showed that the differences in cost per MJ between the groups could be explained primarily by differences in percentage of energy from fat. We conclude that a reduction of dietary fat from 35 E% to 25 E% may increase food costs by 10-20% for Danish children.

Maximal oxygen uptake, maximal voluntary isometric contraction and physical activity in young Danish adults

In a randomly selected sample of 88 men and 115 women, aged 23-27 years from Denmark, maximal oxygen uptake (VO2max), maximal voluntary isometric contraction (MVC) in four muscle groups and physical activity were studied. The VO2max was 48.0 ml.min-1.kg-1 and 39.6 ml.min-1.kg-1 for the men and the women, respectively. The MVC was 10% lower than in a comparable group of Danes of the same age and height studied 35 years ago. Only in men was sports activity directly related to VO2max (ml.min-1.kg-1; r = 0.31, P < 0.01). The MVC of the knee extensors was related to VO2max in the men (r = 0.31, P < 0.01), but there was no relationship between the other measurements of MVC and VO2max. In the women VO2max (ml.min-1.kg-1) was only related to body size, i.e. body mass index, percentage body fat and body mass [(r = -0.47, -0.48 (both P < 0.001) and -0.34 (P < 0.01), respectively)]. There were differences in VO2max in the men, according to education and occupation. Blue collar workers and subjects attending vocational or trade schools in 1983 had lower VO2max, and more of them were physically inactive. In the women differences were also found, but there was no clear pattern among the groups. More of the women participated regularly in sports activity, but more of the men were very active compared to the women.

Tracking of cardiovascular disease risk factors including maximal oxygen uptake and physical activity from late teenage to adulthood. An 8-year follow-up study

OBJECTIVES

The aim of the study was to analyse changes in coronary heart disease (CHD) risk factors from adolescence to young adulthood, and how changes in risk factors relate to changes in lifestyle.

DESIGN

A randomized sample of school children was tested in 1983 and followed-up 8 years later. In 1983 a dropout of 0.7% was found and the sample was representative of 16-19-year-old Danes.

SUBJECTS

Subjects followed-up 8 years later (two-thirds of the original sample) were 88 male and 115 female 15-19-year-old school children attending 18 high schools, nine vocational and nine trade schools, throughout Denmark.

MAIN OUTCOME MEASURES

Height, body weight, body fat, occupation and coronary heart disease risk factors including physical activity (PA), fitness, blood pressure (BP), serum cholesterol, HDL cholesterol, triglyceride (TG) and smoking habits were assessed.

RESULTS

In males all risk factors increased: the increases in total cholesterol level and systolic and diastolic BP were large, 0.85 mmol l-1 and 11 mmHg, respectively. In females, the risk for some factors increased (total cholesterol and BP), others decreased (higher HDL cholesterol), and triglyceride did not change. Significant tracking was found in both sexes, with the highest correlation coefficients in men. A total risk score was calculated by categorizing risk factors into six groups--1 to 6--and then adding the scores. Pearson correlation between the total risk scores in 1983 and 1991 in men was r = 0.67 (P < 0.001). Only a weak association was found for the total risk score in women. Nearly 50% of the boys, who were initially in the upper quintile of risk, were still in the upper quintile 8 years later for most risk factors. In men, the changes in risk factors were related to social factors. Blue-collar workers and the unemployed had the highest increase in risk factors, and the largest decrease in VO2max (ml min-1 kg-1) when analysed together. In both sexes the best relationship between 1983 and 1991 values was found in body mass index (BMI). Leisure time physical activity (PA) and triglyceride (TG) had a low correlation between 1983 and 1991 values. Physical activity had a non-significant correlation over time for women, indicating that PA in 1983 did not predict PA in 1991 at all.

CONCLUSION

Coronary heart disease risk factors tracked in both males and females, but only in males was a strong relationship found for total risk from adolescence to young adulthood, indicating the influence of a poor lifestyle in high-risk men. Lower social status related to higher risk.

Dietary guidelines and food recommendations in Denmark. Nordic Committee of Foods, Nordic Council of Ministers, National Research Council, Denmark

In Denmark the official dietary guidelines and food recommendations are expressed in the Five Dietary advices and the Danish food circle. Such guidelines are entirely different from recommendations on nutrient intakes, which are expressed in terms of exact values and established through a more formal procedure. Some of the most fundamental principles for food recommendations given to the public are that they are perceived as consistent and based on a firm consensus, and that their relevance and translation into practical action is obvious to the public. When the situation in Denmark is compared to these principles the main issue turns out to be neither lack of consistency in recommendations issued by government agencies and voluntary health organisations, nor is it lack of consensus among the experts about the fundamental messages of the guidelines. A more important problem is that the public does not distinguish between formal recommendations from authorized sources, and a variety of advices from other sources as well as non-formal comments from individual scientists. A cause of serious concern is the fact that the Danish public seems to lack a realistic picture of what the dietary guidelines imply in terms of foods. A number of contradictions is built into the process of communicating dietary recommendations effectively to the public. These can only be solved if the process is planned on a long-term basis.

A new simplified dietary history method for measuring intake of energy and macronutrients

In this dietary history method, which preserves the characteristic features of the full dietary history, the principle of simplification is to group several food items into common codes. This enables us to complete both an interview and all nutrient calculations within 35-45 min. In this study we investigated whether the method could replace a 4-day food record for assessing individual intakes of energy and macronutrients. Dietary data were collected from 75 individuals (57 males and 18 females). Protein intake was validated by comparison with 24 h urinary nitrogen excretion (33 subjects), and energy intake was compared to weight maintenance energy intake from a later controlled diet study (19 subjects). When average intakes according to the two methods were compared, dietary history intakes were slightly higher than food record results (0-13%) except for alcohol. Comparison with urinary nitrogen excretion and energy intake data indicate that this is due to an overestimation by the dietary history method, rather than an underestimation by the food record. For individuals most of the correlations between the two methods were in the range 0.5-0.7, but alcohol correlation was down to 0.2. About 75% (53-93%) of the individuals at the extremes of the intake distribution were classified similarly by both methods. Although the ability of the dietary history to predict the individual food record results was unreliable the two methods agreed better when classifying individuals relative to certain cut-off points (sensitivity and specificity values of 0.7-0.9, relative to the food records).(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of individually estimated portion size data on the validity of a semiquantitative food frequency questionnaire

Using data from a Danish dietary validity study, we evaluated the influence of including individually estimated portion size data on the validity of a semiquantitative food frequency questionnaire. A total of 144 subjects, aged 40-64 years were included. Correlation coefficients and classification of subjects into quintiles according to their intake of foods and nutrients were used to compare questionnaire data, with and without individually estimated portion size data, with data obtained by 2 x 7 days weighed diet records. For men, the mean correlation coefficient for food group comparisons was 0.47 when information about individually estimated portion sizes for food items that do not come in natural units was included in the analysis. Using a common average portion size reduced the mean correlation coefficient to 0.45. For women, similar changes were observed (0.36 to 0.35). For nutrients the mean values for the comparison changed from 0.51 to 0.49 and from 0.39 to 0.40 for men and women, respectively. For both men and women the classification into quintiles according to their intake of foods and nutrients showed only minor differences. We conclude that little extra information was gained by including individual portion size information for food items that do not come in natural units. This may reflect that portion sizes are of minor importance compared with frequencies or that the relevant individual portion sizes were not estimated correctly.

Validation of a semiquantitative food frequency questionnaire developed in Denmark

In 1989, a self-administered food frequency questionnaire, including 92 food items and 40 portion-size photographs, was validated against two times seven days of weighed diet records. A total of 144 subjects, aged 40-64 years, from the general population in Copenhagen were included. Correlations between mean calorie-adjusted intakes from the two-week diet records and the food-frequency questionnaire ranged from 0.27 for vitamin A to 0.71 for calcium. In general, higher correlation coefficients were observed for men than for women. On average, about 70% of subjects were classified in the same (+/- 1) quintile in the food frequency questionnaire and the diet records. Of those subjects belonging to the lowest quintile, estimated from the diet records, 42% fell in the same quintile and 68% into the lowest two quintiles in the food frequency questionnaire. Findings were similar for the upper tail of the distribution. Gross misclassification, observed in the highest and lowest quintile, was found for 4% and 7% of the subjects, respectively. It is concluded that this food frequency questionnaire is a useful instrument for categorizing individuals according to their intake of nutrients and energy.

Development of a semiquantitative food frequency questionnaire to assess food, energy and nutrient intake in Denmark

Foods to be included in a Danish self-administered semiquantitative food frequency questionnaire were identified from food tables developed, together with data collected, for the survey 'Dietary habits in Denmark, 1985'. The questionnaire was to be used in a prospective study on diet, cancer and health, and the aim was to rank individuals with regard to intake of 19 different nutrients considered of prime importance in human carcinogenesis. The questionnaire for the dietary survey included 247 foods and recipes. From stepwise multiple regression analyses with the intake of each of the 19 nutrients as the dependent variable and the intake of the 247 foods and recipes as independent variables, the foods in the models explaining 90% of the between-person variability were considered for the final questionnaire. All relevant analyses were performed for the study group as a whole, for men and women separately, and in each gender for subgroups of energy intake. Taken together, the models explaining 90% of the between-person variability identified a total of 74 foods or recipes, which were important predictors of the intake of one or more of the nutrients considered. A few foods were excluded and a few foods were added to the final questionnaire based on common biological background information, and on information on foods providing important amounts of given nutrients, but which failed to contribute to regression analyses. The 92 foods and recipes, which were included in the final questionnaire provided altogether 81% of the average total supply of the nutrients.(ABSTRACT TRUNCATED AT 250 WORDS)