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Presents a study which looks at dietary risk factors among adults in the Netherlands, relating to nutrition. Information on study design and selection bias; Further detailed information.

Presents a study relating to the assessment of severe iodine deficiency among adults in the Netherlands and urinary iodine excretion. Methodologies used in the study; Results of the study; Discussion on the study.

Looks at a study which focuses on the intake of iron, and the iron status of adults in the Netherlands. Methodologies used in the study; Results of the study; Discussion on the study; Other detailed information.

Details on a study which focuses on the assessment of the adequacy of folate intake and status in adults of the Netherlands, relating to nutrition. Methodologies used in the study; Results of the study; Discussion on the study.

Presents a study on the dietary, physical, biochemical and lifestyle determinants of vitamin B6 status parameters in adults. Information on methodologies used in the study; Results of the study; Discussion on the study; Other information.

Presents a study on the Dutch Nutrition Surveillance System, which is monitoring the micronutrient status of the adult Dutch population, with reference to vitamin B6. Detailed information on the methodologies used in the study; Discussion on the study; Further detailed information on the study.

Focuses on the study of the dietary intake, with reference to that of vitamin B6. Methodologies used in the study; Results of the study; Discussion on the study; Indepth look at the study.

Presents a study which investigates the nutritional status of the Dutch adult population. Methodologies used in the study; Results of the study; Discussion on the study; Indepth look at the study.

Probabilistic modelling can be used to get an insight into the variability and uncertainty of the nutrient intake in a population. When a probabilistic model is used, it is important that it is validated. Furthermore, a sensitivity analysis of the model output can give an insight into the most important input variables of the model and can be used as an aid to describe the reliability of the model. In this study, four models to estimate vitamin B(6) intake among males and females were validated using the method of Kaaks et al. This method compares the relationship between three different kind of measurements with the unknown 'true' intake. In each of these four models, only one input variable (concentration or bioavailability) was changed compared with a reference model. A sensitivity analysis was also performed. The results of the validation showed that for males, a model using a fixed bioavailability factor at the food group level was valid, while for females a model using either a fixed value or a distribution for the bioavailability factor was valid. Use of a distribution for the concentration of vitamin B(6) in supplements was not valid. The results of the sensitivity analysis showed that the concentration of vitamin B(6) in food and supplements was the key contributor to variability and uncertainty in the model estimates of vitamin B(6) intake, in both males and females. All results indicated that when taking variability and uncertainty into account by using probabilistic modelling, the effect on the nutrient intake for nutrients that are present in many common eaten foods, is small. For these broadly available nutrients, fixed concentrations and bioavailability factors give a good estimate of the nutrient intake in a population. When using probabilistic modelling, it is very important to collect more actual information about the concentration.

Objective: To study differences in dietary intake between adults with different socioeconomic status (SES) and trends over time., Design: Cross-sectional study based on data of three Dutch National Food Consumption Surveys (DNFCS-1 1987/88; DNFCS-2 1992; DNFCS-3 1997/98), obtained from a panel by a stratified probability sample of the non-institutionalized Dutch population., Subjects: A total of 6008 men and 6957 women aged 19 y and over., Methods: Dietary intake was assessed with a 2 day dietary record. Background information was obtained by structured questionnaire. Sociodemographic variables were available from panel information. SES, based on educational level, occupation and occupational position was categorized into (very) low, middle and high. Analysis of variance with age as covariable was used to explore the effects of SES on dietary intake and anthropometry. Statistical tests for trend were carried out with models in which week-weekend-day effects and an interaction term of time with SES were also included., Results: The prevalence of obesity and skipping of breakfast was higher among people with a low SES. In all three surveys, subjects in the (very) low SES group reported having a higher consumption of potatoes, meat and meat products, visible fats, coffee and soft drinks (men only). Subjects with a high SES reported consuming more vegetables, cheese and alcohol. As regards nutrients, in all surveys a higher SES was associated with higher intake of vegetable protein, dietary fibre and most micronutrients. A higher SES was also associated with a lower fat intake but the differences between social classes were rather small and not consistent when the contribution of alcohol to energy intake was taken into account., Conclusion: In general, dietary intake among subjects in higher SES groups tended to be closer to the recommendations of the Netherlands Food and Nutrition Council and this phenomenon was quite stable over a period of 10 y.

Objective: To establish a method for food consumption data collection in ethnic groups in the Netherlands., Methods: Two pilot studies have been carried out, one among Moroccan women and one among Surinam men. First, focus group discussions were held to obtain background information from members of the target population. For food consumption assessment 2 X 24-h recall was chosen. Furthermore, background information on age, place of birth, frequency of visits to Morocco or Surinam, Dutch language skills, meal pattern, food purchases and antropometric measurements were taken., Results: It was found that the diets of both Moroccan women and Surinam men tended to approach the recommended daily intake of macronutrients more than the average intake of a Dutch person. However, reported energy and micronutrient intake on the second day of the dietary recall was lower than on the first recall day., Conclusion: The 24-h recall is a suitable method for food consumption measurements among Moroccan and Surinam people. On the other hand, the interviewer must be aware of potential under-reporting, especially during the second recall.

Food chemical risk management needs, among other things, assessment of exposure. For dietary intake food consumption surveys are the data source to be used. One complicating factor in the usage of these data is the dependence of dietary intake estimates on the time frame of assessment. Central to this time dependence is the within-subject variation regarding the usage of food products and, as a consequence, the intake of chemicals. Within-subject variation is mostly as large as or larger than between-subject variation. Expressed per kilogram body weight, average (total) variation in intake variables depends on the age group, with variation usually being greater at younger age, most likely as a result of the higher intake levels at that age. Combination of age groups results in an increase in between-subject variation, and correction based on the figures for the total population will be too small. Ideally, exposure data for all days of one's life should be available to assess lifetime exposure. Since information on all these days is not an attainable and practical option, and not an option to strive for either, the most recent available data should be used that can be extended with simulation studies to anticipate future developments. The present food consumption surveys available in European countries are based on data that vary from 1 day (24-h recall and dietary record) to habitual intake (dietary history and food frequency). The data of a survey based on 1 day refer to 0.004% of an average lifetime of 70 years. Based on the demographic picture of the population, a reasonable approximation of lifetime intake can be obtained. The proportion of users and the consumption level among users depend on the time frame of assessment, especially for irregularly consumed products. Usage of the concept of "users only" overestimates lifetime exposure of the population, the extent of overestimation depending on the duration of the survey. The likelihood that all consumers have been exposed to a chemical once during a lifetime period is realistic in the sense of the best approximation of reality. As a result of this assumption all exposure assessments will have a similar point of departure and the dependence of the results on the food consumption method will be reduced.

Recently, the concept of food-based dietary guidelines has been introduced by WHO and FAO. For this concept, several assumptions were necessary. The validity and potential consequences of some of these assumptions are discussed in this paper on the basis of the Dutch National Food Consumption Surveys. The topics were interrelationships among dietary characteristics, nutrient density, diets in accordance with the guidelines, and food variety. To obtain insight into overall diet quality, a dietary quality index based on nutrients and a food-based quality index based on food groups were created and tested. As expected the results showed that a higher dietary quality index was associated with an improved intake of the nutrients included in the index, in particular a lower intake of total fat and cholesterol. This was related to a lower consumption of cheese, fats and oils, meat and meat products, and a higher consumption of fruit and vegetables. The information obtained with a dietary quality index can be used to assess the feasibility of a particular goal in combination with other relevant goals and to obtain clues or confirmation for recommendations regarding food consumption. The food-based quality index created showed that a combination of several food-based goals (formulated in quantitative terms) was associated with an increase in food consumption, without a clear relevance for the dietary quality. Therefore, the formulation of food-based guidelines should be based on explicitly stated dietary goals. The findings regarding nutrient density were in the direction of what was assumed, namely a positive association between density and absolute intake, although the expected effects were not completely found. The results regarding the association between variety and dietary intake were characterized mainly by differences in quantity rather than dietary quality. The data indicate that energy intake may be an important pitfall in implementing food-based dietary guidelines, that 'eat a variety of food' can be an empty slogan and that nutrient density is positively related to the absolute intake of specific micronutrients. Further, the 'absence' of interrelationships among risk nutrients indicates that a selection process has to be applied.

Dietary intake characteristics were studied among 3833 adults of the second Dutch National Food Consumption Survey held in 1992. The subjects were classified into three groups based on their intake of total fat (% energy), saturated fatty acids (% energy), dietary fibre (g/MJ), and fruit and vegetables (g/d). All the classifications resulted in differences in energy intake. Except for dietary fibre, the mean energy intake was higher in the higher-intake tertiles. For the classification based on total fat, saturated fatty acids and dietary fibre the more prudent diets were accompanied with a lower energy-intake. As to the consumption of food groups, differences existed in both the proportion of consumers and in the mean consumption among users. It is concluded that the trends observed are probably more important than the actual figures.

Objective: To assess the adequacy of the iodine supply in the Netherlands and to study possible ways of increasing the iodine intake. DESIGN, SETTINGS AND SUBJECTS: Goitre and nutrition surveillance studies (intake and urinary excretion of iodine) among population groups (age: 12-85 y, n=57-1704) in the Netherlands in the period 1981-1993. Simulation studies, based on the Dutch Nutrition Food Consumption Surveys (n=6000), calculating iodine intake among population groups after fictively iodizing different food groups., Results: Mean intake of iodine, measured with different food consumption methods in the period 1984-1993, met the recommended amount of 150-300 microg per day in males, but not in females. Median urinary iodine excretion levels were in the range for mild Iodine Deficiency Disorders in both sexes. According to dietary methods reflecting habitual intake and urinary iodine excretion per kg body weight or per mmol creatinin the prevalence of low iodine supply among adults is between 4 and 20% for women and between 5 and 15% for men. Iodization of different products would increase mean iodine intakes by up to 45% and would give a reduction of roughly 65% in the prevalence of low iodine intakes., Conclusion: The present goitre prophylaxis in the Netherlands is not optimally effective. The iodine supply is below cut-off points in 4-20% of the adult population. It is possible to decrease the prevalence of low iodine intakes without a clear risk of exceeding the maximum acceptable daily iodine intake by increasing the iodine content of baker's salt and/or by adding iodine to other foods.

Objective: The correct classification of adults with a habitual low vitamin B6 intake by means of a food frequency questionnaire (FFQ). Assessment of reproducibility of the food frequency questionnaire and of the relative validity as compared to 3 d diet records (DR)., Design: A self-administered food frequency questionnaire (FFQ) to measure habitual vitamin B6 intake was developed using the data base of the first Dutch National Food Consumption Survey 1987/88 (DNFCS). The frequency and quantity of consumption of 92 (combinations of) food products, contributing to about 95% of vitamin B6 intake, were asked for. Recent food consumption was measured with 3 d diet records. Reproducibility of the FFQ was assessed after 10 months (n = 330)., Subjects: Randomly selected men and women aged 20-79 y, stratified for 10 y age classes and sex., Results: A total number of 2867 FFQs was adequately completed (response rate 46%). A low vitamin B6 group was selected from the lowest tertile of age-gender specific vitamin B6 intake (36 men and 36 women, aged 20-49 and 36 men and 36 women, aged 50-79) and a so-called reference group (n = 300) was selected at random. The ratio of vitamin B6 intake according to FFQ and DR (FFQ/DR) varied between 0.77 and 0.99 for the various age-gender-study groups; for vitamin B6/g protein the FFQ/DR ratio varied between 1.00 and 1.10. After correction for intraindividual variance Pearson correlation coefficients between vitamin B6 intake according to FFQ and DR varied between 0.27 and 0.95 for the various age-gender-study groups, for vitamin B6/g protein the corrected Pearson correlation coefficients varied between 0.27 and 0.65. Of the subjects selected in the low B6 groups, 61-81% fell in the lowest tertile of vitamin B6 intake according to diet records and 3-6% fell in the extreme opposite tertile. The percentage subjects selected in the same/opposite quartile of vitamin B6 intake according to FFQ and DR was 50/11 for men, and 45/18 for women. Pearson correlation coefficients for vitamin B6 intake according to the first and the second FFQ were 0.64 and 0.72 for men and women, respectively; for vitamin B6/g protein these values were 0.70 and 0.51 for men and women, respectively. The proportion of subjects classified in the same/extreme opposite tertile of vitamin B6 intake was 56/6 and 62/5 for men and women, respectively., Conclusions: It is concluded that the FFQ was adequate for the selection of subjects with a habitually low vitamin B6 intake.

Objective: To describe the rationale, design and methods for a nutrition surveillance study with special reference to vitamin B6 and other micronutrients., Rationale and Design: Several studies in the Netherlands have shown that differences in dietary intake and in nutritional status indicators are relatively small among various socio-demographic groups, so that the relevance of this traditional risk group identification in terms of public health and nutrition policy is limited. Therefore, it was decided to use the diet itself as primary selection criterion for a study on the adequacy of the vitamin B6 supply. The first Dutch national food consumption survey in 1987/88 showed, among other things, that mean vitamin B6 intake (per gram of protein) was substantially below the adequate level for all age-gender groups studied. Since the potential impact on public health of this observation may be relatively large, intake of vitamin B6 was chosen as first selection criterion. A study design that creates the largest possible distinction in vitamin B6 intake would be most efficient to study the health risks as a consequence of a low vitamin B6 intake. Several arguments, such as the need to estimate the prevalence of an inadequate status of vitamin B6 and other micronutrients, led to the decision to use a random population sample as a reference group for comparison with the group with low habitual vitamin B6 intake. Other major arguments underlying the study design and the selection of the nutritional status indicators, as well as the framework of the Dutch Nutrition Surveillance System, are discussed. Finally, the design and methods of the study are described in detail (except food consumption methods).

To assess the level of exposure to food contaminants (cadmium, lead, PCBs, DDT, hexachlorobenzene, nitrate and malathion) a total-diet study was carried out. A total of 226 food products were analysed individually; the concentration of contaminants in products not selected for analysis was estimated with the help of published data. The results of the analyses and estimations were used as input for the first Dutch National Food Consumption Survey (1987-1988) (n = 5898, age 1-85). Mean intakes of all contaminants analysed did not exceed the acceptable daily intake (ADI) or comparable values in any of the age-sex groups. Comparison of the results with those of previous total diet studies suggests that the intake of all contaminants analysed had declined between 1976-1978 and 1988-1989. In younger age groups an intake of lead and cadmium exceeding the tolerable daily intake (derived from the WHO/FAO provisional tolerable weekly intake) was found in 1.5% of individuals at most. For the older population groups and for the other contaminants in all population groups mean and maximum intakes were substantially below the ADL. However, individual intakes above the ADI for nitrate were found in 3-23% of individuals. For chronic exposure these percentages are likely to be overestimated because of the short time frame for food consumption measurement. In general, the difference between mean intake and tolerable daily intake was smallest for children aged 1-4. Therefore, it is recommended that future research is concentrated on the intake of contaminants in younger age groups.

To estimate the effect of possible goitre prophylactic measures on the intake of iodine among population groups, simulation studies, based on the first Dutch National Food Consumption Survey, were carried out. Iodine intake figures and prevalence of low intakes were calculated after fictively iodizing either bread, a combination of industrial products, milk and dairy products (without cheese) or margarine and shortenings. In addition, the effect of iodizing both bread and cheese or bread + biscuits + rusks was calculated. The simulated iodization of different products increased mean calculated iodine intakes by up to 45% and gave a reduction of 60-90% in the prevalence of iodine intakes below 100 micrograms/day. The maximum acceptable intake of 1 mg iodine per day was never reached by any subject (average of 2 days). It is concluded that it is possible to increase substantially the mean iodine intake of the Dutch population and to decrease the prevalence of low iodine intakes without a clear risk of exceeding the maximum acceptable daily oral iodine intake.

Vitamin B6 is considered to be a risk nutrient for elderly people. Conversion of most naturally available vitamin B6 to its functional coenzyme pyridoxal 5'-phosphate (PLP) depends on riboflavin. Therefore, interrelations were studied between riboflavin and vitamin B6 among 473 elderly people not using supplements containing B-vitamins. Habitual food consumption (assessed through dietary history with cross-check), plasma PLP levels and enzyme activities of erythrocyte glutathione reductase (EGR) and erythrocyte aspartate aminotransferase (EAST), with and without added flavin adenine dinucleotide and PLP, respectively, were determined. The results showed that unstimulated and stimulated EAST activity was higher when EGR activity (both simulated and unstimulated) was higher. Plasma PLP was positively associated with (un)stimulated EGR activities, but these correlations were not significant, probably due to the lower number of observations. Adjusted for the intake of vitamin B6 similar observations were made for the forementioned interactions between the biochemical indicators. To identify the strongest correlates of the vitamin B6 status indicators, stepwise regression analysis was carried out. The results showed that in each model an indicator of the riboflavin status was included. Our findings suggest an interaction between the status of riboflavin and vitamin B6 at intake levels normally found among Dutch elderly people.

In the course of four controlled experiments on the effect of specific dietary components on cardiovascular risk factors, the effects on blood pressure of various sources of dietary fiber, of type and amount of dietary fat, and of animal versus plant were measured in young normotensive volunteers. In each of the four experiments a group of 50 to 75 healthy student volunteers received a control diet for 11/2 to 21/2 wk. They were then randomized into subgroups which received various test diets for periods ranging from 4 to 12 wk. In each experimental one group received the control diet throughout the whole experimental period. Diets differed between groups in one dietary component only. All foodstuffs were weighed out individually according to each person's energy needs. Body weights and Na intake were controlled. Initial blood pressures were about 120 mm Hg systolic and 70 mm Hg diastolic. Both systolic and diastolic blood pressure decreased during the test period in all four experiments on almost every diet, including the control diets, by about 0 to 5 mm Hg. However, changes in blood pressure over the test period were never significantly different between the test groups and the control groups. Thus, none of the investigated dietary factors had a demonstrable effect on blood pressure in young normotensive persons.

The effect of different amounts and types of dietary fat on faecal steroid excretion in healthy volunteers was examined. In the first experiment with sixty volunteers four diets which differed in type and amount of dietary fat only were compared during a test-period of 5 weeks. Faeces were collected during 7 days before and at the end of the test period and analysed individually. In the second experiment with thirty-five volunteers, a low fat diet containing 22% of energy as total fat (4% as polyunsaturated fatty acids) was compared with a moderate fat diet (30% of energy as total fat; 11% as polyunsaturated fatty acids) during 13 weeks. Faeces were collected during the first 7 days of the test period and during 7 consecutive days near the end of the test period and pooled per dietary group. Excretion of faecal neutral steroids and bile acids was not significantly influenced by amounts of total fat ranging from 22% to 40% of daily energy or by differences in polyunsaturated to saturated fatty acids ratio from 0 . 2 to 1 . 7. The only exception was the excretion of bile acids in the second experiment which was 0 . 19 mmol/24 h (75 mg/24 h) higher on the low fat diet than on the moderate fat, high polyunsaturated fat diet (P less than 0 . 01).

We have studied whether a low-fat diet is as effective in lowering some risk factors for atherosclerosis as a diet rich in polyunsaturated fat (PUFA). During a 2.5 week control period, 60 volunteers were given a moderate-fat diet (MOD) providing 30% of the daily energy intake (energy %) in the form of fat, one-third of which was PUFA. For the next 5 weeks subjects were divided into 4 groups and received diets providing varying amounts of total fat and of PUFA: for group LO, 20 energy % PUFA; group HIPUF, 40 energy % fat and 19 energy % PUFA; and group HISAT, 40 energy % fat and 3 energy % PUFA. The diets contained the same amounts of cholesterol, phytosterols, oligosaccharides and other nutrients, known to affect serum lipid levels. All food was prepared daily and weighed out for each individual appropriate to his energy needs. Nutrient intakes were checked by 7-day records and by chemical analysis of double portions. On diet LO, total serum cholesterol concentration increased by 0.25 mmol/l while HDL cholesterol concentration did not change significantly. The HDL cholesterol/apoprotein-A1 ratio fell, and VLDL and LDL triglyceride centrations were elevated. On the HIPUF diet, total serum cholesterol concentration was not significantly lower, but HDL cholesterol concentration increased by 0.10 mmol/l. On the HISAT diet, total serum cholesterol concentration went up by 0.38 mmol/l; 0.12 mmol/l of this was due to HDL. LDL cholesterol/serum apoprotein-B ratios were unaffected by any of the diets. It was concluded that after 5 weeks, the influence of a low-fat, high-carbohydrate diet on the concentrations of serum lipoproteins was less favourable than that of moderate- or high-fat diets rich in polyunsaturated fatty acids.

Serum samples were collected from 7- and 8-year-old boys in 16 countries with different rates of coronary heart disease (CHD) mortality. Both serum total and high-density lipoprotein (HDL) cholesterols were lower in developing countries than in affluent countries. The mean of the HDL cholesterol/total cholesterol ratio varied within narrow limits: 0.24-0.27 in Asian countries, 0.30-0.36 in Africa, and 0.30-0.37 in the USA and Europe. Thus both total and HDL cholesterol increased under the influence of a more affluent diet. This conclusion is supported by results from controlled trials. Student volunteers received all their food from us for periods of 8 to 16 weeks. Diets were prepared from regular foodstuffs, in such a way that they differed in one nutrient only. Dietary composition was confirmed by double portion analysis. A moderate fat diet with a high P/S ratio was compared with a low-fat, low-PUFA diet and with two high-fat diets having a high or low P/S ratio. Both low-fat and high P/S diets effectively lowered total serum cholesterol. However, HDL was depressed by the low-fat diet in comparison with diets with a higher fat content, whether high or low in polyunsaturates. This difference in HDL persisted for at least 3 months. This suggests that "Western" diets, usually high in fat, elevate both total and HDL cholesterol concentrations in children and young adults.