Estimation of the consumption of cold tap water for microbiological risk assessment: an overview of studies and statistical analysis of data.

The volume of cold tap water consumed is an essential element in quantitative microbial risk assessment. This paper presents a review of tap water consumption studies. Study designs were evaluated and statistical distributions were fitted to water consumption data from The Netherlands, Great Britain, Germany and Australia. We conclude that the diary is to be preferred for collecting water consumption data. If a diary is not feasible, a 24 h recall would be the best alternative, preferably repeated at least once. From the studies evaluated, the mean daily consumption varies from 0.10 L to 1.55 L. No conclusions could be drawn regarding the effects of season, age and gender on tap water consumption. Physical activity, yearly income and perceived health status were reported to influence water consumption. Comparison of the different statistical probability distribution functions of the datasets demonstrated that the Poisson distribution performed better than the lognormal distribution as suggested by Roseberry and Burmaster. For quantitative microbiological risk assessment (QMRA) it is recommended to use country-specific consumption data and statistical distributions, if available. If no country specific data are available we recommend to use the Australian distribution data from the Melbourne diary study (Poisson, lambda=3.49 glasses/d) as a conservative estimate.

Validation and sensitivity analysis of probabilistic models of dietary exposure to micronutrients: an example based on vitamin B6.

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.

Socio-economic status, dietary intake and 10 y trends: the Dutch National Food Consumption Survey.

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.

Selection of methodology to assess food intake.

OBJECTIVE: The aim of the EFCOSUM project was to develop a method to estimate both acute and usual consumption levels in European countries and for the sake of comparison, a common basic method for dietary assessment was needed. The method should allow a reliable comparison of the intake of relevant dietary indicators among large population groups. DESIGN AND RESULTS: The selection of methodology was based on the available literature and the expertise of the participants. To guide the selection process, decision trees containing all relevant moments of choice, alternatives and criteria for the selection of a method for food consumption measurement were developed. Considering that insight into average food and nutrient intake and their distribution in well-defined groups of individuals was important, it was decided that for the monitoring of the selected dietary indicators food consumption data should be collected at an individual level. Different methods were reviewed (24 h recall, dietary record, food frequency questionnaire, dietary history method). CONCLUSIONS: Since the 24 h recall method is applicable in large European populations of different ethnicity, has a relatively low respondent and interviewer burden, is open-ended and is cost-effective, this method can be considered as the best method for EFCOSUM to get population mean intakes and distributions for subjects aged 10 y and over in different European countries. Usual intake should be estimated by statistical modelling techniques, using two non-consecutive 24 h recalls and a food list to assess the proportion non-users for infrequently consumed foods.

Nutrition and health among migrants in The Netherlands.

OBJECTIVE: this paper aims to give a broad overview of published data on nutrition and health among migrants in the Netherlands, as well as data on determinants of health. RESULTS AND CONCLUSIONS: Depending on the definition, 9 to 17% of the population belongs to the group 'migrants' and this proportion is expected to grow in the coming years. Roughly 2/3 of migrants are of the first generation and on average, they are younger than the Dutch population. Relatively few data concerning the health status of migrants are available. The diet of migrants showed both positive (macronutrients) and negative (micronutrients) differences with the general Dutch diet. The risk of overweight was high among both children and adult women, and the data suggest a higher risk for Turkish and Moroccan groups than for Dutch groups. The importance of health determinants, such as smoking, alcohol use and physical and social environment, was different for migrants than for the Dutch population; however, there were also differences between ethnic groups. The limited data on morbidity for migrants suggest higher risks than for the indigenous population. The same holds for mortality data, especially for the younger age groups. In general, the data that are available suggest that the health status of migrants was less favourable than that of the indigenous population. However, there were also differences between the various groups of migrants. The lower socio-economic position of migrant groups partly explained the differences in health status. Nevertheless, a study among Turkish people indicated that their health status was lower than that of Dutch people of comparable socioeconomic status.

Analytical approaches to food-based dietary guidelines in the European setting.

OBJECTIVE: To show the effects of statistical approaches of data analysis to be used in the development of Food-Based Dietary Guidelines (FBDG). SETTING: Databases from dietary surveys in 6 European countries. RESULTS: Quantile analysis based on iron intake among adult women resulted in differences among European countries regarding (macro) nutrient intake and consumption of food groups. However, in all countries women in the highest quartile had a higher intake of energy and dietary fibre and a higher intake of most food groups. In developing FBDG adjustment of energy intake is recommended. Discriminant analyses showed that among Dutch women potatoes, red meat, sausages, offal, savoury snacks, eggs and total vegetables were found to be the most predictive for differences in iron intake. Relatively high correlations were observed for iron and dietary fibre and iron and (some) B-vitamins. Examples from cluster and factor analysis showed that this type of analysis considers the complexity of the dietary pattern and could also be a helpful instrument in the development of FBDG. CONCLUSIONS: The use of a nutrient distribution can be used as a minimum approach in developing FBDG. More advanced methods can also be used in addition to set priorities for FBDG and to analyse complete dietary patterns.

Eating patterns--temporal distribution, converging and diverging foods, meals eaten inside and outside of the home--implications for developing FBDG.

OBJECTIVE: A consideration of eating patterns in the general population is necessary when deriving food-based dietary guidelines (FBDG) as promoting the intake of one food may indirectly result in the increased consumption of another, which may not always be desirable. A number of issues that influence meal patterns such as temporal distribution of food intake (using data from the Netherlands), converging and diverging foods (using data from Ireland) and meals eaten inside and outside of the home (using data from the UK) are examined and discussed in the context of developing FBDG. SETTING: Food intake databases from three EU countries: The Netherlands, Ireland and the UK. RESULTS: The hot meal (dinner) was found to be the main contributor to the intake of energy and macro-nutrients in the Dutch population. It was also the main contributor to the intake of all micro-nutrients with the exception of calcium where the bread meal contributed a similar proportion as the hot meal to the intake of this micronutrient. Furthermore, fruit intake showed a very different temporal distribution to vegetable intake. Exploring the convergence of certain foods in the Irish population also revealed differences between fruit and vegetables. A low correlation was shown for consumers of fruit and vegetables indicating that being a high fruit consumer did not suggest being also a high vegetable consumer. An examination of where meals were consumed among British adults showed that 71% of all meals were consumed inside the home while 29% were consumed outside. 27% of food energy and 45% of alcohol energy was consumed out of home by the total population. In addition, those eating less of their foods out of home obtained a lower proportion of their food energy from fat and protein and a higher proportion from carbohydrate. A different demographic profile was associated with eating out compared to eating in, comprising more males and younger individuals. CONCLUSIONS: Information on patterns of food intake and food habits, specifically temporal distribution, the convergence and divergence of foods and foods consumed inside and outside of the home, give a culturally specific picture of food consumption practices within a population. This should enable the development of more culturally acceptable and realistic FBDG.

Assessment of dietary intake among Moroccan women and Surinam men.

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.

Impact of Mediterranean diet education versus posted leaflet on dietary habits and serum cholesterol in a high risk population for cardiovascular disease.

OBJECTIVE: To investigate the impact of intensive group education on the Mediterranean diet on dietary intake and serum total cholesterol after 16 and 52 weeks, compared to a posted leaflet with the Dutch nutritional guidelines, in the context of primary prevention of cardiovascular disease (CVD). DESIGN: Controlled comparison study of an intervention group given intensive group education about the Mediterranean diet and a control group of hypercholesterolaemic persons given usual care by general practitioners (GPs). SETTING: A socioeconomically deprived area in the Netherlands with an elevated coronary heart disease (CHD) mortality ratio. SUBJECTS: Two hundred and sixty-six hypercholesterolaemic persons with at least two other CVD risk factors. RESULTS: After 52 weeks, the intervention group decreased total and saturated fat intake more than the control group (net differences were 1.8 en% (95%CI 0.2-3.4) and 1.1 en% (95%CI 0. 4-1.9), respectively). According to the Mediterranean diet guidelines the intake of fish, fruit, poultry and bread increased in the intervention group, more than in the control group. Within the intervention group, intake of fish (+100%), poultry (+28%) and bread (+6%) was significantly increased after 1 year (P < 0.05). The intensive programme on dietary education did not significantly lower serum cholesterol level more (-3%) than the posted leaflet (-2%) (net difference 0.06 mmol l-1, 95%CI -0.10 to 0.22). Initially, the body mass index (BMI) decreased more in the intervention group, but after 1 year the intervention and control group gained weight equally (+1%). CONCLUSIONS: Despite beneficial changes in dietary habits in the intervention group compared with the control group, after 1 year BMI increased and total fat and saturated fat intake were still too high.

Dependence of dietary intake estimates on the time frame of assessment.

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.

Intake of fatty acids in western Europe with emphasis on trans fatty acids: the TRANSFAIR Study.

OBJECTIVE: To assess the intake of trans fatty acids (TFA) and other fatty acids in 14 Western European countries. DESIGN AND SUBJECTS: A maximum of 100 foods per country were sampled and centrally analysed. Each country calculated the intake of individual trans and other fatty acids, clusters of fatty acids and total fat in adults and/or the total population using the best available national food consumption data set. RESULTS: A wide variation was observed in the intake of total fat and (clusters) of fatty acids in absolute amounts. The variation in proportion of energy derived from total fat and from clusters of fatty acids was less. Only in Finland, Italy, Norway and Portugal total fat did provide on average less than 35% of energy intake. Saturated fatty acids (SFA) provided on average between 10% and 19% of total energy intake, with the lowest contribution in most Mediterranean countries. TFA intake ranged from 0.5% (Greece, Italy) to 2.1% (Iceland) of energy intake among men and from 0.8% (Greece) to 1.9% among women (Iceland) (1.2-6.7 g/d and 1.7-4.1 g/d, respectively). The TFA intake was lowest in Mediterranean countries (0.5-0.8 en%) but was also below 1% of energy in Finland and Germany. Moderate intakes were seen in Belgium, The Netherlands, Norway and UK and highest intake in Iceland. Trans isomers of C18:1 were the most TFA in the diet. Monounsaturated fatty acids contributed 9-12% of mean daily energy intake (except for Greece, nearly 18%) and polyunsaturated fatty acids 3-7%. CONCLUSION: The current intake of TFA in most Western European countries does not appear to be a reason for major concern. In several countries a considerable proportion of energy was derived from SFA. It would therefore be prudent to reduce intake of all cholesterol-raising fatty acids, TFA included.

Patterns of food and nutrient intakes of Dutch adults according to intakes of total fat, saturated fatty acids, dietary fibre, and of fruit and vegetables.

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.

Food-based dietary guidelines: some assumptions tested for The Netherlands.

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.

The contribution of various foods to intake of vitamin A and carotenoids in The Netherlands.

This study presents data on dietary intake of specific carotenoids in the Netherlands, based on a recently developed food composition database for carotenoids. Regularly eaten vegetables, the main dietary source of carotenoids, were sampled comprehensively and analysed with modern analytic methods. The database was complemented with data from recent literature and information from food manufacturers. In addition, data on intake of vitamin A are presented, which are based on the most recent update of the Dutch Food Composition Table. Intake of vitamin A was calculated for adult participants of the second Dutch National Food Consumption Survey in 1992, whereas intake of carotenoids was calculated for participants of the Dutch Cohort Study on diet and cancer, aged 55 to 69 in 1986. Mean intake of vitamin A amounted to 1.1 and 0.9 mg RE/day for men and women, respectively; the contributions of meat, fats and oils, vegetables and dairy products to total intake were 35%, 24%, 16%, and 16%, respectively. Mean intake of alpha-carotene, beta-carotene and lutein plus zeaxanthin was 0.7, 3.0, and 2.5 mg/day respectively for both men and women, while mean intake of lycopene was 1.0 mg/day for men and 1.3 mg/day for women. The most important foods contributing to intake of beta-carotene and lutein plus zeaxanthin were carrots (beta-carotene only), spinach, endive and kale.

Iodine intake and urinary excretion among adults in the Netherlands.

OBJECTIVE: To assess the prevalence of low and marginal iodine intake and urinary iodine excretion among adults in the Netherlands and to investigate determinants of urinary iodine excretion. DESIGN AND SUBJECTS: The study population consisted of 444 people aged 20-79 y, balanced for sex and 10 y age classes with an over-representation of people with a low habitual intake of vitamin B6. Food consumption was measured by three day food records and 24 h urine was sampled twice. RESULTS AND CONCLUSIONS: On average, iodine intake (mean of three days) in men was in the recommended range of 150-300 microg/d, but average intake in women was not. Mean 24 h urinary excretion values confirmed this observation. Estimation of the prevalence of low iodine excretion depended on the parameter chosen (absolute per 24 h, per kg body weight per 24 h, as concentration or per creatinin). The prevalence of low iodine supply, based on intake <100 microg/d (mean of three days) and intake or excretion parameters per creatinin excretion or per kg body weight, varied from 4-14% among adult women and from 5-17% among adult men. The prevalence of marginal iodine intake (<50 microg/d) and excretion was less than 5% in all adult age-sex groups. Urinary iodine excretion was most strongly associated with intake of iodine as such or as bread in combination with urinary excretion of sodium or potassium, confirming the importance of iodized salt (in bread) for iodine status. Age and total energy intake had a relatively minor impact on urinary iodine excretion.

Adequacy of the iodine supply in The Netherlands.

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.

Evaluation of the effect of the use of vitamin supplements on vitamin A intake among (potentially) pregnant women in relation to the consumption of liver and liver products.

OBJECTIVE: To assess the distribution of dietary vitamin A intake among Dutch women aged 16-50 and among pregnant women, and to evaluate the effect of the use of a vitamin A (1200 RE) containing multivitamin supplement in terms of nutritional and teratogenic risk. STUDY DESIGN: Data from the 2nd Dutch national food consumption survey (1992) were used for calculation of the vitamin A intake among 1725 16-50 year old women and 58 pregnant women. Calculations were performed with and without simulation of the use of a supplement containing 1200 RE vitamin A. RESULTS: Average vitamin A intake, based on a two-day dietary record method, compared quite well with recommended intake levels: 850 RE for the 16-50 year old non-pregnant (NP) women (RDA: 800 RE), and 990 RE for the pregnant (P) women (RDA: 1000 RE), respectively. The use of liver on one of the days under survey resulted in high intakes: 60% of the women in this subgroup exceeded the 'safe upper intake limit' of 3000 RE, while in 23% of the cases intakes were > 7500 RE. Those not consuming liver or liver products on the days under survey had relatively low average intakes [NP (n = 1472): 540 RE; P (n = 46): 720 RE]; about 70% of the non-liver users had intakes below the RDA. Including the daily use of a vitamin A containing multivitamin supplement with 1200 RE resulted in intakes > RDA, while only in 2% (NP), respectively 3% (P) of the cases the 'total' intake exceeded the 3000 RE level, but remained in all cases below 7500 RE/day. serving per day. CONCLUSION: The use of a vitamin A containing (maximum 1200 RE) multivitamin supplement can contribute to a controlled and adequate vitamin A intake and be considered as safe for pregnant women or women who wish to become pregnant, if the consumption of liver is completely avoided and the consumption of liver products is limited to maximum one.

[Regular vitamin A supplements are safe for pregnant women who consume few liver products]. / Reguliere vitamine A-supplementen veilig voor zwangeren die spaarzaam leverproducten gebruiken.

OBJECTIVE: To determine how much vitamin A is consumed through liver and liver products by non-pregnant and pregnant women aged 16-50 years, and to determine the implications for the use of multivitamin products. DESIGN: Secondary analysis on data from representative database Dutch National Food Consumption Survey. METHOD: Data were obtained from a Dutch National Food Consumption Survey (1992, method published earlier) regarding 1725 non-pregnant and 58 pregnant women aged 16-50 years who did or did not consume liver and (or) liver products. RESULTS: Average daily vitamin A intake (two consecutive days), was 850 retinol equivalents (RE) for non-pregnant and 990 RE for pregnant women, respectively (recommended daily allowances are 800 RE and 1000 RE). Average intakes of those not eating liver or liver products were 540 RE and 720 RE per day. In about 70% and 50% of the women respectively the intake was below the minimal requirement of 600 RE per day. The use of a vitamin A supplement providing 1200 RE per day among the non-liver users would in none of the cases have resulted in intakes higher than the threshold level of 7500 RE for teratogenic risks. Occasionally in 2-3% of the women, not using liver or liver products, maximum intake would exceed 3000 RE per day (the upper safe limit of intake according to the Dutch Health Council/Nutrition Council Committee). However, women using liver or liver products would be at risk of having too high intakes, above the threshold level of 7500 RE, irrespective of the use of vitamin supplements. CONCLUSION: Regular vitamin A supplements may be safely used by pregnant women who consume little or no liver or liver products.

Calculated iodine intake before and after simulated iodization (Dutch Nutrition Surveillance System).

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.