Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Kenmerkende aspecten van agrarische kinderopvang : De aanwezigheid, het belang en de (mogelijke) effecten volgens experts, ouders en kinderen
Ypma, T. ; Jong, D. de; Schoutsen, M.A. ; Poelarends, J.J. ; Singer, Elly - \ 2015
Praktijkonderzoek Plant & Omgeving B.V. - 32 p.
kinderverzorgers - kinderverzorging - dagopvang voor kinderen - schoolkinderen - peuters en kleuters - vroege jeugdontwikkeling - recreatiecentra - vrijetijdsactiviteiten - kinderspelen - kinderboerderijdieren - landbouw - plattelandsomgeving - neveninkomsten - child careproviders - child care - child day care - school children - preschool children - early childhood development - leisure centres - leisure activities - children's games - children's farm animals - agriculture - rural environment - supplementary income
Agrarische kinderopvang is populair. Het aantal opvanglocaties groeit. Maar wat is dat nu eigenlijk, agrarische kinderopvang? Wat zijn de kenmerkende aspecten ervan? En wat voor mogelijke effecten hebben deze aspecten op kinderen? Ouders zien bijvoorbeeld dat kinderen contact maken met dieren. Maar wat betekent dat? Wat is het belang en effect ervan? Ook zien we op opvanglocaties dreumessen die steeds weer nieuwe dingen ontdekken en worden uitgedaagd tot bewegen. Wat is hier het belang en effect van? Literatuuronderzoek, observaties van onderzoekers, een ouderenquête, interviews met ouders en een project met BSO kinderen geven antwoorden op dit soort vragen. Ook andere aspecten zijn te vinden in deze brochure. Een uitgebreidere beschrijving van het onderzoek is te lezen in de achtergrondrapportage (
Overweight and obesity in primary-school children: a surveillance system for policy-making in Europe from 2007 onwards
Wijnhoven, T.M.A. - \ 2015
University. Promotor(en): Pieter van 't Veer, co-promotor(en): Joop van Raaij. - Wageningen - ISBN 9789462574656 - 265
overgewicht - obesitas - quetelet index - lichaamsgewicht - schoolkinderen - kinderen - kwantitatieve analyse - who - gezondheid van kinderen - risicoschatting - kindervoeding - lichamelijke activiteit - kleding - overweight - obesity - body mass index - body weight - school children - children - quantitative analysis - child health - risk assessment - child nutrition - physical activity - clothing

Trudy M.A. Wijnhoven

Overweight and obesity in primary-school children: a surveillance system for policy-making in Europe from 2007 onwards.


As a follow-up to the European Ministerial Conference on Counteracting Obesity convened in 2006 in Turkey, the European Childhood Obesity Surveillance Initiative (COSI) was launched by the Regional Office for Europe of the World Health Organization (WHO). COSI, a collaboration between WHO and interested Member States, aims to monitor the magnitude of overweight and obesity among primary-school children in European countries, to allow intercountry comparisons and to identify regional differences for informed policy-making. It collects at regular intervals data on weight and height of primary-school children and on their nutrition and physical activity behaviours, as well as on school environmental characteristics supportive to healthy nutrition and physical activity.


The research described in this PhD thesis is based on the data collected in the first two COSI rounds by 12 European countries in school year 2007/2008 and by 13 European countries in school year 2009/2010. Nationally representative samples of children aged 6–9 years were drawn, whereby a majority of the countries applied a two-stage school-based cluster sampling approach.

A total of 168 832 children in school year 2007/2008 and 224 920 children in school year 2009/2010 were included in the anthropometric intercountry data analyses. Children's weight and height were measured by trained examiners using standardized procedures. Participating countries were allowed to adhere to their local legal requirements by specified deviations from standardized procedures, such as in types of clothing worn by the children during weight and height measurements. For each country, the prevalence of overweight and obesity, as well as mean Z-scores of anthropometric indices of height, weight and body mass index (BMI) were computed.

The characteristics included in the analyses on the school environment referred to the frequency of physical education lessons, the availability of school playgrounds, the possibility to obtain food items and beverages on the school premises, and the organization of school initiatives to promote a healthy lifestyle. The school form was usually completed by the school principal or the teachers involved with the sampled classes. Data from 1831 schools in school year 2007/2008 and from 2045 schools in school year 2009/2010 were used. For each school, a school nutrition environment score (range: 0–1) was determined whereby higher scores correspond to higher support for a healthy school nutrition environment and the mean of the children's BMI-for-age Z-scores calculated.

Five countries in school year 2007/2008 provided children's data on 13 health-risk behaviours related to breakfast and food consumption frequency, physical activity, screen time and sleep duration (n = 15 643). These data were reported by the caregivers alone or jointly with their child. For each country, the prevalence of the risk behaviours was estimated, and associations between them and overweight and obesity examined by multilevel logistic regression analyses.


In both school years, a wide range in overweight and obesity prevalence estimates was found that differed significantly by country, as well as by European region. In all countries, the percentage of overweight children was about 20% or more (range: 18–57%), and the percentage of obese children was 5% or more (range: 5–31%). The findings suggest the presence of a north–south gradient with the highest overweight and obesity prevalence estimates found in southern European countries. Furthermore, changes in mean BMI-for-age Z-scores (range: from –0.21 to +0.14) and prevalence of overweight (range: from –9.0% to +6.2%) from school year 2007/2008 to school year 2009/2010 varied significantly among countries, whereas a period of two years is considered too short to identify these developments. The clothes-adjusted overweight prevalence estimates were lower by as much as 12% than the unadjusted estimates. Monthly BMI-for-age Z-score values within countries did not show systematic seasonal effects.

Large between-country differences were observed in both school years in the availability of food items or beverages on the school premises (e.g., fresh fruit could be obtained in 12–95% of schools) and in the organization of initiatives to promote a healthy lifestyle in the selected classes (range: 42–97%). The provision of physical education lessons and the availability of school playgrounds were more uniformly present across the countries (range: 76–100%). A large variation was also seen in school nutrition environment scores (range: 0.30–0.93) whereby countries with a low score (< 0.70) graded less than three out of five characteristics as supportive. High-score countries showed more often than low-score countries a combined absence of cold drinks containing sugar, sweet snacks and salted snacks on the school premises.

The prevalence of all 13 health-risk behaviours differed significantly across countries. For instance, the percentage of children who ate ‘foods like candy bars or chocolate’ > 3 days/week ranged from 2.2% to 63.4%; this figure ranged from 1.1% to 46.5% for those who ate ‘foods like potato chips (crisps), corn chips, popcorn or peanuts’ > 3 days/week. The range for children who did not have breakfast every day was between 4.4% and 32.5%, and from 4.8% to 35.0% for those who did not play outside ≥ 1 hour/day. Not having breakfast daily and spending screen time ≥ 2 hours/day were clearly positively associated with obesity. The same was true for eating ‘foods like pizza, French fries, hamburgers, sausages or meat pies’ > 3 days/week and playing outside < 1 hour/day. While a combination of multiple less favourable physical activity behaviours was clearly positively associated with obesity, a combination of the presence of multiple unhealthy eating behaviours did not lead to higher odds of obesity.


The results found in both COSI school years show that overweight and obesity among 6–9-year-old children are a serious public health concern, especially in southern European countries, and show the need for accelerated efforts to prevent excess body weight early in life by all participating countries. It was possible to detect relevant changes within a period of two years but to identify clear trends within countries, a longer time interval is necessary. The data on the school nutrition environment and the children's health-risk behaviours may assist policy-makers in monitoring their national policies targeting school settings and childhood obesity. In particular, promoting physical activity-related and discouraging sedentary behaviours among schoolchildren in the context of obesity preventive interventions seem to be essential.

Yellow cassava: efficacy of provitamin A rich cassava on improvement of vitamin A status in Kenyan schoolchildren
Talsma, E.F. - \ 2014
University. Promotor(en): Michael Zimmermann; Frans Kok, co-promotor(en): Inge Brouwer; Alida Melse-Boonstra. - Wageningen : Wageningen University - ISBN 9789461738554 - 143
cassave - provitaminen - retinol - vitamine a tekort - voedingstoestand - schoolkinderen - kenya - fortificatie - cassava - provitamins - vitamin a deficiency - nutritional state - school children - fortification

Background: Biofortified yellow cassava has great potential to alleviate vitamin A deficiency in sub-Saharan Africa and can be used as a complementary approach to other interventions. However, direct evidence whether yellow cassava can significantly contribute to the vitamin A intake and status of populations is required. The overall aim of this thesis is to provide proof of principle whether biofortified yellow cassava can improve the vitamin A status of schoolchildren in Kenya.

Methods: The research was conducted in Kibwezi district, Eastern Kenya. First the effect of daily consumption of yellow cassava was assessed in 342 primary school children in Kenya in a randomized controlled feeding trial with serum retinol concentration as primary outcome. Furthermore we investigated the sensory and cultural acceptability of yellow cassava in a cross-sectional study (n=140) in three primary schools for children as well as their caretakers. Next we studied the diagnostic performance of several proxy markers to assess vitamin A deficiency in comparison with serum retinol concentration as a field based method to assess vitamin A deficiency (n=375). And last we used the dietary intake data of children in the randomized controlled trial to model the potential contribution of yellow cassava to the nutrient adequacy of micronutrient intake using linear programming.

Results: The randomized controlled feeding trial collected complete data for 337 children with a compliance of 100%. Primary analyses (per protocol) showed that serum retinol concentrations in the yellow cassava group, increased with 0.04 μmol/L (95%CI: 0.00‒0.07 μmol/L) compared to the white cassava group and secondary analyses showed that serum β-carotene concentration increased with 524% (448%‒608%). No evidence of effect modification by initial vitamin A status, zinc status, or polymorphisms in the β-carotene monooxygenase gene was found. In the acceptability study 72% of caretakers and children were able to detect a significant difference in taste between white and yellow cassava and indicated to prefer yellow cassava because of its soft texture, sweet taste and attractive color. Serum concentrations of retinol binding protein, transthyretin and C-reactive protein combined showed excellent diagnostic performance in estimating vitamin A deficiency in primary school children, with an area under the curve of 0.98. Adding yellow cassava to the diet as a school lunch improved the nutrient adequacy of the diet of schoolchildren, however, even with the addition of nutrient dense foods such as fish and oil, nutrient adequacy could not be ensured for fat, riboflavin, niacin, folate and vitamin A.

Conclusions: Consumption of yellow cassava is acceptable and improves the serum retinol concentrations of primary school children in Kenya. The combination of three proxy markers is a promising approach to measure vitamin A deficiency in a low resource setting. Yellow cassava contributes to a better nutrient adequacy but should be accompanied by additional dietary guidelines and interventions to fill the remaining nutrient gaps.

Efficacy of iron fortified cowpea flour in improving iron status of schoolchildren in malaria endemic rural Ghana
Abizari, A.R. - \ 2013
University. Promotor(en): Michael Zimmermann, co-promotor(en): Inge Brouwer; M. Armar-Klemesu. - S.l. : s.n. - ISBN 9789461735263 - 191
vignameel - fortificatie - ijzer - ijzergebrekanemie - voedingstoestand - schoolkinderen - ghana - schoolmaaltijden - edta - biologische beschikbaarheid - voedingsprogramma - malaria - voedselsoevereiniteit - cowpea meal - fortification - iron - iron deficiency anaemia - nutritional state - school children - school meals - bioavailability - nutrition programmes - food sovereignty

Children in sub-Saharan Africa are more likely to have survived the critical first 1000 days of life carrying along unresolved micronutrient deficiencies into the school-age. Iron-deficiency is the most prevalent micronutrient problem affecting school-age children in sub-Saharan Africa and yet the most difficult to resolve. It is necessary to ensure an adequate iron intake through the diet of school-age children and school-based feeding intervention may be a way to improve iron intake of schoolchildren. Such a feeding intervention would be more sustainable if it relies on locally produced food(s) with the potential to support food sovereignty. In this context, this thesis investigated whether foods based on cowpeas, an indigenous legume crop originating from Africa, can be used in a school feeding setting to improve iron status of school-age children in Ghana.

The investigations in this thesis comprised cross-sectional dietary and iron status assessment of schoolchildren (n=383), cowpea acceptability among schoolchildren (n=120 mother-child pairs), chemical analysis of cowpea landraces (n=14), an in vivo iron bioavailability among young women (n=16) and a randomized cowpea intervention trial (n=241) conducted mainly in Tolon-Kumbungu district of Ghana.

The results indicated that iron-deficiency and iron-deficiency anaemia affect 8 and 7 out of every 10 schoolchildren respectively. It also showed that the probability of adequate dietary iron intake is 0.32 but much larger (~0.90) if schoolchildren benefitted from a school feeding programme. Mothers/caregivers intended to give cowpeas to their schoolchildren 2–3 times per week. The positive attitudes of mothers towards cowpea predicted their intention to give them to their schoolchildren but they were worried about the cost, long cooking time and the discomfort their children may suffer after consuming cowpeas. The chemical analysis showed that cowpeas contain appreciable amounts of iron (4.9–8.2 mg/ 100 gd.w) and zinc (2.7–4.1 mg/100 gd.w) but also high amounts of inhibitory phytate (477–1110 mg/100 gd.w) and polyphenol (327–1055 mg/100 gd.w). Polyphenol concentration in particular was higher (P<0.05) in coloured compared to white landraces. Iron bioavailability from red and white cowpeas were 1.4 and 1.7%, respectively, in NaFeEDTA-fortified meals and 0.89 and 1.2%, respectively, in FeSO4-fortified meals. Compared with FeSO4, fortification with NaFeEDTA increased the amount of iron absorbed from white and red cowpea meals by 0.05 and 0.08 mg (P < 0.05) respectively. Irrespective of the fortificant used, there was no significant difference in the amount of iron absorbed from the 2 varieties of cowpea. Finally the results from the intervention trial showed that fortification of whole cowpea flour with NaFeEDTA resulted in improvement of haemoglobin (P<0.05), serum ferritin (P<0.001) and body iron stores (P<0.001), and reduction in transferrin receptor concentration (P<0.001). Fortification also resulted in 30% and 47% reduction in the prevalence of iron-deficiency (ID) and iron-deficiency anaemia (IDA) (P<0.05), respectively.

Overall, this thesis has shown that in a malarious region with high iron-deficiency like (northern) Ghana, iron status of schoolchildren can be improved through the consumption of cowpeas within a school feeding programme. The improvement in iron status is however unlikely to result from the usual/conventional consumption of cowpeas but through fortification of whole cowpea flour with a highly bioavailable iron compound. This thesis has also shown that the most suitable iron compound for such whole cowpea flour fortification is NaFeEDTA irrespective of whether the cowpea has high or low concentration of polyphenols.

Youth, Nutrition and Behaviour
Voordouw, J. ; Snoek, H.M. ; Broek, E. van den; Reinders, M.J. ; Meeusen, M.J.G. ; Veggel, R.J.F.M. van; Kooijman, V.M. ; Stijnen, D.A.J.M. ; Trentelman, I. - \ 2012
Den Haag : LEI, onderdeel van Wageningen UR - 9
voeding en gezondheid - jeugd - schoollunches - gedrag - kinderen - schoolmaaltijden - schoolkinderen - schoolontbijten - nutrition and health - youth - school lunches - behaviour - children - school meals - school children - school breakfasts
Healthy nutrition is widely assumed to have a beneficial influence on educational performance and social behaviour. Yet research in developed countries about the effects of food intake on children's behaviour and school performance is limited. We propose a randomised controlled field experiment to study the effects of a school lunch programme in the Netherlands, based on an overview of studies by LEI and Food and Biobased Research, both part of Wageningen UR.
Report on Childhood Obesity in China (8): Effects and Sustainability of Physical Activity Intervention on Body Composition of Chinese Youth
Li, Y.P. ; Hu, X.Q. ; Schouten, E.G. ; Liu, A.L. ; Du, S.M. ; Li, L.Z. ; Cui, Z.H. ; Wang, D. ; Kok, F.J. ; Hu, F.B. ; Ma, G.S. - \ 2010
Biomedical and environmental sciences 23 (2010)3. - ISSN 0895-3988 - p. 180 - 187.
school children - mass index - overweight - prevention - health - adolescents - nutrition - programs - weight
Objectives To determine whether a large-scale physical activity intervention could affect body composition in primary school students in Beijing, China. Methods The study design was one-year cluster randomized controlled trial of physical activity intervention (20 min of daily exercise in the classroom) with an additional year of follow-up among 4 700 students aged 8-11 years at baseline. Results After the one-year intervention, BMI increased by 0.56 kg/m(2) (SD 1.15) in the intervention group and by 0.72 kg/m(2) (SD 1.20) in the control group, with a mean difference of -0.15 kg/m(2) (95% CI: -0.28 to -0.02). BMI z score decreased by -0.05 (SD 0.44) in the intervention group, but increased by 0.01 (SD 0.46) in the control group, with a mean difference of -0.07 (-0.13 10 -0.01). After another year of follow up, compared to the control group, children in the intervention group had significantly lower BMI (-0.13, -0.25 to -0.01), BMI z score (-0.05, -0.10 to -0.01), fat mass (-0.27 kg, -0.53 to -0.02) and percent body fat (-0.53, -1.00 to -0.05). The intervention had a more pronounced effect on weight, height, BMI, BMI z score, and body composition among obese children than among normal weight or overweight children. Compared to the control group, the intervention group had a significantly higher percentage of children who maintained or reduced their BMI z score at year 1 (P=0.008) and year 2 (P=0.04). Conclusions These findings suggest that 20 min of daily moderate to vigorous physical activity during the school year is a feasible and effective way to prevent excessive gain of body weight, BMI, and body fatness in primary school students.
Encouraging vegetable intake in children : the role of parental strategies, cognitive development and properties of food
Zeinstra, G.G. - \ 2010
University. Promotor(en): Kees de Graaf; Frans Kok, co-promotor(en): Maria Koelen. - [S.l. : S.n. - ISBN 9789085855385 - 200
groenten - voedselopname - voedselconsumptie - eten - kinderen - schoolkinderen - voedselvoorkeuren - ouderrol - cognitieve ontwikkeling - sensorische evaluatie - vegetables - food intake - food consumption - eating - children - school children - food preferences - parental role - cognitive development - sensory evaluation
Despite the health benefits, children’s fruit and vegetable intake is below that
recommended. This thesis focuses on the role of parental strategies, children’s
cognitive development and properties of food in order to develop new approaches
to increase fruit and vegetable preferences and intake in 4 to 12-year-old
First, we conducted a qualitative study (N=28) with three age groups representing
different cognitive developmental stages, and a parental survey study (N=242).
These studies indicated that texture was more important for 4-5-year-old
children’s food preferences than for 11-12-year olds and that the parental
strategy of ‘Choice’ was positively related to both children’s fruit and vegetable
intake. Subsequently, in three intervention studies, the focus was on vegetables
only, because previous approaches have been less effective for vegetable intake
than for fruit intake. We investigated three approaches for their effectiveness in
increasing children’s vegetable acceptance:
1. Varying the preparation method (4-12y; N=94): Carrots and French
beans were prepared in six ways: mashed, boiled, steamed, grilled,
stir-fried and deep-fried.
2. Flavour-nutrient learning (7-8y; N=19): During a 14-day learning
period, vegetable flavours were combined with energy (maltodextrin)
or without energy in a drink.
3. Choice-offering (4-6y; N=303): Children had no choice, a choice before
a meal, or a choice during a meal regarding which vegetable out of
two they were going to eat.
Varying the preparation method demonstrated that steamed and boiled were
preferred over the other preparations (p<0.05). Positive predictors of vegetable
liking were a uniform surface, the typical vegetable taste and crunchiness,
whereas brown colouring and a granular texture negatively predicted liking. Due
to insufficient consumption of the vegetable drinks (≈3 grams of 150 grams),
flavour-nutrient learning could not take place. The pure vegetable taste was too
intense. In the choice-offering study, the children appreciated a choice before the
meal, but the three conditions did not differ for vegetable liking (p=0.43) or intake
(≈52 gram; p=0.54). In the no-choice condition, high reactant children consumed
less vegetables than low reactant children (Δ=28 grams; p=0.04).
To encourage children’s vegetable liking and intake, the following approaches
may be most promising: 1) serve vegetables as crunchy as possible without
brown colouring or a granular texture; 2) provide children with choice during
vegetable eating; 3) stimulate a positive vegetable-eating context. Finally, serving
vegetables in mixed dishes is a good way to facilitate flavour-flavour and flavournutrient
learning, but the effectiveness of flavour-nutrient learning for increasing
children’s vegetable acceptance needs to be determined in future research.
Micronutrients, omega-3 fatty acids and cognitive performance in Indian schoolchildren
Eilander, J.H.C. - \ 2009
University. Promotor(en): Frans Kok, co-promotor(en): S.J.M. Osendarp; S. Muthayya. - [S.l. : S.n. - ISBN 9789085854708 - 175
sporenelementen - meervoudig onverzadigde vetzuren - cognitieve ontwikkeling - mentale vaardigheid - minerale supplementen - fortificatie - ondervoeding - schoolkinderen - india - omega-3 vetzuren - kenvermogen - trace elements - polyenoic fatty acids - cognitive development - mental ability - mineral supplements - fortification - undernutrition - school children - omega-3 fatty acids - cognition
Dertig dagen zonder televisie: mogelijkheden te over
Peters, K.B.M. ; Rijnierse, J. - \ 2007
Vrijetijdstudies 25 (2007)2. - ISSN 1384-2439 - p. 55 - 59.
massamedia - vrijetijdsactiviteiten - televisie - effecten - nadelige gevolgen - sociale gevolgen - lichamelijke opvoeding - studieresultaat - leerprestaties - geletterdheid - kinderen - schoolkinderen - nederland - mass media - leisure activities - television - effects - adverse effects - social impact - physical education - academic achievement - educational performance - literacy - children - school children - netherlands
Van kinderen in de leeftijd van 4-11 jaar kijkt bijna 60% meer dan 9 uur televisie per week. Nederlandse kinderen kijken gemiddeld 2 uur per dag naar de televisie. Het feit dat kinderen televisie kijken, krijgt veel aandacht vanwege de negatieve gevolgen die dit zou hebben op de ontwikkeling van kinderen. In deze bijdrage wordt uiteengezet wat kinderen gaan doen als ze nu eens 30 dagen geen televisie mogen kijken. Hoe beleven kinderen een dergelijke periode? Wat gaan ze doen als de tv niet meer aan mag? Dit artikel geeft de hoofdlijnen weer van Wagenings onderzoek
Anemia among school children in Vietnam: the efficacy of iron fortification
Thi Huong, Le - \ 2006
University. Promotor(en): Frans Kok, co-promotor(en): Inge Brouwer; K.C. NGuyen. - [S.l.] : S.n. - ISBN 908504541X - 159 p.
anemie - ijzergebrekanemie - ijzer - fortificatie - voedingstoestand - schoolkinderen - vietnam - bijvoeding - anaemia - iron deficiency anaemia - iron - fortification - nutritional state - school children - supplementary feeding
The present thesis aimed to determine the efficacy of a school-based food fortification program to improve hemoglobin concentrations and iron stores of intestinal parasites-prone school children. Furthermore this thesis also compares the effect of iron fortification and iron supplementation on the changes in hemoglobin and iron status.
Iodine deficiency and functional performance of schoolchildren in Benin
Briel-van Ingen, T. van den - \ 2001
University. Promotor(en): J.G.A.J. Hautvast; C.E. West; N. Bleichrodt. - S.l. : s.n.] - ISBN 9789058085368 - 160 p.
jodium - deficiëntie - prestatietests - mentale vaardigheid - gehoorgrens - schildklierfunctietoetsen - schoolkinderen - benin - iodine - deficiency - performance tests - mental ability - auditory threshold - thyroid function tests - school children
The notion that iodine deficiency may lead not only to goiter and cretinism, but to a much wider range of disorders, from stillbirth and abortions, to hearing problems and mental and physical underdevelopment began to be accepted beyond the research community since the early 1980's. In 1990 it was estimated that these problems, collectively called iodine deficiency disorders (IDD), presented a public health problem in 118 countries and that over 40 million people were affected by some degree of mental impairment. Children who have been exposed to iodine deficiency in the pre- and early post-natal phases of life show varying degrees of mental and psychomotor retardation, depending on the duration and degree of the deficiency. Adequate maternal iodine intake before and during pregnancy prevents such disorders. The question however whether or not deficits in mental and psychomotor performance of iodine deficient children may be reversed by supple-mentation with iodine later in life has not yet been answered unequivocally.</p><p>The research described in this thesis was set up to address this question. A double-blind placebo-controlled intervention was carried out in an iodine deficient area of northern Benin in the period 1995-1996. A single oral dose of iodized oil or placebo was administrated to 2 groups of schoolchildren, aged 7-11 years. The observation period was 10-11 months. However, 3 to 4 months after supple-mentation the population started to have access to iodized salt, in addition to non-iodized salt. Because iodine became available to both groups, the main hypothesis, i.e. that iodine supplementation would improve mental performance had to be modified. It was decided to take children whose iodine status, as measured by different indicators, did not change during the observation period as the "control" group. In addition to mental and psychomotor performance, other aspects associated with iodine deficiency were studied, including behavioral change and hearing thresholds and their relation with mental performance. The suitability of several indicators for measuring iodine status and thyroid function was evaluated.</p><p>Results showed that an improvement in iodine status as measured by urinary iodine concentration, was reflected in a significantly improved performance on the combination of mental tests, 10 months after supplementation. Moreover, children with better iodine status could hear better than their peers with a poorer iodine status, while hearing thresholds were negatively correlated with performance on all mental tests, but one. The serum concentration of thyroglobulin and the urinary iodine concentration were found to be indicators most suitable for measuring change in iodine status in this age group. Although the influx of iodine into the area precludes the drawing of "hard" conclusions, the results presented suggest that iodine supplementation is likely to promote a catch-up process in functional performance of iodine deficient schoolchildren.</p>
Meningen van kinderen over natuurverlies
Mabelis, A.A. - \ 1999
De Levende Natuur 100 (1999)7. - ISSN 0024-1520 - p. 230 - 235.
milieu - milieuafbraak - milieueffect - plattelandsjongeren - interacties - attitudes - kinderen - schoolkinderen - schade - destructie - nadelige gevolgen - bedreigde soorten - uitsterven - menselijke activiteit - karteringen - natuur - environment - environmental degradation - environmental impact - rural youth - interactions - children - school children - damage - destruction - adverse effects - endangered species - extinction - human activity - surveys - nature
Ongeveer 400 leerlingen van basisonderwijs en middelbaar onderwijs (MAVO en MAVO/VBO) in de regio Amerongen-Veenendaal werden geenqueteerd over hun gevoelens m.b.t. natuurverlies (uitsterven van soorten; bossterfte) en milieuverontreiniging (water-, bodem- en luchtverontreiniging; kernramp). Verder een inventarisatie van mogelijke afweerreacties t.a.v. negatieve info (selecteren; verdoven; bagatelliseren; vervormen)
Effect of iodine and iron supplementation on physical, psychomotor and mental development in primary school children in Malawi
Shrestha, R.M. - \ 1994
Agricultural University. Promotor(en): J.G.A.J. Hautvast; C.E. West; N. Bleichrodt. - S.l. : Shrestha - ISBN 9789054852346 - 105 p.
voedselhygiëne - voedingstoestand - consumptiepatronen - voedselsupplementen - voedingsstoornissen - jodium - ijzer - fysiologie - schoolkinderen - food hygiene - nutritional state - consumption patterns - food supplements - nutritional disorders - iodine - iron - physiology - school children
<p>Primary school children (n = 424) from the Ntcheu District, Malawi, aged 6 - 8 years, were selected for a double-blind placebo-controlled study to evaluate the effect of iodine and iron supplementation on physical, psychomotor and mental development. After the baseline measurements were carried out, children were given a single dose of iodized oil (1 mL Lipiodol®; 490 mg I) or placebo and daily doses of iron (ferrous sulphate, 60 mg of Fe) or placebo on weekdays (February-July and October- November 1991).<p>The anthropometric measurements included height, weight, mid-upper arm cicumference (MUAC), and four skinfolds while indicators of physical stamina included lung function, hand grip and sitting and standing ability. The psychomotor development tests were pegboard, ball throwing, tapping and reaction time tasks. The mental development tests included fluency and exclusion as a measure of fluid intelligence; quantity and verbal meaning to evaluate crystallized intelligence and visual memory and closure tests to measure perceptual skills. Baseline data were collected from October 1990 to January 1991 and the final tests and measurements were carried out in October-November 1991.<p>The initial iodine and iron status was established by measuring the concentration of iodine in urine and of hemoglobin in blood. About 86% of children had urinary iodine concentrations below 0.4 μmol/L indicating moderate iodine deficiency while 18% of children had hemoglobin levels below 110 g/L which is the cut-off point for indicating anemia. Measurement of iodine in urine three months after supplementation showed a normal level of urinary iodine. After one year, the level had dropped to the baseline value. The change in haemoglobin could not be measured due to objections from the parents in obtaining further blood samples. About 27% of children were stunted while 2% were wasted when measured at both time points.<p>One year after supplementation, the four treatment groups did not grow differentially indicating no effect of iodine or iron supplementation on physical growth. The iodinetreated group scored higher in tests of physical stamina as measured by sitting-standing and hand grip. The iodine treated group also significantly improved scores on the ball throwing exercise indicating an improvement in eye-hand coordination. No changes were noticed on reaction time, movement time and tapping indicating no effect of iodine on speed, dexterity and manual-motor coordination. The iron-treated group showed improvement only in eyehand coordination tests. No improvements were seen in other psychomotor tests.<p>Subjects in all four groups improved their scores on all mental development tests. The analysis of the placebo group indicated a considerable learning effect especially in fluency. Detailed analysis were conducted based upon the differential improvement when compared with the placebo group during the final test. The iodine-treated groups showed a large improvement in fluid intelligence measured by the fluency and exclusion tests. This component of intelligence measures reasoning, classification and fluency. Perceptual skills, as measured by visual memory and closure, also improved considerably in the iodine-treated group. Crystallized intelligence, as measured by quantity and verbal meaning, was also improved in the iodine-treated group but to a lesser extent than fluid intelligence. Crystallized intelligence is associated with word meaning, factual knowledge, short termmemory and decision making. These skills are closely associated with the classroom environment.<p>In the iron-treated group, a significant improvement was noted only in fluid intelligence and in the quantity test, a component of crystallized intelligence. No significant interaction of iodine and iron was noted. However, combined supplementation with iodine and iron sometimes resulted in an additive effect.<p>It has been shown in several studies in which iodine has been administered to mothers prior to pregnancy or during gestation that iodine supplementation reduces spontaneous abortion and stillbirths and improves the birth weight, and the mental and psychomotor performance of children. Previous studies in which children have been supplemented with iodine have not been able to demonstrate unequivocally that such supplementation affects mental or psychomotor development. In the present study we were able to demonstrate that iodine supplementation to children as old as 6-8 yr could improve mental and psychomotor development. The present study also demonstrates that iodine supplementation was more effective than iron supplementation in the population studied but the low prevalence of iron-deficiency anemia in children could have been responsible for such an outcome.<p>Concerning supplementation with iron, several previous studies have indicated that correction of iron deficiency early in infancy tends to improve psychomotor and mental development more than when the correction takes place in later life. In the present study, supplementation with iron was found to improve eye-hand coordination and fluid intelligence which justify prevention and control of iron-deficiency anemia in infants and children as soon as such a problem is detected.<p>An important finding from the perspective of planners is that 490 mg oral iodine may be inadequate to provide sufficient iodine for one year as indicated by the measurement of urinary iodine excretion. In iodine-deficient areas where provision of iodized salt is not available, the provision of iodized oil capsules could be an attractive alternative provided that the dosing schedule is adequate.
Buitenlandse studenten in het Nederlandse Hoger Onderwijs.
Snippe, J. ; Jochems, W.M.G. ; Bor, W. van den - \ 1994
Delft : Delftse Universitaire Pers - 108
hoger onderwijs - nederland - schoolkinderen - studenten - wereld - buitenlanders - higher education - netherlands - school children - students - world - foreigners
Acute effecten van perioden met verhoogde luchtverontreiniging in de buitenlucht op de luchtwegen van basisschoolkinderen in Nederland.
Hoek, G. ; Brunekreef, B. ; Hofschreuder, P. - \ 1992
Wageningen : Landbouwuniversiteit - 56
atmosfeer - aërosolen - samenstelling - stof - luchtverontreiniging - luchtkwaliteit - fysiologie - toxische stoffen - chemicaliën - ademhalingsziekten - schoolkinderen - nederland - milieuhygiëne - atmosphere - aerosols - composition - dust - air pollution - air quality - physiology - toxic substances - chemicals - respiratory diseases - school children - netherlands - environmental hygiene
Studentenbudget een boterham met tevredenheid?
Dickhoff, R.Th. ; Ophem, J.A.C. van; Vos, E.L. de - \ 1984
Vakblad voor Huishoudkunde 5 (1984). - p. 44 - 59.
budgetten - uitgaven voor consumptie - huishoudelijke consumptie - huishouduitgaven - inkomen - schoolkinderen - studenten - budgets - consumer expenditure - household consumption - household expenditure - income - school children - students
Onderzoek naar de sociaal-economische positie van verschillende kategorien Wageningse studenten in het studiejaar 1982-1983
Food intake, nutritional anthropometry and blood chemical parameters in 3 selected Dutch schoolchildren populations
Haar, F. van der; Kromhout, D. - \ 1978
Landbouwhogeschool Wageningen. Promotor(en): J.G.A.J. Hautvast. - Wageningen : Veenman - 239 p.
atherosclerose - bloed - chemische eigenschappen - antropologie - voeding - voedselhygiëne - voedingstoestand - consumptiepatronen - schoolkinderen - nederland - antropometrie - atherosclerosis - blood - chemical properties - anthropology - nutrition - food hygiene - nutritional state - consumption patterns - school children - netherlands - anthropometry
<p/>The major health problems in populations of economically developed countries at the present time are of a chronic nature with, as their main clinical characteristic, the frequently occurring premature coronary heart disease. When food intake data are to be evaluated, it would be incorrect in this situation to devote attention chiefly to the intake of essential nutrients. Instead, investigations into the food intake in these countries should currently be concerned in the first place with observed nutrient properties suspected of causing the development of elevated blood lipid levels in the majority of the individuals under study. This consideration was the most important point at issue during the performance, and presentation in this thesis, of a regional comparative study into the food intake and nutritional health status of 3 selected Dutch schoolchildren populations.<p/>The introduction starts with a short description of some recently conducted <em>in vitro</em> experiments investigating the role of lipoproteins in atherogenesis. Next, reviews are presented which cover fields of research related to the evaluation of associations between certain features of the life style and the incidence or mortality of atherosclerotic complications. One of these reviews was concerned with the socio-economic status, a very widely used index of life style, and its association with CHD death and CHD risk factors. It was concluded that the observed differences in CHD death and the relationship demonstrated to exist between socio-economic status, CHD death and CHD risk factors, strongly suggest environmental influences in the etiology of atherosclerosis. Diet, of course, is also one of the features of life style. The habitual diet of populations and, particularly, of individuals is difficult to characterize. The various dietary survey methods were the subject of an extensive review in an effort to assess the value of results to be expected from applying them in the collection of food intake data. It was concluded that, with due attention to survey period and number of participants, most dietary measurement techniques can be applied accurately enough to characterize the average diet of groups. If it is essential to assess accurately the individual's habitual diet, carefully conducted long lasting surveys will be needed. This conclusion was shown to have severe impact upon the objective of correlating nutrient composition of the individual's habitual diet to observed serum total cholesterol levels. The other argument used to demonstrate that zero correlation is the inevitable consequence of relating diet to serum total cholesterol within a population, has to do with the inaccuracy of characterizing individuals with respect to their serum total cholesterol level on the basis of single determinations. The variation in observed serum total cholesterol level was the subject of a further review. It was concluded that a single determination is insufficient to provide an accurate description of the individual's position in the observed distribution of serum total cholesterol determinations.<br/>Results from inter-population studies and from intervention trials were shown to be consistent with the saturated fat - serum cholesterol - CHD hypothesis. The conclusions reached in the foregoing reviews were reconciled with this hypothesis which may be shortly formulated as follows: a confluence of socio-economic and socio-cultural factors in industrialized countries, often indicated briefly with affluency, has led to the fact that the majority of the population now consumes an abundant diet. This diet, excessive in energy in relation to expenditure and rich in animal protein, saturated fat, cholesterol, sugar and salt, leads to a high prevalence of obesity and hyperlipidaemia in the population. Sustained hypercholesterolaemia markedly increases the probability of premature atherosclerotic disease in the population. In addition, a high prevalence of obesity often has the concomitant consequence of hypertension, hypertriglyceridaemia, etc. Thus, diet is related to the CHD epidemic through at least two identifiable changes of etio-pathological events. This justifies the designation of the current habitual diet as the decisive factor in the pathogenesis of the epidemic appearance of premature atherosclerotic disease.<br/>Of course, it is not the intention in this hypothesis to ignore the genetic contribution. It was formulated in the last review of the introduction that inheritance clearly primarily determines the question of whether or not a certain physiological status might be obtained, but that the environment moderates the extent to which the genetic make-up can express its potential. Although the simultaneous investigation of parents and children does not permit the disentangling of hereditary and environmental contributions, the practical consequences of observed familial resemblance in coronary risk factors would be the prediction of increased risk from elevated risk factor levels even in childhood and, at the same time, the justification of efforts aimed at reducing this risk. It has also been recognized that since the education towards the modern, affluent life style occurs during childhood, it is justified to include children into public recommendations intended to reduce the generally elevated risk factor levels in industrialized countries through modification of the diet in the whole community.<p/>The objective of the present study was to investigate whether differences in food intake data would lead to differences in nutritional health status, as measured by anthropometry and by blood lipids. Three comparative epidemiological surveys were carried out in the period 1974-1976 in schoolchildren between the ages of 3.5-13.5 from towns in different provinces of The Netherlands. Based on demographic data from the 1971 census the towns Heerenveen, Roermond and Harderwijk were chosen. In each town, schools with predominantly authochthonous children were selected by mutual arrangement with the local schoolphysician.<p/>Anthropometric measures and blood lipids were assessed in the participating schoolchildren and in parents from a sub-sample of these children. Food intake data were obtained from Grades 1-3 primary schoolchildren. Relationships between nutrient intake data and body fatness and between nutrient intake data and serum total cholesterol could be studied in these children. In another sub-sample, parent- child relationships concerning anthropometric data and blood lipids could be analysed.<p/>About 95% of the primary schoolchildren in Heerenveen and Harderwift participated in the survey. The participation rate was about 10% lower in Roermond. The participation rates in the nursery schools ranged between about 75 and 95 %. The participation rate among Heerenveen nursery schoolchildren was relatively low. The contacts with the parents of the nursery schoolchildren were intensified during the Roermond and Harderwift survey, resulting in higher participation rates among nursery schoolchildren in these towns.<p/>Demographic data about the education and occupation of the parents, socioeconomic status of the family and birth-places of parents and children was obtained by a general questionnaire filled in by the parents. The socio-economic status of the families tended to be highest in Roermond, intermediate in Heerenveen and lowest in Harderwift. However, the difference between Roermond and Heerenveen families seemed to be larger than the difference between Heerenveen and Harderwijk families. The difference between Roermond and the other towns may be explained by differences in the method of selection of schools. About 15% of the Heerenveen and Harderwift mothers were fully or part-time employed. In Roermond this percentage was twice as high. In Roermond about 2/3 of the parents was authochthonous compared to about 1/3 in Harderwift. In both Roermond and Harderwift about 2/3 of the examined children had been born and raised in the province of Limburg and the region of the North-west Veluwe respectively. During the Heerenveen survey information about the birth-places of parents and children was not obtained.<p/>The anthropometry included measuring of each child's body weight, standing height, knee widths, mid-arm muscle circumference and skinfold thicknesses at 4 sites - biceps, triceps, subscapular and suprailiac. Results of the measurements were adjusted to a joint level on the basis of comparison experiments, by correcting the mean level of measurements obtained in Heerenveen and Harderwijk children to the level of measurements observed for the regular Roermond investigator. Children from Heerenveen compared favourably to their agepeers from Roermond and Harderwift with respect to the anthropometric measurements. Frank obesity, tentatively defined to be present if estimates of body fatness based on skinfold thickness measurements exceeded 25-27%, was observed in 3.2 % of the Heerenveen children. Compared to these Heerenveen children, children from Roermond were found to be smaller and to have less skeletal and muscle mass, but. considerably more body fat. This was reflected by higher mean skinfold thicknesses and a higher prevalence of frank obesity, amounting to 6.0% of all Roermond children. Children from Harderwijk took the intermediate position with respect to body weight and standing height. Skeletal mass in children from Harderwijk was found to be roughly comparable to that in children from Heerenveen, but Harderwift children were found to have even less muscle mass than children from Roermond. At the mean level, children from Harderwift had the thickest subcutaneous fat layer but the prevalence of frank obesity found, 4.6%, was intermediate between that observed in children from Heerenveen and Roermond. A high dependence of the observed body weights in the children upon the examined anthropometric measures was demonstrated by multiple regression analysis. This finding was interpreted as a substantiation for the above-described comparisons. Comparison of the findings for the thickness of the subcutaneous fat layer in these Dutch children with figures reported for schoolchildren populations from other economically developed countries, reveals that these Dutch children generally exhibited lower skinfold thicknesses than their age-peers from the USA, Canada, England and West- Germany.<p/>The determinations in venous blood, obtained by a Vacutainer system while participants were in the fasting state, comprised the assessment of the concentrations of blood haemoglobin, serum total cholesterol and serum triglycerides. The determination of the serum HDL-cholesterol concentration was added to these during the execution of the Roermond and Harderwift projects. Results of serum total cholesterol and triglycerides determinations from the 3 project towns were adjusted to the level of measurement observed in a subsample of the collected sera by the Johns Hopkins University LRC Laboratory, which performed the determinations according to regulations of the international WHO Lipid Standardization Program under surveillance of the CDC Standardization Laboratory at Atlanta, Georgia. Results of the haemoglobin determinations in both boys and girls from all three towns were consistent with the well-known increase in haemoglobin concentration with age in schoolchildren. Girls were found to have a somewhat higher haemoglobin concentration than boys. The prevalence of clinical plus subclinical anaemia (haemoglobin &lt; 12.0 g/100 ml) was highest in children from Roermond and lowest in children from Harderwift. Only a very small number of children had clinical anaemia (Haemoglobin &lt; 11.0 g/100 ml) and it has consequently been concluded that the results of blood haemoglobin determinations have confirmed the assumption that the participating children belonged to the normal, healthy schoolchildren population from The Netherlands.<br/>Observed mean serum total cholesterol concentrations in boys and girls from the 3 towns varied between 160 and 190 mg/100 ml. Consistently lower values were observed in children from Heerenveen, compared to those from Roermond and Harderwift. Only in the Heerenveen children was the mean serum total cholesterol concentration positively related to age-categories. Girls had approximately 5 mg/100 ml higher mean concentrations than boys in all 3 towns. The overall prevalence of borderline plus frank cholesterolaemia (cholesterol>, 200 ing/ 100 ml) was found to be 19.5 % in boys and 24.8 % in girls.<br/>Frank hypercholesterolaemia (cholesterol>220 mg/100 ml) was present in 7.2% of all boys and in 9.8% of all girls. By both criteria, children from Heerenveen showed the lowest, and children from Harderwift the highest prevalence. However, the differences observed in prevalence of hypercholesterolaemia did not consistently reach statistical significance. Comparisons of the findings in these Dutch children with reported serum total cholesterol concentrations in children from other Western countries generally revealed that the levels in these Dutch children were among the highest reported. In addition, almost identical figures have been reported in adolescents from New Zealand and the USA.<br/>The observed mean triglycerides concentrations in boys and girls from the 3 towns varied between 55 and 75 mg/100 ml. Mean triglycerides concentrations in children from Harderwijk were about 10% lower than those in Roermond children. Heerenveen children were found to have only slightly lower mean concentrations than children from Roermond. Girls had approximately 4 mg/I 00 ml. higher mean serum triglycerides concentrations than boys in all 3 towns. No consistent relationship with age-category was observed. The prevalence of frank hypertriglyceridaemia, tentatively evaluated by the cut-off point of 100 mg/ 100 ml. was found to be 7.5 % in all boys and 7.1 % in all girls. Comparison of serum triglycerides concentrations with values reported in schoolchildren populations from other countries seems to indicate that the values found in these Dutch children were relatively low.<br/>The mean serum HDL-cholesterol concentrations in children from Roermond and Harderwijk were found to vary between 50 and 60 mg/100 ml. Only minor differences were observed in mean serum HDL-cholesterol concentrations between children from Roermond and Harderwift. In these schoolchildren about 1/3 of the serum total cholesterol was contained in the HDL. Although this percentage was highly variable between individual children, a positive association was found with age-categories in the 4 project-sex combinations.<p/>The examination of parents from a sub-sample of the participating children offered the possibility of comparing the level of measurements in fathers and mothers, both separately and by the combination of spouse pairs, to the levels observed in children. The same analysis was done for the measurements obtained among married couples and among siblings. Strong concordances in measurement levels for standing height, body fatness and blood chemical parameters were observed between married couples and their children. The same concordance was noted for all anthropometric and blood chemical parameters in the analysis of resemblance between siblings. If levels observed in parents were compared to those of their children for fathers and mothers separately and, moreover, for daughters and sons separately, the degree of resemblance became substantially smaller. The concordance of measurement levels between spouses seemed to be virtually absent. It was concluded from these observations that the position which the child takes in the distribution of examined characteristics must be on the polygenic control, and that the degree and nature of resemblance was in agreement with the concept of determination by both parents. In addition, it has been argued that the same environment shared by the first degree relatives must have contributed to the degree in which inheritance could have expressed its potential. It has been recognized that the repeatedly demonstrated familial resemblance in disease and the risk factors justified the inference of risk from elevated levels even in childhood and, at the same time, the justification for attempts to alter these risks in childhood.<p/>In all 3 towns statistically significant inverse associations were observed between the prevalence of obesity in the children and the educational level of the mother. Consistent inverse relationships between hypercholesterolaemia in children and the educational level of the father or mother and the socioeconomic status of the family were observed in Harderwift only. These data seem to indicate that nowadays elevated biological parameters are more prevalent in children from the lower social classes compared to children from the higher social classes. However, these associations could only be studied by making broad categories. More detailed studies are needed in order to corroborate these findings.<p/>Information about the food intake of the children was obtained by a two-day record filled in by the mother. This record was checked for completeness after the recording period, during an interview between the mother and one of the investigators. The percentage of children in which reliable dietary records were obtained ranged from 77 % in Heerenveen to 91 % in Harderwift. Co-operation was refused by the mothers of 8% of the Heerenveen children, 9% of the Roermond children and 3 % of the Harderwift children. It was concluded that the results of the dietary surveys were not profoundly influenced by the refusal rate.<p/>As suggested by previous studies, differences in food intake patterns between the children from the different towns could be observed. The percentage of children who ate cheese, yoghurt, sweet fruit squashes or breakfast cake (including 'Friese koek') was higher in Heerenveen compared to the other towns. The percentage of children who ate apple sauce or mean-PUFA low-fat margarines was lower in Heerenveen compared to the other towns. The percentage of children who ate mean-fat pork or French fried potatoes was higher and the percentage of children who ate peanut butter was lower in Roermond compared to the other towns. The percentage of children who drank low-fat milk or ate (whole) meal bread was higher, and the percentage of children who ate white bread was lower in Harderwift compared to the children in the other towns. These differences in food intake patterns led to some differences in nutrient intake data. However, from the energy percentage point of view these differences were very small.<p/>The energy intake of boys aged 6-10 was higher compared to that of girls of the same age. Consistent differences in energy intake between obese and lean children were not observed. These findings confirmed the results of other studies.<br/>Statistically significant relationships between nutrient intake data and serum total cholesterol level could not be found in the present study. Significant relationships between nutrient intake data and serum total cholesterol could be shown when the results of studies carried out in schoolchildren in the period 1946-1951 were included. These findings demonstrated that the relationship between nutrient intake data and serum total cholesterol was concealed when the range in these parameters was relatively small. When this range was increased, significant relationships reappear.<br/>Compared to the results of previous studies, the current diet of Dutch children is high in animal proteins, saturated fats, dietary cholesterol and oligosaccharides and low in polysaccharides, vegetable proteins and dietary fibre. Such a diet is known for its atherogenic properties and the results of the present study showed that hypercholesterolaemia, and to a lesser extent obesity, was present in a considerable percentage of children. It is known from prospective studies that the predictive power of CHD risk factors is inversely related to age. From these data it can be inferred that the effectiveness and efficiency of preventive measures could be increased if they are started in childhood.<br/>A prudent diet, low in animal proteins, saturated fats, dietary cholesterol and oligo-saccharides and high in polysaccharides, vegetable proteins and dietary fibre, compared to the current diet is recommended for the whole population in the prevention of CHD. Some investigators have also recommended such a diet in the prevention of cancer. It may be expected that if such a diet was used by the whole population, <em>including children</em> , <em></em> the burden of premature death from chronic diseases could be reduced. To prove this hypothesis by means of intervention trials is one of the major challenges in preventive health of the present time.<p/>
Het Onderwijs en het beroep van boerenzoons in het Drentse zandgebied
Tjoonk, L. - \ 1972
's-Gravenhage : [s.n.] (Streekonderzoek / LEI afd. 2, no. 43) - 32 p.
landbouw - beroepsopleiding - beroepsopleiding (hoger) - opleiding - carrièreontwikkeling - sociale mobiliteit - beroepskeuze - beroepen - schoolkinderen - nederland - drenthe - agriculture - vocational training - professional education - training - career development - social mobility - career choice - occupations - school children - netherlands
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