- Email: [email protected]
No choice vs free choice: How serving situations influence pre-school children’s vegetable intake
Food Quality and Preference 72 (2019) 172–176
Contents lists available at ScienceDirect
Food Quality and Preference journal homepage: www.elsevier.com/locate/foodqual
No choice vs free choice: How serving situations influence pre-school children’s vegetable intake
T
⁎
Annemarie Olsena, , Julia Christiane Sicka,b, Per Møllera,1, Helene Hausnera,2 a
3University of Copenhagen, Faculty of Science, Department of Food Science, Section for Design and Consumer Behaviour, Rolighedsvej 26, 1958 Frederiksberg C, Denmark b University of Florence, Department of Management of Agricultural, Food and Forestry Systems, Via Donizetti 6, 50144 Florence, Italy
A R T I C LE I N FO
A B S T R A C T
Keywords: Choice Children Vegetables Snack Eating behaviour
Background: Children’s vegetable intake is below the recommendations in many European countries. Parents and caregivers often struggle to find ways to encourage children’s vegetable and fruit intake. Aim: The aim of the study was to investigate whether offering a choice (in contrast to no choice) increases the intake of snack vegetables in pre-school children. Method: Children aged 2–6 years were offered three snack vegetables in different serving situations (two no choice situations and two free choice situations). Results: Choice offering did not have a positive influence on children’s vegetable intake. When making stimulispecific comparisons (per vegetable), none or even negative effects on vegetable intake were found with choice. Discussion: Choice offering does not appear very effective. Pre-school children might be too young for potential effects of choice offering to produce changes in vegetable consumption, but it may be more effective in older children or adolescents. The outcome of choice manipulations may also be affected by the number, type, and selection of target stimuli.
1. Introduction Children’s vegetable intake is below the recommendations in many European countries (Yngve et al., 2005). A poor diet low in vegetables and fruit can have negative effects on health including obesity and cancer. In contrast, eating a variety of vegetables and fruit can promote health maintenance and prevent chronic diseases (WHO, 2015). Parents and caregivers often struggle to find ways to encourage children’s vegetable and fruit intake to meet the dietary recommendations (Dennison, Rockwell, & Baker, 1998; Yngve et al., 2005). It has been suggested that giving children a choice might facilitate vegetable consumption. This strategy has been tested in a few studies and seems to have potential to positively contribute to children’s vegetable intake (de Wild, de Graaf, Boshuizen, & Jager, 2015; Roe, Meengs, Birch, & Rolls, 2013; Rohlfs Domínguez et al., 2013; Zeinstra, Renes, Koelen, Kok, & de Graaf, 2010). Generally, having a choice is part of satisfying the need for autonomy, which self-determination theories claim will promote an individual’s well-being and individuality (Véronneau, Koestner, & Abela,
2005). It has also been suggested as a contributor to children’s development of food and taste preferences (Cooke, 2007). In the context of vegetables, 73% of children aged 9–12 years indicated that they prefer to have a free choice rather than being served a particular food (Olsen, Ritz, Kramer, & Møller, 2012). This was supported by experimental studies investigating whether offering a choice had a positive effect on children’s vegetable and fruit intake (de Wild et al., 2015; Roe et al., 2013; Rohlfs Domínguez et al., 2013; Zeinstra, Renes, et al., 2010). Zeinstra, Renes, et al. (2010) found that 3–5 year-old children preferred to have free choice between two vegetables, although a difference in liking and intake of vegetables comparing three choice options could not be shown. Another study found that offering children a choice at the beginning of the meal and having two vegetables available during a meal, increased children’s vegetable intake compared to not having a choice (Rohlfs Domínguez et al., 2013). This was supported by findings showing an increased likelihood of selection and consumption of vegetables and fruit when offering children a variety of vegetables and fruit with free choice compared to offering a single snack without choice. In both choice conditions, fruits were preferred over vegetables
⁎
Corresponding author. E-mail address: [email protected] (A. Olsen). 1 Present address: Per Møller Consulting, Langemosevej 17, 2880 Bagsværd, Denmark. 2 Present address: ALK-Abelló, Global Pharmacovigilance & Clinical Development, Bøge Allé 1, 2970 Hørsholm, Denmark. https://doi.org/10.1016/j.foodqual.2018.10.011 Received 29 May 2018; Received in revised form 10 October 2018; Accepted 25 October 2018 Available online 26 October 2018 0950-3293/ © 2018 Elsevier Ltd. All rights reserved.
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specific order of each dummy or target stimuli was randomized.
(Roe et al., 2013). A study by de Wild et al. (2015) showed that offering a choice of two vegetables at dinner increased children’s vegetable intake compared to not offering a choice. Therefore, providing children with a choice could be an easily applicable and cost-effective way to help children increase the intake of healthy foods. Previous research points in the direction that choiceoffering seems to have potential to positively contribute to children’s vegetable intake (Roe et al., 2013; Rohlfs Domínguez et al., 2013), but only a few experimental studies have examined this effect and there have been conflicting results (DeCosta, Møller, Frøst, & Olsen, 2017). Offering a choice between two vegetables has been shown to have a positive effect (Zeinstra, Renes, et al., 2010), however, offering three or more alternatives have not been well investigated in children. Furthermore, children in Scandinavia consume a considerable amount of their vegetables raw (Yngve et al., 2005), and they are typically eaten as so-called snack vegetables, which have been demonstrated to be a familiar and frequently eaten serving among Danish children (Olsen et al., 2012). However, only a few studies specifically investigated choice offering of snack vegetables among children (de Wild et al., 2015; Roe et al., 2013). The aim of the current study was to investigate whether offering a choice (in contrast to no choice) increases the intake of snack vegetables in pre-school children when presented with three choice alternatives.
2.3. Study design The study consisted of seven visits for each nursery group with around two sessions scheduled per week (within-child design). At the first visit, hedonic evaluations were conducted, and the remaining six visits included choice versus no choice conditions. The data collection was conducted by trained assistants. The vegetables were served as an afternoon snack at the time the children were used to eat a snack. Children were instructed not to comment on the food and not to share any food. They were eating together in their usual groups to make the servings as natural to the children as possible. In the following section the procedures at each visit are described. This is also summarized in Table 1. The order of visits 2–4 were randomized between the four groups in which the children were organized. 2.3.1. Hedonic evaluations During visit 1, children were first explained about the procedures, and familiarized with the scale. Afterwards, familiarity [previous tasting; yes/no] and liking [5-point hedonic smiley scale anchored from super good to super bad; Chen, Resurreccion, & Paguio, 1995] of two dummy stimuli and three target stimuli were assessed. The children were encouraged to taste the various vegetables, but it was respected, if a child refused to taste a particular food. The children were told to point at the smiley representing their level of liking on a laminated scale. Children were offered water in a plastic cup in between the tastings to rinse their mouth. The hedonic evaluations took place in a quiet area of the day-care institution.
2. Methods 2.1. Participants Children were recruited from a local nursery in Copenhagen, Denmark. The children were organized into four groups in which they normally would eat and have their daily activities. Participation was voluntary. Staff and parents were thoroughly informed about the project, and parents gave written consent. Based on the study protocol, the study was found not to require formal ethical approval by the Danish National Committee on Biomedical Research Ethics.3
2.3.2. No choice conditions During visits 2–4, children were served one type of vegetable only: 100 g of either sugar snaps, snack carrots or baby corn. During visit 5, children were offered 33 g of each of the three vegetables (the no choice condition with a mix of stimuli). 2.3.3. Choice conditions During visit 6, children were free to choose a single stimulus (referred to as one type of vegetable) from three different vegetables, whereas in visit 7 they were free to choose from a mix of two vegetables (each 50 g) with three alternatives. The purpose of using two different choice options in the study was to investigate whether having a free choice with or without a variety of vegetables made a difference. The outcome variable at visit 2–7 was intake of individual vegetables measured in grams. This was assessed by pre- and post-weighing all types of vegetables in all serving containers, and to use markings on the containers. All visits with no choice were scheduled prior to visits with choice. This was done to prevent children from suddenly experiencing restraints, which could have had a negative influence on their intake. Additionally, this served to familiarize the children with the included vegetables prior to the choice visits, so the all children would be familiar with the included vegetable prior to the visits where they were to choose between them.
2.2. Pilot study and selection of target stimuli A pilot study was performed in another nursery with the aim to test the suitability of the intended target stimuli; sugar snaps, baby corn and snack carrots, which are typical, and generally liked snack vegetables in Denmark. 17 children were offered a combination of the three target stimuli (=a no choice situation with variety within the serving) with 35 g ( ± 5g) of each of the three vegetables, which were served as a mixture in one serving container, and the children were invited to eat as little or as much as the wanted. The mean intake of all vegetables ( ± SEM) was 40 g ( ± 7 g); distributed at 13 ± 3 g of sugar snaps, 11 ± 4 g of baby corn, and 16 ± 3 g of snack carrots. Based on these data, the same stimuli were used in the main study. To allow room for possible increases in intake, the serving size was set to 100 g for the main study. The vegetables were served in a clear serving container marked with the child’s name. At the first visit, an additional two “dummy stimuli”, namely cucumber slices and celery sticks, were included for training purposes to familiarize the children with the study procedure and use of hedonic scales with the help of trained assistants. The dummy stimuli were served first and the target stimuli were served last. However, the
2.4. Data analysis Data were analyzed using the statistical software R for Windows (version RStudio 1.1.414) at a significance level of p ≤ 0.05. The outcome variables were tested for normal distribution using the ShapiroWilks test. The familiarity of each stimulus was quantified as the frequency of children who scored a stimulus as familiar. Pearson’s chi-squared test was used to analyze whether familiarity affects specific vegetable intake. Mean ( ± SEM) liking of the stimuli were compared using Student’s t-test. The effect of liking on the total mean vegetable intake
3 In Denmark, the system around ethical approvals differ from most other countries: Only what is considered “biomedical research” require formal ethical approval. Studies on food preferences, choice and eating behavior do not fall into this category. When formal ethical approval is not required, it is not possible to apply for it. The rules are described at the committee’s webpage: http:// www.nvk.dk/english.
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Table 1 Experimental design. Visit
Choice condition
Stimuli
Exact servings
1
Hedonic evaluations
2 dummy stimuli, and 3 target stimuli
2 3 4
No choice
Single stimulus in randomized, balanced order
5
No Choice
Mixture of all stimuli
Cucumber, celery, sugar snaps, snack carrots, and baby corn 100 g sugar snaps OR 100 g snack carrots OR 100 g baby corn 33 g sugar snaps AND 33 g snack carrots AND 33 g baby corn 100 g sugar snaps OR 100 g snack carrots OR100 g baby corn 50 g sugar snaps and 50 g snack carrots OR 50 g sugar snaps and 50 g baby corn OR 50 g snack carrots and 50 g baby corn
6
Free choice
Single stimuli, 3 alternatives
7
Free choice
Mixture, 3 alternatives
Fig. 1. Stimuli-specific comparison between mean ± SEM intakes of the no choice conditions and free choice condition (visit 6) between single stimuli with three alternatives; n = number of children that consumed the stimulus. This is a paired comparison (using Wilcoxon signed rank tests), so only children present in both choice settings are included, therefore n is lower than the total sample.
and 4.3 ± 0.2, n = 53), while celery was somewhat unknown and disliked (48%, and 2.7 ± 0.2, n = 52–53). The stimuli were familiar to most of the children with familiarity percentages of 88% for snack carrots, 76% for baby corn, and 67% for sugar snaps (n = 45–50). Snack carrots were significantly more liked (4.3 ± 0.1, n = 51), than sugar snaps (3.3 ± 0.2, n = 51, p = 0.0001) and baby corn (3.6 ± 0.2, n = 52, p = 0.003), and there was no difference between the two latter (p = 0.27). The reason n is lower than the total sample is that some children were absent on the day of testing, and others did not want to taste the vegetables. Familiarity and liking did not show any effect on specific vegetable intake, but the liking of sugar snaps was shown to positively affect intake (p = 0.02) in the no choice condition (visit 2–4).
was analyzed for each choice condition via one-way analysis of variance (ANOVA) and a simple linear regression model. For each choice condition, the mean intake of stimuli was calculated and compared via paired Wilcoxon signed rank tests for paired data and Mann-Whitney U tests for unpaired data. Non-parametric statistics were chosen as the data were shown not to be normally distributed. Total mean intake across all choice conditions was tested by using one-way ANOVA with Tukey’s test as a post hoc test. To enable comparisons of intake of each of the three vegetables between test days where different amounts were served, intake levels were adjusted to comparative levels prior to data analyses. The mean total vegetable intake was calculated for each choice condition excluding the no choice condition with a mix of stimuli (visit 5). Pearson’s chi-squared test was used to analyze differences in gender and total mean vegetable intake for each choice condition. Effects of age on total mean vegetable intake were analyzed via one-way analysis of covariance (ANCOVA) and a simple linear regression model.
3.3. Stimuli-specific comparison Children’s intake of vegetables in visits that are directly comparable, i.e. the no choice condition with one stimuli (visit 2–4) and the free choice condition with one stimuli (visit 6) is shown in Fig. 1. For snack carrots, the intake was significantly higher in the no choice condition compared to the free choice condition (p = 0.002). For sugar snaps and baby corn, the intake was comparable in both conditions, and there were no significant differences. When comparing intake at these visits across the entire sample (using Mann-Whitney U tests), similar levels were found: Snack carrot (73.2 ± 4.2, n = 65 vs 65.5 ± 4.4, n = 46), sugar snaps (26.5 ± 3.3, n = 66 vs 42.8 ± 9.4, n = 12), and baby corn (36.4 ± 4.5, n = 65 vs 36.7 ± 10.7, n = 9). No significant differences were found between conditions, but carrot intake tended to be highest in the no choice condition (p = 0.09), while sugar snaps intake tended to be highest in the free choice condition (p = 0.06). Comparable findings were found when comparing the adjusted intake in the no choice conditions (visit 2–4) to the intake in the free choice condition with a mix of vegetables with three alternatives (visit 7) (using Wilcoxon signed rank tests). The mean intake of carrots was significantly higher in the no choice condition compared to the free choice mixture option (36.4 ± 2.5 vs 32.4 ± 2.6, n = 46, p = 0.05). For sugar snaps (16.4 ± 3.1 vs 16.1 ± 2.7, n = 24) and baby corn (15.8 ± 4.1 vs 12 ± 3.2, n = 22), there were no significant differences by choice condition.
3. Results 3.1. Participant characteristics The study included 86 children aged 2–6 years (50 boys and 36 girls). The characteristics of the children are shown in Table 2. 3.2. Familiarity and liking For the dummy stimuli, cucumber was familiar and liked (100%, Table 2 Description of participants. Child Characteristics Sex Male Female
% (N) 58 (50) 42 (36)
Age Child age in months
Mean ± SD 49 ± 11
3.4. Comparison of total vegetable intake The mean total vegetable intake was significantly higher (p = 0.04) in the free choice condition (visit 6, 57.5 ± 4) compared to the no choice conditions with single stimuli and three choice alternatives (visit 174
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have included in a vegetable subscription service, 86% preferred 3 or more different types (Olsen et al., 2012). However, children can only eat a very limited amount and are not typically served a wide range of options, which would also result in food waste, so a few options may be the best trade-off, but that remains to be determined experimentally. Fifth, the children were rather young (2–6 years) and may lack the cognitive development to fully understand the distinct choice options. Children in the pre-operational stage (2–7 years) do not have the ability to use logical reasoning (Piaget, 1964) and therefore choice manipulation may be more effective in older children or adolescents (de Wild et al., 2015; Warren, Parry, Lynch, & Murphy, 2008). In addition, young children are not necessarily used to having a free choice and may not appreciate this option, which could explain the significant age effect in the no choice condition. Although it has previously been shown that choice offering may enhance intrinsic motivation in children (Patall, Cooper, & Robinson, 2008; Ryan & Deci, 2000), followed by experience of autonomy and facilitation of greater overall vegetable intake (DeCosta et al., 2017), this might only be the case for children of older age. It is also possible that, in young children, choice offering may have positive effects on qualitative parameters only (e.g. appreciation), which were thus not measurable in this study using intake as a quantitative outcome parameter. Sixth, study setting and consumption context can determine children’s food choices. Studies conducted in natural settings have found a positive effect on choice in 4–6-year olds (Rohlfs Domínguez et al., 2013). A strength of this study was its setting in the nursery that was familiar to the children and where they were regularly offered vegetables as an afternoon snack. Zeinstra. Koelen, et al. (2010a), Zeinstra, Renes, et al. (2010) investigated the effect of choice-offering in a restaurant setting, where children were more excited about the restaurant setting than expected, which may have biased the effect of choice offering. It would be useful to compare different settings (e.g. home, day care, school, dining out/restaurant). Seventh, choice offering may work best in combination with certain other approaches to changing children’s eating behavior, possibly nudging and choice architecture, which may be useful tools to encourage healthy choices in children by providing an environment that influences food choices just by its design (Thaler, Sunstein, & Balz, 2014). It is worth commenting upon the low vegetable intake on the day with bonfire pancakes. These data clearly demonstrate that children are interested in eating snack vegetables in general, but to a much lesser extent if they know that more palatable foods are available. This is important knowledge when designing future choice alternatives. Finally, strengths which should be mentioned to supplement the above, are the assessment of intake of each individual vegetable type for each child at each visit, the individually conducted hedonic evaluations, and the use of snack vegetables that were familiar and wellliked. Limitations include the order of the visits; it may have been better to fully randomize visits, instead of having choice visits before no choice visits. The sample size was comparable to other studies, but as there were always some children absent at the visits, findings may have been more robust with a larger sample with more power. Also, the children were all from the same nursery, which was located in an urban area, so results may not extrapolate to children in more rural areas. Although children were instructed not to comment upon their food, they were not able to completely follow this instruction due to their young age, which means that some peer influence did occur. In conclusion, choice offering did not have a positive influence on vegetable consumption in 2–6 year-old pre-school children. Future studies should reveal whether this finding is linked to children’s age, setting, or choice of target stimuli, and whether there may be positive effects on more qualitative outcome parameters.
2–4 combined, 45.6 ± 3.1), which did not differ significantly from the free choice condition with a mix of two stimuli and three choice alternatives (visit 7, 48.2 ± 3.1). When comparing the two free choice conditions, children consumed more vegetables when eating their choice of vegetables as a single stimuli (57.5 ± 4) compared to the option with a mix of two stimuli (48.2 ± 3.1), but the difference was not significant. Age was shown to positively affect total mean vegetable intake in the no choice conditions (visit 2–4, p = 0.01), demonstrating that with increasing age children increased their mean total vegetable intake. No gender effects were found on the total vegetable intake. Results from the no choice condition with mix of stimuli (visit 5, n = 62, 27.1 ± 2.6) were excluded from any statistical analysis as the nursery teachers unintendedly changed the study setting that day (they made bonfire pancakes, which the children could see throughout the vegetable visit, and which they would receive right after they finished their vegetable serving, so most children were less interested in the vegetable servings that day). 4. Discussion The current study demonstrated none or even negative effects of offering pre-school children a free choice of snack vegetables when looking at stimuli-specific comparisons of intake (Fig. 1). However, choice offering had a positive effect when comparing the total vegetable intake across conditions with a single stimulus, but not with a mix of two stimuli. These somewhat contradictory results contribute to the mixed findings in previous choice studies in children, and there are several possible explanations to both the present finding and the fact that this seems to be an area with conflicting findings. First, the differences between the two types of analyses may be partly explained by a difference in the number of children participating in the analyses. In the direct comparisons (Fig. 1) only children attending both sessions are included, and only few children chose sugar snaps and baby corn when given a free choice with a single stimulus (visit 6), making these comparisons less robust. Accordingly, the positive effects of choice on overall intake seem to be caused by a relatively high intake of sugar snaps among a small group of children in the choice condition. Thus, this finding seems closely linked to stimulus type. From the results, it is also clear that intake within choice conditions varies considerably across the three stimuli types. This implies that stimuli-specific comparisons may more directly reflect the influence of choice per se, and may thus be more reliable than comparisons across different stimuli. Second, although the serving size was constant across visits (100 g), the amount of the different types of vegetables varied at visit 5–7 with mixed stimuli. It is possible that this may have influenced children’s perception of portion size or perceived variety – both parameters that have been shown to influence intake (Bergamaschi et al., 2016; Fisher, Arreola, Birch, & Rolls, 2007). Third, the selection of stimuli could affect how many vegetables that are consumed (Zeinstra, Koelen, Kok, & de Graaf, 2010). The present study investigated the intake of three raw vegetables, namely snack carrots, sugar snaps and baby corn, which only represent a limited range of vegetables typically consumed by children. As most studies have worked with specific choice sets it is questionable whether findings are solely due to the choice settings or to the specific vegetables included in the studies (i.e. factors linked to liking and familiarity of these). It is also not clear whether there are some food categories (e.g. fruit, meat or dairy) where choice is more appreciated than others. Fourth, the number of choice options presented at a time may moderate effects of choice offering. In adults, this has indeed been shown (Iyengar, 2010). For instance, when choosing among jams, a small selection was proven to be more effective than a wide selection among adult consumers when it comes to subsequent purchases and product satisfaction (Iyengar & Lepper, 2000). When 9–12 year old children were asked about how many vegetables they would like to 175
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Acknowledgements
of a good thing? Journal of Personality and Social Psychology, 79, 995–1006. Olsen, A., Ritz, C., Kramer, L., & Møller, P. (2012). Serving styles of raw snack vegetables. What do children want? Appetite, 59, 556–562. Patall, E. A., Cooper, H., & Robinson, J. C. (2008). The effects of choice on intrinsic motivation and related outcomes: A meta-analysis of research findings. Psychological Bulletin, 134, 270–300. Piaget, J. (1964). Part I: Cognitive development in children: Piaget development and learning. Journal of Research in Science Teaching, 2, 176–186. Roe, L. S., Meengs, J. S., Birch, L. L., & Rolls, B. J. (2013). Serving a variety of vegetables and fruit as a snack increased intake in preschool children. The American Journal of Clinical Nutrition, 98, 693–699. Rohlfs Domínguez, P., Gámiz, F., Gil, M., Moreno, H., Márquez Zamora, R., Gallo, M., & de Brugada, I. (2013). Providing choice increases children’s vegetable intake. Food Quality and Preference, 30, 108–113. Ryan, R. M., & Deci, E. L. (2000). Self-determination theory and the facilitation of intrinsic motivation, social development, and well-being. The American Psychologist, 55, 68–78. Thaler, R. H., Sunstein, C. R., & Balz, J. P. (2014). Choice architecture. SSRN Electronic Journal. https://doi.org/10.2139/ssrn.2536504. Véronneau, M., Koestner, R. F., & Abela, J. R. Z. (2005). Intrinsic need satisfaction and well-being in children and adolescents: An application of the self-determination theory. Journal of Social and Clinical Psychology, 24, 280–292. Warren, E., Parry, O., Lynch, R., & Murphy, S. (2008). “If I don’t like it then I can choose what I want”: Welsh school children’s accounts of preference for and control over food choice. Health Promotion International, 23, 144–151. WHO (2015). Promoting fruit and vegetable consumption around the world. Retrieved February 14, 2018, fromhttp://www.who.int/dietphysicalactivity/fruit/en/index2. html. Yngve, A., Wolf, A., Poortvliet, E., Elmadfa, I., Brug, J., Ehrenblad, B., ... Klepp, K.-I. (2005). Fruit and vegetable intake in a sample of 11-year-old children in 9 European countries: The pro children cross-sectional survey. Annals of Nutrition & Metabolism, 49, 236–245. Zeinstra, G. G., Koelen, M. A., Kok, F. J., & de Graaf, C. (2010a). The influence of preparation method on children’s liking for vegetables. Food Quality and Preference, 21, 906–914. Zeinstra, G. G., Renes, R. J., Koelen, M. A., Kok, F. J., & de Graaf, C. (2010b). Offering choice and its effect on Dutch children’s liking and consumption of vegetables: A randomized controlled trial. The American Journal of Clinical Nutrition, 91, 349–356.
The study was funded by the European Community’s Seventh Framework Programme (FP7/2007-2013) under the Grant Agreement No. FP7-245012-HabEat. The research received supplementary funding from the Taste for Life project, which is financed by the Nordea Foundation. The authors report no conflicts of interest. Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.foodqual.2018.10.011. References Bergamaschi, V., Olsen, A., Laureati, M., Zangenberg, S., Pagliarini, E., & Bredie, W. L. P. (2016). Variety in snack servings as determinant for acceptance in school children. Appetite. Chen, A. W., Resurreccion, A. V. A., & Paguio, L. P. (1995). Age appropriate hedonic scales to measure food preferences of young children. Journal of Sensory Studies, 11(1996), 141–163. Cooke, L. (2007). The importance of exposure for healthy eating in childhood: A review. Journal of Human Nutrition and Dietetics, 20, 294–301. de Wild, V. W. T., de Graaf, C., Boshuizen, H. C., & Jager, G. (2015). Influence of choice on vegetable intake in children: An in-home study. Appetite, 91, 1–6. DeCosta, P., Møller, P., Frøst, M. B., & Olsen, A. (2017). Changing children’s eating behaviour – A review of experimental research. Appetite, 113, 327–357. Dennison, B. A., Rockwell, H. L., & Baker, S. L. (1998). Fruit and vegetable intake in young children. Journal of the American College of Nutrition, 17, 371–378. Fisher, J. O., Arreola, A., Birch, L. L., & Rolls, B. J. (2007). Portion size effects on daily energy intake in low-income Hispanic and African American children and their mothers. The American Journal of Clinical Nutrition. Iyengar, S. (2010). The art of choosing. Art of Choosing, 1–6. Iyengar, S., & Lepper, M. (2000). When choice is demotivating: Can one desire too much
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Contents lists available at ScienceDirect
Food Quality and Preference journal homepage: www.elsevier.com/locate/foodqual
No choice vs free choice: How serving situations influence pre-school children’s vegetable intake
T
⁎
Annemarie Olsena, , Julia Christiane Sicka,b, Per Møllera,1, Helene Hausnera,2 a
3University of Copenhagen, Faculty of Science, Department of Food Science, Section for Design and Consumer Behaviour, Rolighedsvej 26, 1958 Frederiksberg C, Denmark b University of Florence, Department of Management of Agricultural, Food and Forestry Systems, Via Donizetti 6, 50144 Florence, Italy
A R T I C LE I N FO
A B S T R A C T
Keywords: Choice Children Vegetables Snack Eating behaviour
Background: Children’s vegetable intake is below the recommendations in many European countries. Parents and caregivers often struggle to find ways to encourage children’s vegetable and fruit intake. Aim: The aim of the study was to investigate whether offering a choice (in contrast to no choice) increases the intake of snack vegetables in pre-school children. Method: Children aged 2–6 years were offered three snack vegetables in different serving situations (two no choice situations and two free choice situations). Results: Choice offering did not have a positive influence on children’s vegetable intake. When making stimulispecific comparisons (per vegetable), none or even negative effects on vegetable intake were found with choice. Discussion: Choice offering does not appear very effective. Pre-school children might be too young for potential effects of choice offering to produce changes in vegetable consumption, but it may be more effective in older children or adolescents. The outcome of choice manipulations may also be affected by the number, type, and selection of target stimuli.
1. Introduction Children’s vegetable intake is below the recommendations in many European countries (Yngve et al., 2005). A poor diet low in vegetables and fruit can have negative effects on health including obesity and cancer. In contrast, eating a variety of vegetables and fruit can promote health maintenance and prevent chronic diseases (WHO, 2015). Parents and caregivers often struggle to find ways to encourage children’s vegetable and fruit intake to meet the dietary recommendations (Dennison, Rockwell, & Baker, 1998; Yngve et al., 2005). It has been suggested that giving children a choice might facilitate vegetable consumption. This strategy has been tested in a few studies and seems to have potential to positively contribute to children’s vegetable intake (de Wild, de Graaf, Boshuizen, & Jager, 2015; Roe, Meengs, Birch, & Rolls, 2013; Rohlfs Domínguez et al., 2013; Zeinstra, Renes, Koelen, Kok, & de Graaf, 2010). Generally, having a choice is part of satisfying the need for autonomy, which self-determination theories claim will promote an individual’s well-being and individuality (Véronneau, Koestner, & Abela,
2005). It has also been suggested as a contributor to children’s development of food and taste preferences (Cooke, 2007). In the context of vegetables, 73% of children aged 9–12 years indicated that they prefer to have a free choice rather than being served a particular food (Olsen, Ritz, Kramer, & Møller, 2012). This was supported by experimental studies investigating whether offering a choice had a positive effect on children’s vegetable and fruit intake (de Wild et al., 2015; Roe et al., 2013; Rohlfs Domínguez et al., 2013; Zeinstra, Renes, et al., 2010). Zeinstra, Renes, et al. (2010) found that 3–5 year-old children preferred to have free choice between two vegetables, although a difference in liking and intake of vegetables comparing three choice options could not be shown. Another study found that offering children a choice at the beginning of the meal and having two vegetables available during a meal, increased children’s vegetable intake compared to not having a choice (Rohlfs Domínguez et al., 2013). This was supported by findings showing an increased likelihood of selection and consumption of vegetables and fruit when offering children a variety of vegetables and fruit with free choice compared to offering a single snack without choice. In both choice conditions, fruits were preferred over vegetables
⁎
Corresponding author. E-mail address: [email protected] (A. Olsen). 1 Present address: Per Møller Consulting, Langemosevej 17, 2880 Bagsværd, Denmark. 2 Present address: ALK-Abelló, Global Pharmacovigilance & Clinical Development, Bøge Allé 1, 2970 Hørsholm, Denmark. https://doi.org/10.1016/j.foodqual.2018.10.011 Received 29 May 2018; Received in revised form 10 October 2018; Accepted 25 October 2018 Available online 26 October 2018 0950-3293/ © 2018 Elsevier Ltd. All rights reserved.
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specific order of each dummy or target stimuli was randomized.
(Roe et al., 2013). A study by de Wild et al. (2015) showed that offering a choice of two vegetables at dinner increased children’s vegetable intake compared to not offering a choice. Therefore, providing children with a choice could be an easily applicable and cost-effective way to help children increase the intake of healthy foods. Previous research points in the direction that choiceoffering seems to have potential to positively contribute to children’s vegetable intake (Roe et al., 2013; Rohlfs Domínguez et al., 2013), but only a few experimental studies have examined this effect and there have been conflicting results (DeCosta, Møller, Frøst, & Olsen, 2017). Offering a choice between two vegetables has been shown to have a positive effect (Zeinstra, Renes, et al., 2010), however, offering three or more alternatives have not been well investigated in children. Furthermore, children in Scandinavia consume a considerable amount of their vegetables raw (Yngve et al., 2005), and they are typically eaten as so-called snack vegetables, which have been demonstrated to be a familiar and frequently eaten serving among Danish children (Olsen et al., 2012). However, only a few studies specifically investigated choice offering of snack vegetables among children (de Wild et al., 2015; Roe et al., 2013). The aim of the current study was to investigate whether offering a choice (in contrast to no choice) increases the intake of snack vegetables in pre-school children when presented with three choice alternatives.
2.3. Study design The study consisted of seven visits for each nursery group with around two sessions scheduled per week (within-child design). At the first visit, hedonic evaluations were conducted, and the remaining six visits included choice versus no choice conditions. The data collection was conducted by trained assistants. The vegetables were served as an afternoon snack at the time the children were used to eat a snack. Children were instructed not to comment on the food and not to share any food. They were eating together in their usual groups to make the servings as natural to the children as possible. In the following section the procedures at each visit are described. This is also summarized in Table 1. The order of visits 2–4 were randomized between the four groups in which the children were organized. 2.3.1. Hedonic evaluations During visit 1, children were first explained about the procedures, and familiarized with the scale. Afterwards, familiarity [previous tasting; yes/no] and liking [5-point hedonic smiley scale anchored from super good to super bad; Chen, Resurreccion, & Paguio, 1995] of two dummy stimuli and three target stimuli were assessed. The children were encouraged to taste the various vegetables, but it was respected, if a child refused to taste a particular food. The children were told to point at the smiley representing their level of liking on a laminated scale. Children were offered water in a plastic cup in between the tastings to rinse their mouth. The hedonic evaluations took place in a quiet area of the day-care institution.
2. Methods 2.1. Participants Children were recruited from a local nursery in Copenhagen, Denmark. The children were organized into four groups in which they normally would eat and have their daily activities. Participation was voluntary. Staff and parents were thoroughly informed about the project, and parents gave written consent. Based on the study protocol, the study was found not to require formal ethical approval by the Danish National Committee on Biomedical Research Ethics.3
2.3.2. No choice conditions During visits 2–4, children were served one type of vegetable only: 100 g of either sugar snaps, snack carrots or baby corn. During visit 5, children were offered 33 g of each of the three vegetables (the no choice condition with a mix of stimuli). 2.3.3. Choice conditions During visit 6, children were free to choose a single stimulus (referred to as one type of vegetable) from three different vegetables, whereas in visit 7 they were free to choose from a mix of two vegetables (each 50 g) with three alternatives. The purpose of using two different choice options in the study was to investigate whether having a free choice with or without a variety of vegetables made a difference. The outcome variable at visit 2–7 was intake of individual vegetables measured in grams. This was assessed by pre- and post-weighing all types of vegetables in all serving containers, and to use markings on the containers. All visits with no choice were scheduled prior to visits with choice. This was done to prevent children from suddenly experiencing restraints, which could have had a negative influence on their intake. Additionally, this served to familiarize the children with the included vegetables prior to the choice visits, so the all children would be familiar with the included vegetable prior to the visits where they were to choose between them.
2.2. Pilot study and selection of target stimuli A pilot study was performed in another nursery with the aim to test the suitability of the intended target stimuli; sugar snaps, baby corn and snack carrots, which are typical, and generally liked snack vegetables in Denmark. 17 children were offered a combination of the three target stimuli (=a no choice situation with variety within the serving) with 35 g ( ± 5g) of each of the three vegetables, which were served as a mixture in one serving container, and the children were invited to eat as little or as much as the wanted. The mean intake of all vegetables ( ± SEM) was 40 g ( ± 7 g); distributed at 13 ± 3 g of sugar snaps, 11 ± 4 g of baby corn, and 16 ± 3 g of snack carrots. Based on these data, the same stimuli were used in the main study. To allow room for possible increases in intake, the serving size was set to 100 g for the main study. The vegetables were served in a clear serving container marked with the child’s name. At the first visit, an additional two “dummy stimuli”, namely cucumber slices and celery sticks, were included for training purposes to familiarize the children with the study procedure and use of hedonic scales with the help of trained assistants. The dummy stimuli were served first and the target stimuli were served last. However, the
2.4. Data analysis Data were analyzed using the statistical software R for Windows (version RStudio 1.1.414) at a significance level of p ≤ 0.05. The outcome variables were tested for normal distribution using the ShapiroWilks test. The familiarity of each stimulus was quantified as the frequency of children who scored a stimulus as familiar. Pearson’s chi-squared test was used to analyze whether familiarity affects specific vegetable intake. Mean ( ± SEM) liking of the stimuli were compared using Student’s t-test. The effect of liking on the total mean vegetable intake
3 In Denmark, the system around ethical approvals differ from most other countries: Only what is considered “biomedical research” require formal ethical approval. Studies on food preferences, choice and eating behavior do not fall into this category. When formal ethical approval is not required, it is not possible to apply for it. The rules are described at the committee’s webpage: http:// www.nvk.dk/english.
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Table 1 Experimental design. Visit
Choice condition
Stimuli
Exact servings
1
Hedonic evaluations
2 dummy stimuli, and 3 target stimuli
2 3 4
No choice
Single stimulus in randomized, balanced order
5
No Choice
Mixture of all stimuli
Cucumber, celery, sugar snaps, snack carrots, and baby corn 100 g sugar snaps OR 100 g snack carrots OR 100 g baby corn 33 g sugar snaps AND 33 g snack carrots AND 33 g baby corn 100 g sugar snaps OR 100 g snack carrots OR100 g baby corn 50 g sugar snaps and 50 g snack carrots OR 50 g sugar snaps and 50 g baby corn OR 50 g snack carrots and 50 g baby corn
6
Free choice
Single stimuli, 3 alternatives
7
Free choice
Mixture, 3 alternatives
Fig. 1. Stimuli-specific comparison between mean ± SEM intakes of the no choice conditions and free choice condition (visit 6) between single stimuli with three alternatives; n = number of children that consumed the stimulus. This is a paired comparison (using Wilcoxon signed rank tests), so only children present in both choice settings are included, therefore n is lower than the total sample.
and 4.3 ± 0.2, n = 53), while celery was somewhat unknown and disliked (48%, and 2.7 ± 0.2, n = 52–53). The stimuli were familiar to most of the children with familiarity percentages of 88% for snack carrots, 76% for baby corn, and 67% for sugar snaps (n = 45–50). Snack carrots were significantly more liked (4.3 ± 0.1, n = 51), than sugar snaps (3.3 ± 0.2, n = 51, p = 0.0001) and baby corn (3.6 ± 0.2, n = 52, p = 0.003), and there was no difference between the two latter (p = 0.27). The reason n is lower than the total sample is that some children were absent on the day of testing, and others did not want to taste the vegetables. Familiarity and liking did not show any effect on specific vegetable intake, but the liking of sugar snaps was shown to positively affect intake (p = 0.02) in the no choice condition (visit 2–4).
was analyzed for each choice condition via one-way analysis of variance (ANOVA) and a simple linear regression model. For each choice condition, the mean intake of stimuli was calculated and compared via paired Wilcoxon signed rank tests for paired data and Mann-Whitney U tests for unpaired data. Non-parametric statistics were chosen as the data were shown not to be normally distributed. Total mean intake across all choice conditions was tested by using one-way ANOVA with Tukey’s test as a post hoc test. To enable comparisons of intake of each of the three vegetables between test days where different amounts were served, intake levels were adjusted to comparative levels prior to data analyses. The mean total vegetable intake was calculated for each choice condition excluding the no choice condition with a mix of stimuli (visit 5). Pearson’s chi-squared test was used to analyze differences in gender and total mean vegetable intake for each choice condition. Effects of age on total mean vegetable intake were analyzed via one-way analysis of covariance (ANCOVA) and a simple linear regression model.
3.3. Stimuli-specific comparison Children’s intake of vegetables in visits that are directly comparable, i.e. the no choice condition with one stimuli (visit 2–4) and the free choice condition with one stimuli (visit 6) is shown in Fig. 1. For snack carrots, the intake was significantly higher in the no choice condition compared to the free choice condition (p = 0.002). For sugar snaps and baby corn, the intake was comparable in both conditions, and there were no significant differences. When comparing intake at these visits across the entire sample (using Mann-Whitney U tests), similar levels were found: Snack carrot (73.2 ± 4.2, n = 65 vs 65.5 ± 4.4, n = 46), sugar snaps (26.5 ± 3.3, n = 66 vs 42.8 ± 9.4, n = 12), and baby corn (36.4 ± 4.5, n = 65 vs 36.7 ± 10.7, n = 9). No significant differences were found between conditions, but carrot intake tended to be highest in the no choice condition (p = 0.09), while sugar snaps intake tended to be highest in the free choice condition (p = 0.06). Comparable findings were found when comparing the adjusted intake in the no choice conditions (visit 2–4) to the intake in the free choice condition with a mix of vegetables with three alternatives (visit 7) (using Wilcoxon signed rank tests). The mean intake of carrots was significantly higher in the no choice condition compared to the free choice mixture option (36.4 ± 2.5 vs 32.4 ± 2.6, n = 46, p = 0.05). For sugar snaps (16.4 ± 3.1 vs 16.1 ± 2.7, n = 24) and baby corn (15.8 ± 4.1 vs 12 ± 3.2, n = 22), there were no significant differences by choice condition.
3. Results 3.1. Participant characteristics The study included 86 children aged 2–6 years (50 boys and 36 girls). The characteristics of the children are shown in Table 2. 3.2. Familiarity and liking For the dummy stimuli, cucumber was familiar and liked (100%, Table 2 Description of participants. Child Characteristics Sex Male Female
% (N) 58 (50) 42 (36)
Age Child age in months
Mean ± SD 49 ± 11
3.4. Comparison of total vegetable intake The mean total vegetable intake was significantly higher (p = 0.04) in the free choice condition (visit 6, 57.5 ± 4) compared to the no choice conditions with single stimuli and three choice alternatives (visit 174
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have included in a vegetable subscription service, 86% preferred 3 or more different types (Olsen et al., 2012). However, children can only eat a very limited amount and are not typically served a wide range of options, which would also result in food waste, so a few options may be the best trade-off, but that remains to be determined experimentally. Fifth, the children were rather young (2–6 years) and may lack the cognitive development to fully understand the distinct choice options. Children in the pre-operational stage (2–7 years) do not have the ability to use logical reasoning (Piaget, 1964) and therefore choice manipulation may be more effective in older children or adolescents (de Wild et al., 2015; Warren, Parry, Lynch, & Murphy, 2008). In addition, young children are not necessarily used to having a free choice and may not appreciate this option, which could explain the significant age effect in the no choice condition. Although it has previously been shown that choice offering may enhance intrinsic motivation in children (Patall, Cooper, & Robinson, 2008; Ryan & Deci, 2000), followed by experience of autonomy and facilitation of greater overall vegetable intake (DeCosta et al., 2017), this might only be the case for children of older age. It is also possible that, in young children, choice offering may have positive effects on qualitative parameters only (e.g. appreciation), which were thus not measurable in this study using intake as a quantitative outcome parameter. Sixth, study setting and consumption context can determine children’s food choices. Studies conducted in natural settings have found a positive effect on choice in 4–6-year olds (Rohlfs Domínguez et al., 2013). A strength of this study was its setting in the nursery that was familiar to the children and where they were regularly offered vegetables as an afternoon snack. Zeinstra. Koelen, et al. (2010a), Zeinstra, Renes, et al. (2010) investigated the effect of choice-offering in a restaurant setting, where children were more excited about the restaurant setting than expected, which may have biased the effect of choice offering. It would be useful to compare different settings (e.g. home, day care, school, dining out/restaurant). Seventh, choice offering may work best in combination with certain other approaches to changing children’s eating behavior, possibly nudging and choice architecture, which may be useful tools to encourage healthy choices in children by providing an environment that influences food choices just by its design (Thaler, Sunstein, & Balz, 2014). It is worth commenting upon the low vegetable intake on the day with bonfire pancakes. These data clearly demonstrate that children are interested in eating snack vegetables in general, but to a much lesser extent if they know that more palatable foods are available. This is important knowledge when designing future choice alternatives. Finally, strengths which should be mentioned to supplement the above, are the assessment of intake of each individual vegetable type for each child at each visit, the individually conducted hedonic evaluations, and the use of snack vegetables that were familiar and wellliked. Limitations include the order of the visits; it may have been better to fully randomize visits, instead of having choice visits before no choice visits. The sample size was comparable to other studies, but as there were always some children absent at the visits, findings may have been more robust with a larger sample with more power. Also, the children were all from the same nursery, which was located in an urban area, so results may not extrapolate to children in more rural areas. Although children were instructed not to comment upon their food, they were not able to completely follow this instruction due to their young age, which means that some peer influence did occur. In conclusion, choice offering did not have a positive influence on vegetable consumption in 2–6 year-old pre-school children. Future studies should reveal whether this finding is linked to children’s age, setting, or choice of target stimuli, and whether there may be positive effects on more qualitative outcome parameters.
2–4 combined, 45.6 ± 3.1), which did not differ significantly from the free choice condition with a mix of two stimuli and three choice alternatives (visit 7, 48.2 ± 3.1). When comparing the two free choice conditions, children consumed more vegetables when eating their choice of vegetables as a single stimuli (57.5 ± 4) compared to the option with a mix of two stimuli (48.2 ± 3.1), but the difference was not significant. Age was shown to positively affect total mean vegetable intake in the no choice conditions (visit 2–4, p = 0.01), demonstrating that with increasing age children increased their mean total vegetable intake. No gender effects were found on the total vegetable intake. Results from the no choice condition with mix of stimuli (visit 5, n = 62, 27.1 ± 2.6) were excluded from any statistical analysis as the nursery teachers unintendedly changed the study setting that day (they made bonfire pancakes, which the children could see throughout the vegetable visit, and which they would receive right after they finished their vegetable serving, so most children were less interested in the vegetable servings that day). 4. Discussion The current study demonstrated none or even negative effects of offering pre-school children a free choice of snack vegetables when looking at stimuli-specific comparisons of intake (Fig. 1). However, choice offering had a positive effect when comparing the total vegetable intake across conditions with a single stimulus, but not with a mix of two stimuli. These somewhat contradictory results contribute to the mixed findings in previous choice studies in children, and there are several possible explanations to both the present finding and the fact that this seems to be an area with conflicting findings. First, the differences between the two types of analyses may be partly explained by a difference in the number of children participating in the analyses. In the direct comparisons (Fig. 1) only children attending both sessions are included, and only few children chose sugar snaps and baby corn when given a free choice with a single stimulus (visit 6), making these comparisons less robust. Accordingly, the positive effects of choice on overall intake seem to be caused by a relatively high intake of sugar snaps among a small group of children in the choice condition. Thus, this finding seems closely linked to stimulus type. From the results, it is also clear that intake within choice conditions varies considerably across the three stimuli types. This implies that stimuli-specific comparisons may more directly reflect the influence of choice per se, and may thus be more reliable than comparisons across different stimuli. Second, although the serving size was constant across visits (100 g), the amount of the different types of vegetables varied at visit 5–7 with mixed stimuli. It is possible that this may have influenced children’s perception of portion size or perceived variety – both parameters that have been shown to influence intake (Bergamaschi et al., 2016; Fisher, Arreola, Birch, & Rolls, 2007). Third, the selection of stimuli could affect how many vegetables that are consumed (Zeinstra, Koelen, Kok, & de Graaf, 2010). The present study investigated the intake of three raw vegetables, namely snack carrots, sugar snaps and baby corn, which only represent a limited range of vegetables typically consumed by children. As most studies have worked with specific choice sets it is questionable whether findings are solely due to the choice settings or to the specific vegetables included in the studies (i.e. factors linked to liking and familiarity of these). It is also not clear whether there are some food categories (e.g. fruit, meat or dairy) where choice is more appreciated than others. Fourth, the number of choice options presented at a time may moderate effects of choice offering. In adults, this has indeed been shown (Iyengar, 2010). For instance, when choosing among jams, a small selection was proven to be more effective than a wide selection among adult consumers when it comes to subsequent purchases and product satisfaction (Iyengar & Lepper, 2000). When 9–12 year old children were asked about how many vegetables they would like to 175
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Acknowledgements
of a good thing? Journal of Personality and Social Psychology, 79, 995–1006. Olsen, A., Ritz, C., Kramer, L., & Møller, P. (2012). Serving styles of raw snack vegetables. What do children want? Appetite, 59, 556–562. Patall, E. A., Cooper, H., & Robinson, J. C. (2008). The effects of choice on intrinsic motivation and related outcomes: A meta-analysis of research findings. Psychological Bulletin, 134, 270–300. Piaget, J. (1964). Part I: Cognitive development in children: Piaget development and learning. Journal of Research in Science Teaching, 2, 176–186. Roe, L. S., Meengs, J. S., Birch, L. L., & Rolls, B. J. (2013). Serving a variety of vegetables and fruit as a snack increased intake in preschool children. The American Journal of Clinical Nutrition, 98, 693–699. Rohlfs Domínguez, P., Gámiz, F., Gil, M., Moreno, H., Márquez Zamora, R., Gallo, M., & de Brugada, I. (2013). Providing choice increases children’s vegetable intake. Food Quality and Preference, 30, 108–113. Ryan, R. M., & Deci, E. L. (2000). Self-determination theory and the facilitation of intrinsic motivation, social development, and well-being. The American Psychologist, 55, 68–78. Thaler, R. H., Sunstein, C. R., & Balz, J. P. (2014). Choice architecture. SSRN Electronic Journal. https://doi.org/10.2139/ssrn.2536504. Véronneau, M., Koestner, R. F., & Abela, J. R. Z. (2005). Intrinsic need satisfaction and well-being in children and adolescents: An application of the self-determination theory. Journal of Social and Clinical Psychology, 24, 280–292. Warren, E., Parry, O., Lynch, R., & Murphy, S. (2008). “If I don’t like it then I can choose what I want”: Welsh school children’s accounts of preference for and control over food choice. Health Promotion International, 23, 144–151. WHO (2015). Promoting fruit and vegetable consumption around the world. Retrieved February 14, 2018, fromhttp://www.who.int/dietphysicalactivity/fruit/en/index2. html. Yngve, A., Wolf, A., Poortvliet, E., Elmadfa, I., Brug, J., Ehrenblad, B., ... Klepp, K.-I. (2005). Fruit and vegetable intake in a sample of 11-year-old children in 9 European countries: The pro children cross-sectional survey. Annals of Nutrition & Metabolism, 49, 236–245. Zeinstra, G. G., Koelen, M. A., Kok, F. J., & de Graaf, C. (2010a). The influence of preparation method on children’s liking for vegetables. Food Quality and Preference, 21, 906–914. Zeinstra, G. G., Renes, R. J., Koelen, M. A., Kok, F. J., & de Graaf, C. (2010b). Offering choice and its effect on Dutch children’s liking and consumption of vegetables: A randomized controlled trial. The American Journal of Clinical Nutrition, 91, 349–356.
The study was funded by the European Community’s Seventh Framework Programme (FP7/2007-2013) under the Grant Agreement No. FP7-245012-HabEat. The research received supplementary funding from the Taste for Life project, which is financed by the Nordea Foundation. The authors report no conflicts of interest. Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.foodqual.2018.10.011. References Bergamaschi, V., Olsen, A., Laureati, M., Zangenberg, S., Pagliarini, E., & Bredie, W. L. P. (2016). Variety in snack servings as determinant for acceptance in school children. Appetite. Chen, A. W., Resurreccion, A. V. A., & Paguio, L. P. (1995). Age appropriate hedonic scales to measure food preferences of young children. Journal of Sensory Studies, 11(1996), 141–163. Cooke, L. (2007). The importance of exposure for healthy eating in childhood: A review. Journal of Human Nutrition and Dietetics, 20, 294–301. de Wild, V. W. T., de Graaf, C., Boshuizen, H. C., & Jager, G. (2015). Influence of choice on vegetable intake in children: An in-home study. Appetite, 91, 1–6. DeCosta, P., Møller, P., Frøst, M. B., & Olsen, A. (2017). Changing children’s eating behaviour – A review of experimental research. Appetite, 113, 327–357. Dennison, B. A., Rockwell, H. L., & Baker, S. L. (1998). Fruit and vegetable intake in young children. Journal of the American College of Nutrition, 17, 371–378. Fisher, J. O., Arreola, A., Birch, L. L., & Rolls, B. J. (2007). Portion size effects on daily energy intake in low-income Hispanic and African American children and their mothers. The American Journal of Clinical Nutrition. Iyengar, S. (2010). The art of choosing. Art of Choosing, 1–6. Iyengar, S., & Lepper, M. (2000). When choice is demotivating: Can one desire too much
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