Research ReportIncreasing children's acceptance of vegetables; a randomized trial of parent-led exposure
Introduction
There is considerable epidemiological evidence that the nutrients obtained from a diet high in fruit and vegetables can offer protection from cancer and cardiovascular disease (Hu et al., 2000, Joshipura et al., 2001, Liu et al., 2000, World Cancer Research Fund, 1997). Health promotion organizations worldwide broadly agree on a target of five portions of fruit and vegetables per day for good health. Adults' intake of fruit and vegetables remains substantially below recommended levels (Gregory et al., 1990, Li et al., 2000, Steinmetz and Potter, 1996, Thompson et al., 1999) and consumption in children appears to be even lower and may be declining (Gregory et al., 1995, Magarey et al., 2001).
There has been particular interest in increasing fruit and vegetable intake among young people, both because early intervention is likely to maximize health benefits (Perry et al., 1998a) and because eating habits in childhood are strongly predictive of those in adulthood (Cusatis et al., 2000, Kelder et al., 1994, Resnicow et al., 1998, Singer et al., 1995). The ‘5-a day’ program in the USA is a comprehensive and large-scale intervention, which includes a number of child-focused projects (Basch et al., 1994, Perry et al., 1998, Sorensen et al., 1999). The Maryland WIC 5-a-day Promotion Program (Havas et al., 1998) achieved a modest increase in fruit and vegetable consumption. The Child and Adolescent Trial for Cardiovascular Health (CATCH) included a more general healthy eating component and this failed to produce any significant improvements in fruit and vegetable intake (Perry et al., 1998a). One possible explanation for the limited impact of these campaigns is their focus on cognitive and practical barriers to eating behavior change. An alternative approach emphasizes hedonic factors. In studies with adults (Drewnowski, Henderson, Levine, & Hann, 1999) and children (Gibson et al., 1998, Gibson et al., 1998, Wardle, 1995), taste preferences have been shown to be highly predictive of actual intake, and parents often cite dislike as the primary explanation for children's low vegetable intake. If disliking represents an important barrier to consumption, then interventions aimed at modifying preferences could have an important part to play.
The acquisition of food preferences can be partly explained with reference to Rozin's (1976) concept of food ‘neophobia’ (literally ‘fear of the new’). As omnivores, humans show an interest in, but a reluctance to try, unfamiliar foods. Whilst neophobia might once have been adaptive, protecting the organism from dangerous foods, there is evidence to suggest that it may lead to less dietary variety and to nutritional inadequacies in children's diets at the present time (Falciglia, Couch, Gribble, Pabst, & Frank, 2000). In a recent survey of 2–6 year old children (Wardle, Gibson, Cooke, & Sapochnik, Further Reading) child neophobia was a highly significant predictor of low fruit and vegetable intake. Neophobia appears to reach a peak between the ages of 2 and 6 years (Pelchat and Pliner, 1995, Pliner, 1994, Pliner and Loewen, 1997) and rejection of vegetables in particular is common at this age (Beyer and Morris, 1974, Phillips and Kolasa, 1980). It has been suggested that dislike of cruciferous and leafy vegetables is an adaptation that deterred children from eating plants containing dangerous toxins at an age when they start to explore their environment more independently (Cashdan, 1998). The blandness and bitterness of such vegetables may also make them less acceptable to children who, are predisposed to prefer sweet tastes (Steiner, 1979). In addition, they are low in energy density which is increasingly viewed as an influence on acceptance (Gibson & Wardle, 2003).
A growing body of research suggests that a dislike of foods can be transformed into liking with experience of repeated tasting or ‘exposure’ (Kalat & Rozin, 1973). The efficacy of an exposure-based approach has been supported in experimental studies with infants (Birch et al., 1998, Gerrish and Mennella, 2001, Sullivan and Birch, 1994), pre-schoolers (Birch et al., 1987, Birch and Marlin, 1982, Sullivan and Birch, 1990) and schoolchildren (Loewen and Pliner, 1999, Pliner and Stallberg-White, 2000). In one study carried out in primary schools, 10 daily exposures to the taste of an unfamiliar vegetable (raw red pepper) significantly increased children's liking and consumption of the vegetable (Wardle, Herrera, Cooke, & Gibson, 2003). These results suggest that the exposure approach has promise for application in the real world, but it is still vital to demonstrate its effectiveness in the situation in which children's meals are actually eaten most of the time—i.e. served by parents in the home. Demonstrating that an exposure-based approach is effective when carried out by parents enhances the utility of the findings for modifying children's behavior in the real world.
The present study is a randomized controlled trial of the effectiveness of an exposure-based intervention, carried out by parents in the home, in increasing children's liking for a previously disliked vegetable. This represents a more ecological approach to changing children's eating habits than has previously been attempted. Parents of 2–6 year old children were assigned to one of three groups to receive either (a) training in ‘exposure’ feeding, (b) general nutritional information, or (c) no treatment. Participants in the latter two groups received the exposure training after the end of the intervention period. It was predicted that children receiving ten or more taste exposures would show an increase in liking and consumption of a previously disliked vegetable relative to either the information or control groups.
Section snippets
Participants
Participants were 156 children (87 boys and 69 girls) and their principal caregiver, who had taken part in a larger study (n=564) of predictors of children's fruit and vegetable intake and expressed an interest in participating in further research to modify their children's acceptance of vegetables. Thirteen children (one girl, 12 boys) were excluded when they didn't comply with the experimental procedures during the pre-intervention taste test. The remaining children (n=143) ranged in age from
Results
Three children (two in the Exposure group and one in the Control group) were withdrawn from the study by their parents after the pre-intervention taste test. Their data were not included. In addition, 14 participants in the Exposure group failed to complete a minimum of 10 out of 14 tasting sessions. Four children completed 9 sessions, two completed eight, two completed seven, one completed six and four completed five or less sessions. Given previous findings which suggest that a minimum of 10
Discussion
The results of the present study support the prediction that daily exposure to the taste of a previously disliked vegetable would increase children's liking and consumption of that vegetable relative to Information and Control conditions. This lends further weight to experimental evidence of the efficacy of repeated exposure in transforming rejection of new foods into acceptance in children of this age group (Birch et al., 1987, Birch and Marlin, 1982, Sullivan and Birch, 1990). Although highly
Acknowledgements
Supported by a research grant from Cancer Research UK (formerly The Cancer Research Campaign).
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