Healthy Eating in Childhood: The Importance of Exposure
Children’s food preferences are strongly associated with their consumption patterns. Identifying factors that determine preferences is therefore crucial to the development of effective interventions to improve children’s diets. One of the most important determinants of a child’s liking for a particular food is the extent to which the food is familiar. In other words, children like what they know and they eat what they like.
The problem of neophobia
In theory, all a parent need do to ensure a healthy diet for their child is to provide a wide variety of nutritious foods and feed them often enough for those foods to become familiar. Unfortunately, a major barrier to increasing the familiarity of foods is a trait termed food neophobia (literally, ‘fear of the new’) that typically emerges during the second year of life. This manifests as an avoidance of, and reluctance to taste new foods and has been associated with poorer dietary quality and lower fruit and vegetable intake[4,5].
The effect of exposure
An extensive literature, both epidemiological and experimental, indicates that with experience of repeated tasting or “exposure”, neophobia can be reduced and dislikes transformed into likes. Surveys of food consumption and preferences have identified a link between early experience of tastes and subsequent food acceptance. For example, a cross-sectional survey of mothers of preschool children found that early introduction to fruits and vegetables during weaning was associated with increased intake in 2-6 year-olds . Likewise a longitudinal study in the US found that exposure to a wide variety of fruits in the first two years of life predicted variety of fruits consumed by school-aged children. Experimental studies have also provided evidence of the efficacy of exposure in increasing food preferences in animals as well as in human infants, preschoolers, and adults. The strength of the neophobic response changes during development as does the number of exposures required to effect change. In infants, a single exposure may be sufficient to dramatically increase intake and liking and effects may generalise to similar foods. Older children and adults on the other hand, may need as many as 10-15 taste exposures before benefits are observed. Laboratory-based research has also shown that there are circumstances in which exposure is less effective; for example, when the target food is intrinsically unpalatable or when exposure is in a different modality to that in which changes in preferences are being attempted, e.g. offering repeated visual exposure to food. Overall, however, the evidence clearly supports the use of taste exposure in healthy eating interventions.
In order to investigate whether the results of these studies can be replicated in real-world eating situations, we have carried out a series of more naturalistic studies aimed at increasing children’s acceptance of vegetables. Vegetables are an important target for intervention because children’s consumption is known to be inadequate and neophobia is specifically associated with lower intake. The first of these, a randomised, controlled trial in a school setting evaluated two interventions, one reward-based and one exposure-based. Children aged 5-7 were randomised to one of the intervention groups or to a no-treatment control after a preintervention session during which they tasted and rated pieces of red pepper (uncooked). Eight days of either simple tasting or tasting rewarded with a sticker followed for the two experimental groups, with no further intervention for the control group. Children in the exposure group’s liking and intake of the pepper increased significantly from pre- to post-intervention, as did that of the reward group, but to a smaller extent, suggesting that giving rewards may limit the impact of exposure.
In a second study of 2-6 year-olds, mothers randomised to an exposure condition were taught exposure feeding techniques and asked to offer their child a taste of an individually-selected, target vegetable every day for 14 days. Greater increases in liking, ranking and intake were observed in the exposure group when compared both with an information group given healthy eating leaflets or a no-treatment control group. Increases were significant only in the exposure group.
There is a need to test the effectiveness of this approach in more socio-economically disadvantaged populations among whom vegetable intake is known to be particularly low. We therefore undertook a pilot study to evaluate a similar exposure-based intervention delivered in a group setting to low income mothers and their two year old children (Cooke & Wardle, manuscript submitted). Significant increases in liking of and intake of a target vegetable were observed after two weeks of daily tasting. Mothers were very positive about the content and format of the intervention and about the value of the exposure techniques that they had been taught. A randomised controlled trial is now needed to replicate these findings in a larger sample with a longer term follow-up.
The power of “mere exposure” to alter children’s food preferences is well-established and experimental findings have begun to inform the content of interventions. If future large-scale interventions prove to be successful, simple advice could be offered to health professionals or to parents themselves.
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