Children are not consuming sufficient amounts of fruits and vegetables in their habitual diet. Methods derived from associative learning theories could be effective at promoting vegetable intake in pre-school children. The objective of the present study was to compare the effectiveness of different learning strategies in promoting the intake of a novel vegetable. Children aged between 9 and 38 months were recruited from UK nurseries. The children (n72) were randomly assigned to one of three conditions (repeated exposure, flavour–flavour learning or flavour–nutrient learning). Each child was offered ten exposures to their respective version of a novel vegetable (artichoke). Pre- and post-intervention measures of artichoke purée and carrot purée (control vegetable) intake were taken. At pre-intervention, carrot intake was significantly higher than artichoke intake (P< 0·05). Intake of both vegetables increased over time (P< 0·001); however, when changes in intake were investigated, artichoke intake increased significantly more than carrot intake (P< 0·001). Artichoke intake increased to the same extent in all three conditions, and this effect was persistent up to 5 weeks post-intervention. Five exposures were sufficient to increase intake compared to the first exposure (P< 0·001). Repeated exposure to three variants of a novel vegetable was sufficient to increase intake of this vegetable, regardless of the addition of a familiar taste or energy. Repetition is therefore a critical factor for promoting novel vegetable intake in pre-school children.

The formation of new memories requires new information to be encoded in the face of proactive interference from the past. Two solutions have been proposed for hippocampal region CA1: (1) acetylcholine, released in novelty, selectively suppresses excitatory projections to CA1 from CA3 (mediating the products of retrieval), while sparing entorhinal inputs (mediating novel sensory information) and (2) encoding preferentially occurs at the pyramidal-layer theta peak, coincident with input from entorhinal cortex, and retrieval occurs at the trough, coincident with input from CA3, consistent with theta phase-dependent synaptic plasticity. We examined three predictions of these models: (1) in novel environments, the preferred theta phase of CA1 place cell firing should shift closer to the CA1 pyramidal-layer theta peak, shifting the encoding-retrieval balance toward encoding; (2) the encoding-related shift in novel environments should be disrupted by cholinergic antagonism; and (3) in familiar environments, cholinergic antagonism should shift the preferred theta firing phase closer to the theta trough, shifting the encoding-retrieval balance even further toward retrieval. We tested these predictions by recording from CA1 pyramidal cells in freely moving rats as they foraged in open field environments under the influence of scopolamine (an amnestic cholinergic antagonist) or vehicle (saline). Results confirmed all three predictions, supporting both the theta phase and cholinergic models of encoding versus retrieval dynamics. Also consistent with cholinergic enhancement of encoding, scopolamine attenuated the formation of distinct spatial representations in a new environment, reducing the extent of place cell “remapping.”

Most children do not meet daily recommendations for fruit and vegetable intake, and consumption of vegetables remains especially low. Eating habits track from childhood to adulthood hence establishing liking and intake of vegetables is important. To identify the most successful strategies to enhance vegetable intake in preschool children aged 2-5 years. The research was a systematic review and a meta-analysis of published studies. A comprehensive search strategy was performed using key databases such as Medline, Embase, PsychINFO, EBSCO and CENTRAL. Articles published between 2005-January 2016, specifically with measured vegetable consumption were included. 30 articles and 44 intervention arms were identified for inclusion (n = 4017). Nine dominant intervention strategies emerged to promote vegetable intake in preschool children. These included; choice, pairing (stealth), education, food service, modelling, reward, taste exposure, variety and visual presentation. The meta-analysis revealed that interventions implementing repeated taste exposure had better pooled effects than those which did not. Intake increased with number of taste exposures and intake was greater when vegetables offered were in their plain form rather than paired with a flavor, dip or added energy (e.g. oil). Moreover, intake of vegetables which were unfamiliar/disliked increased more than those which were familiar/liked. Repeated taste exposure is a simple technique that could be implemented in childcare settings and at home by parents. Health policy could specifically target the use of novel and disliked vegetables in childcare settings with emphasis on a minimum 8-10 exposures. The systematic review protocol was registered on the PROSPERO (number: CRD42016033984).

Vegetable intake is generally low among children, who appear to be especially fussy during the pre-school years. Repeated exposure is known to enhance intake of a novel vegetable in early life but individual differences in response to familiarisation have emerged from recent studies. In order to understand the factors which predict different responses to repeated exposure, data from the same experiment conducted in three groups of children from three countries (n = 332) aged 4–38 m (18.9±9.9 m) were combined and modelled. During the intervention period each child was given between 5 and 10 exposures to a novel vegetable (artichoke puree) in one of three versions (basic, sweet or added energy). Intake of basic artichoke puree was measured both before and after the exposure period. Overall, younger children consumed more artichoke than older children. Four distinct patterns of eating behaviour during the exposure period were defined. Most children were “learners” (40%) who increased intake over time. 21% consumed more than 75% of what was offered each time and were labelled “plate-clearers”. 16% were considered “non-eaters” eating less than 10 g by the 5^th exposure and the remainder were classified as “others” (23%) since their pattern was highly variable. Age was a significant predictor of eating pattern, with older pre-school children more likely to be non-eaters. Plate-clearers had higher enjoyment of food and lower satiety responsiveness than non-eaters who scored highest on food fussiness. Children in the added energy condition showed the smallest change in intake over time, compared to those in the basic or sweetened artichoke condition. Clearly whilst repeated exposure familiarises children with a novel food, alternative strategies that focus on encouraging initial tastes of the target food might be needed for the fussier and older pre-school children.

Purpose of Review The present review was undertaken in order to summarize and evaluate recent research investigating taste exposure, sensory learning, and nutrition education interventions for promoting vegetable intake in preschool children. Recent Findings Overall, taste exposure interventions yielded the best outcomes for increasing vegetable intake in early childhood. Evidence from sensory learning strategies such as visual exposure and experiential learning also show some success. While nutrition education remains the most common approach used in preschool settings, additional elements are needed to strengthen the educational program for increasing vegetable intake. There is a substantial gap in the evidence base to promote vegetable intake in food fussy children. Summary The present review reveals the relative importance of different intervention strategies for promoting vegetable intake. To strengthen intervention effects for improving vegetable intake in preschool children, future research could consider integrating taste exposure and sensory learning strategies with nutrition education within the preschool curriculum.