Repeated exposure and associative conditioning promote preschool children's liking of vegetables

The Impact of School Gardening on Cree Children's Knowledge and Attitudes toward Vegetables and Fruit

PURPOSE

School-based interventions may increase children's preferences for vegetables and fruit (V&F). This Canadian study measured changes in Indigenous First Nations schoolchildren's V&F knowledge, preferences, and home consumption following the implementation of a gardening and V&F snack program.

METHODS

At baseline, 7 months, and 18 months, children in grades 1-6 (i) listed at least 5 V&F they knew, (ii) tasted and indicated their preferences towards 9 vegetables and 8 fruit using a 6-point Likert scale, and (iii) indicated their home consumption of 17 V&F.

RESULTS

At all 3 time points, 56.8% (n = 66/116) of children provided data. Children listed a greater number of V&F at 18 months (4.9 ± 0.1) than at baseline (4.5 ± 1.0) or 7 months (4.7 ± .07) (F(1.6,105.6) = 6.225, P < 0.05). Vegetable preferences became more positive between baseline (37.9 ± 9.3) and 7 months (39.9 ± 9.2), but returned to baseline levels at 18 months (37.3 ± 8.7) (F(1.6,105.8) = 4.581, P < 0.05). Fruit preferences at 18 months (42.7 ± 3.0) were greater than at baseline (41.1 ± 4.3) and at 7 months (41.9 ± 5.1) (F(1.7,113.3) = 3.409, P < 0.05). No change in V&F consumption occurred at home.

CONCLUSIONS

Despite improvements in V&F knowledge and preferences, home consumption of V&F did not occur. Complementing school-based programs with home-based components may be needed to influence V&F intake of children.

Enjoyment of tactile play is associated with lower food neophobia in preschool children

Previous research has shown that parental reports of food neophobia and tactile sensitivity are associated with lower fruit and vegetable (F/V) intake in children. This study aimed to pilot a behavioral observation measure of tactile play in young children. The primary aim of the study was to see whether children's enjoyment of tactile play was associated with higher F/V consumption, as well as lower food neophobia. Seventy 2- to 5-year-old children (37 males and 33 females) and their parents were recruited through children's centers in the Leicester region of the United Kingdom during July to October 2012. Children's engagement in two tactile play tasks using sticky foods (mashed potatoes and vegetarian gelatin) was observed and rated by both the researcher and parent. Parents were asked to complete a series of questionnaires measuring F/V consumption, food neophobia, and sensory processing. It was found that lower child food neophobia was significantly related to enjoyment of tactile play, whereas child F/V consumption was associated with parental F/V consumption, but not enjoyment of tactile play. The findings strengthen the idea that tactile processing may be associated with the acceptance of food variety, but not the total amount of F/V consumed. Additional research is indicated to determine whether tactile play tasks can be used to lower child food neophobia.

Design and methodology of the LA Sprouts nutrition, cooking and gardening program for Latino youth: A randomized controlled intervention

OBJECTIVE

The LA Sprouts 12-week nutrition, cooking and gardening intervention targets obesity reduction in Latino children. While other gardening and nutrition programs are shown to improve dietary intake, LA Sprouts is unique in that it utilized a curriculum demonstrated to decrease obesity. This methodology paper outlines the design and processes of the LA Sprouts study, and discusses key strategies employed to foster successful implementation of the program.

SETTING

After-school program in four Los Angeles elementary schools.

SUBJECTS

3rd-5th grade students.

DESIGN

Randomized controlled trial. Gardens were built on two of four school campuses, and the 90-minute weekly lessons focused on strategies to increase fruit and vegetable consumption, gardening at school and home, and cooking healthy meals/snacks. Data collection was conducted pre- and post-intervention and included basic clinical and anthropometric measures, dietary intake and psychosocial constructs measured by questionnaire, and an optional fasting blood draw.

RESULTS

Baseline data was collected from 364 children, and 320 (88%) completed follow-up. No participants withdrew from the program (data were missing for other reasons). Intervention students attended 9.7 ± 2.3 lessons. Fasting blood samples were collected on 169 children at baseline, and 113 (67%) at follow-up. Questionnaire scales had good internal consistency (IC) and intra-rater reliability (IRR; in child scales: 88% items with IC > 0.7 and 70% items with IRR > 0.50; in parent scales: 75% items with IC > 0.7).

CONCLUSIONS

The intervention was successfully implemented in the schools and scales appear appropriate to evaluate psychosocial constructs relevant to a gardening intervention.

Serving first in isolation increases vegetable intake among elementary schoolchildren

Many people want to eat healthier, but they often fail in these attempts. We report two field studies in an elementary school cafeteria that each demonstrate children eat more of a vegetable (carrots, broccoli) when we provide it first in isolation versus alongside other more preferred foods. We propose this healthy first approach succeeds by triggering one’s inherent motivation to eat a single food placed in front of them, and works even though they have prior knowledge of the full menu available and no real time constraints. Consistent with this theory, and counter to simple contrast effects, an additional lab study found that presenting a food first in isolation had the unique ability to increase intake whether the food was healthy (carrots) or less healthy (M&M’s). Our findings demonstrate the effectiveness of this simple intervention in promoting healthier eating, which should interest consumers, food marketers, health professionals, and policy makers.

Twin studies advance the understanding of gene–environment interplay in human nutrigenomics

Investigations into the genetic architecture of diet–disease relationships are particularly relevant today with the global epidemic of obesity and chronic disease. Twin studies have demonstrated that genetic makeup plays a significant role in a multitude of dietary phenotypes such as energy and macronutrient intakes, dietary patterns, and specific food group intakes. Besides estimating heritability of dietary assessment, twins provide a naturally unique, case–control experiment. Due to their shared upbringing, matched genes and sex (in the case of monozygotic (MZ) twin pairs), and age, twins provide many advantages over classic epidemiological approaches. Future genetic epidemiological studies could benefit from the twin approach particularly where defining what is ‘normal’ is problematic due to the high inter-individual variability underlying metabolism. Here, we discuss the use of twins to generate heritability estimates of food intake phenotypes. We then highlight the value of discordant MZ pairs to further nutrition research through discovery and validation of biomarkers of intake and health status in collaboration with cutting-edge omics technologies.

Food Away from Home and Childhood Obesity

Childhood obesity is associated with a number of serious health risks that can persist into adulthood. While trends in food away from home and fast-food consumption have paralleled trends in childhood obesity, it is important to identify whether this is a causal relationship. This paper reviews recent literature in this area to summarize if there is a consensus in research findings. We group the literature into two areas - consumption of and access to food away from home (FAFH). While no consensus findings have been reached in either area, the evidence of an association between FAFH consumption and childhood obesity has gained strength. Further, there is evidence that FAFH meals add calories to children's diets. The literature on the role of FAFH access and childhood obesity has continued producing mixed results.

A step-by-step introduction to vegetables at the beginning of complementary feeding. The effects of early and repeated exposure

Breastfeeding (BF) is associated with willingness to accept vegetables. This may be due to the variety of flavours delivered via breast milk. Some mothers add vegetables to milk during complementary feeding (CF) to enhance acceptance. The present study tested a step-by-step exposure to vegetables in milk then rice during CF, on intake and liking of vegetables. Just before CF, enrolled mothers were randomised to an intervention (IG, n = 18; 6 BF) or control group (CG, n = 18; 6 BF). IG infants received 12 daily exposures to vegetable puree added to milk (days 1-12), then 12 × 2 daily exposures to vegetable puree added to rice at home (days 13-24). Plain milk and rice were given to CG. Then both received 11 daily exposures to vegetable puree. Intake was weighed and liking rated on days 25-26 and 33-35 after the start of CF in the laboratory, supplemented by the same data recorded at home. Vegetables were rotated daily (carrots, green beans, spinach, broccoli). Intake, liking and pace of eating were greater for IG than CG infants. Intake and liking of carrots were greater than green beans. However, at 6m then 18m follow up, vegetable (carrot > green beans) but not group differences were observed. Mothers reported appreciation of the structure and guidance of this systematic approach. Early exposure to vegetables in a step-by-step method could be included in CF guidelines and longer term benefits assessed by extending the exposure period.

Farm to elementary school programming increases access to fruits and vegetables and increases their consumption among those with low intake

OBJECTIVE

To assess the effectiveness of Wisconsin Farm to School (F2S) programs in increasing students' fruit and vegetable (FV) intake.

DESIGN

Quasi-experimental baseline and follow-up assessments: knowledge and attitudes survey, food frequency questionnaire (FFQ), and lunch tray photo observation.

SETTING

Wisconsin elementary schools: 1 urban and 8 rural.

PARTICIPANTS

Children, grades 3-5 (n = 1,117; 53% male, 19% non-Caucasian).

INTERVENTION(S)

Farm to School programming ranging from Harvest of the Month alone to comprehensive, including school garden, locally sourced produce in school meals, and classroom lessons.

MAIN OUTCOME MEASURES

Knowledge, attitudes, exposure, liking, willingness; FFQ-derived (total), and photo-derived school lunch FV intake.

ANALYSIS

t tests and mixed modeling to assess baseline differences and academic-year change.

RESULTS

Higher willingness to try FV (+1%; P < .001) and knowledge of nutrition/agriculture (+1%; P < .001) (n = 888), and lunch FV availability (+6% to 17%; P ≤ .001) (n = 4,451 trays), both with increasing prior F2S program exposure and across the year. There was no effect on overall dietary patterns (FFQ; n = 305) but FV consumption increased among those with the lowest intakes (FFQ, baseline very low fruit intake, +135%, P < .001; photos: percentage of trays with no FV consumption for continuing programs decreased 3% to 10%, P ≤ .05).

CONCLUSIONS AND IMPLICATIONS

Farm to School programming improved mediators of FV consumption and decreased the proportion of children with unfavorable FV behaviors at school lunch. Longer-term data are needed to further assess F2S programs.

Learning to eat vegetables in early life: the role of timing, age and individual eating traits

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.

The root of the problem: increasing root vegetable intake in preschool children by repeated exposure and flavour flavour learning

Children's vegetable consumption falls below current recommendations, highlighting the need to identify strategies that can successfully promote intake. The current study aimed to investigate the effectiveness of flavour-flavour learning as one such strategy for increasing vegetable intake in preschool children. Children (N = 29) aged 15 to 56 months were recruited through participating nurseries. Each received a minimum of six and maximium eight exposures to a root vegetable puree with added apple puree (flavour-flavour learning) alternating with six to eight exposures to another with nothing added (repeated exposure). A third puree acted as a control. Pre- and post-intervention intake measures of the three purees with nothing added were taken to assess change in intake. Follow-up measures took place 1 month (n = 28) and 6 months (n = 10) post-intervention. Intake increased significantly from pre- to post-intervention for all purees (~36 g), with no effect of condition. Magnitude of change was smaller in the control condition. Analysis of follow-up data showed that intake remained significantly higher than baseline 1 month (p < 0.001) and 6 months (p < 0.001) post-intervention for all conditions. Children under 24 months ate consistently more across the intervention than the older children (≥24 m) with no differences found in response to condition. This study confirms previous observations that repeated exposure increases intake of a novel vegetable in young children. Results also suggest that mere exposure (to the food, the experimenters, the procedure) can generalise to other, similar vegetables but the addition of a familiar flavour confers no added advantage above mere exposure.

Association between home availability and vegetable consumption in youth: a review

Objective

To systematically review literature examining the association between vegetable home availability and vegetable intake in youth.

Design

Articles were identified through December 2012 using a search of PubMed, PsychINFO and OVID/Medline databases, using the following keywords in varying combinations: home, environment, availability, vegetable, intake, consumption, children. Quantitative studies examining home vegetable availability and vegetable intake in children and adolescents were included. Fifteen studies were included that met inclusion criteria.

Setting

Studies were conducted in the USA (n 8), Australia (n 1), Greece (n 1), Iceland (n 1), Denmark (n 1), the UK (n 1), the Netherlands (n 1) and a combination of nine European countries (n 1).

Subjects

Various populations of children and adolescents were examined.

Results

Seven of the studies (47 %) found a positive association between vegetable availability and intake, with the others reporting null findings. There were no clear patterns of association by study design, age of subjects included, comprehensiveness of measures, or inclusion of covariates in analyses. Child report of home availability was associated with child vegetable intake (n 6, all found a positive association), while parent report of home availability was only minimally associated (n 9, one found a positive association; P=0·001 from post hoc Fisher’s exact test comparing parent v. child report).

Conclusions

Parent perception of availability may be closer to truth, given the parental role in food shopping and preparation. Therefore, to impact child vegetable intake, absolute availability may not be as important as child perception of vegetables in the home. Child perception of availability may be altered by level of familiarity with vegetables.

Learning to eat: birth to age 2 y

During the first 2 y of life, development is rapid and includes dramatic changes in eating behavior. Individual patterns of food preferences and eating behaviors emerge and differ depending on the foods offered and on the contexts of feeding during this early period of dietary transition. In this review, we discuss evidence on ways in which early learning influences food preferences and eating behavior, which, in turn, shape differences in dietary patterns, growth, and health. Although the evidence reviewed indicates that this early period of transition provides opportunities to influence children's developing intake patterns, there is no consistent, evidence-based guidance for caregivers who are feeding infants and toddlers; the current Dietary Guidelines are intended to apply to Americans over the age of 2 y. At present, the evidence base with regard to how and what children learn about food and eating behavior during these first years is limited. Before developing guidance for parents and caregivers, more scholarship and research is necessary to understand how infants and toddlers develop the food preferences and self-regulatory processes necessary to promote healthy growth, particularly in today's environment. By the time they reach 2 y of age, children have essentially completed the transition to "table foods" and are consuming diets similar to those of other family members. This article discusses parenting and feeding approaches that may facilitate or impede the development of self-regulation of intake and the acceptance of a variety of foods and flavors necessary for a healthy diet. We review the limited evidence on how traditional feeding practices, familiarization, associative learning, and observational learning affect the development of eating behavior in the context of the current food environment. Areas for future research that could inform the development of anticipatory guidance for parents and caregivers responsible for the care and feeding of young children are identified.

A review of visual cues associated with food on food acceptance and consumption

Several sensory cues affect food intake including appearance, taste, odor, texture, temperature, and flavor. Although taste is an important factor regulating food intake, in most cases, the first sensory contact with food is through the eyes. Few studies have examined the effects of the appearance of a food portion on food acceptance and consumption. The purpose of this review is to identify the various visual factors associated with food such as proximity, visibility, color, variety, portion size, height, shape, number, volume, and the surface area and their effects on food acceptance and consumption. We suggest some ways that visual cues can be used to increase fruit and vegetable intake in children and decrease excessive food intake in adults. In addition, we discuss the need for future studies that can further establish the relationship between several unexplored visual dimensions of food (specifically shape, number, size, and surface area) and food intake.

Early influences on the development of food preferences

The ability to perceive flavors begins in utero with the development and early functioning of the gustatory and olfactory systems. Because both amniotic fluid and breast milk contain molecules derived from the mother's diet, learning about flavors in foods begins in the womb and during early infancy. This early experience serves as the foundation for the continuing development of food preferences across the lifespan, and is shaped by the interplay of biological, social, and environmental factors. Shortly after birth, young infants show characteristic taste preferences: sweet and umami elicit positive responses; bitter and sour elicit negative responses. These taste preferences may reflect a biological drive towards foods that are calorie- and protein-dense and an aversion to foods that are poisonous or toxic. Early likes and dislikes are influenced by these innate preferences, but are also modifiable. Repeated exposure to novel or disliked foods that occurs in a positive, supportive environment may promote the acceptance of and eventually a preference for those foods. Alternatively, children who are pressured to eat certain foods may show decreased preference for those foods later on. With increasing age, the influence of a number of factors, such as peers and food availability, continue to mold food preferences and eating behaviors.

Serving a variety of vegetables and fruit as a snack increased intake in preschool children

BACKGROUND

Although serving a greater variety of food increases intake, this effect has not been well studied as a strategy to encourage consumption of vegetables and fruit in preschool children.

OBJECTIVE

This study examined whether providing a variety of familiar vegetables or fruit to preschool children as a snack would lead to increased selection and intake.

DESIGN

In a crossover design, 61 children (aged 3-5 y) ate a snack in their childcare facility on 8 afternoons. At 4 snack times, the children were offered vegetables: either a single type (cucumber, sweet pepper, or tomato) or a variety of all 3 types. At 4 other snack times, the children were offered fruit (apple, peach, pineapple, or all 3 types). Uniform-sized pieces were served family style, and children selected and ate as much as they desired.

RESULTS

Offering a variety of vegetables or fruit increased the likelihood of selection (P < 0.0001); children chose some pieces in 94% of snacks with variety and in 70% of snacks without variety. Serving a variety also increased consumption of both vegetables and fruit (P < 0.0002); the mean (±SEM) increase was 31 ± 5 g, about one-sixth the recommended daily amount. Independent of the variety effect, children were less likely to select vegetables than fruit (P < 0.0001), and the mean intake was substantially less for vegetables than for fruit (22 ± 1 compared with 84 ± 3 g).

CONCLUSIONS

Providing a variety of vegetables and fruit as a snack led to increased consumption of both food types in a childcare facility. Serving a variety of vegetables or fruit as a snack could help preschool children meet recommended intakes. This trial was registered at clinicaltrials.gov as NCT01557218.

Eating a rainbow. Introducing vegetables in the first years of life in 3 European countries

Low vegetable consumption in children is a concern in many EU countries, fewer than one fifth of children in Europe consume the WHO recommended amounts. Systematic studies demonstrate that experience with a variety of vegetables early in childhood can promote later consumption as early dietary habits often track into adulthood. This study examined pre-school children's experience with vegetables across three European countries in order to assess cultural differences, effects of age and culinary practices. Mothers of pre-school children (N=234) in the UK (N=71), Denmark (N=93) and France (N=70) completed a survey assessing parental and infant familiarity, frequency of offering and liking for 56 vegetables as well as preparation techniques for these vegetables. Analyses revealed that although children aged 25-36 months had been introduced to the greatest number of vegetables, children aged 6-12 months were offered vegetables more frequently and had a higher reported liking for these vegetables. UK children's liking was related to frequency of maternal intake and frequency of offering. Denmark had introduced the greatest number of vegetables and offered vegetables more frequently than both the UK and France. Choice of preparation methods differed between countries while choice of seasonings was similar. Results suggest increasing variety and frequency of vegetable offering between 6 and 12 months, when children are most receptive, may promote vegetable consumption in children.

Caffeine increases liking and consumption of novel-flavored yogurt

RATIONALE

Caffeine has been shown to increase preference for beverages with which it is paired; however, it is not known if caffeine alters liking for foods with which it is paired indirectly.

OBJECTIVES

The purpose of the current experiment was to test the hypothesis that a caffeinated beverage paired with a novel-flavored yogurt will increase preference for that yogurt compared to one paired with placebo. We also tested the hypothesis that liking would increase more when caffeine was paired with high energy density yogurt.

METHODS

Men and women (n = 62) were randomized to receive a beverage containing placebo (PLA) or caffeine (CAF) and to consume a low (LED) or high energy density (HED), novel-flavored yogurt. Participants rated, ranked, and consumed seven novel-flavored yogurts and then had a target yogurt paired with either PLA or CAF over four consecutive days.

RESULTS

In general, yogurt liking increased over time, the HED yogurt was liked more than the LED yogurt, and yogurt paired with caffeine was liked more than yogurt paired with placebo. Participants showed a significant increase in liking of LED yogurt paired with caffeine compared to those with LED yogurt paired with placebo.

CONCLUSIONS

Caffeine administration may increase liking and consumption of novel-flavored foods, particularly if the food is not highly liked at baseline. This suggests that caffeine pairing may be a way to increase liking of LED foods, such as vegetables and fruit.

Dimensions of vegetable parenting practices among preschoolers

The objective of this study was to determine the factor structure of 31 effective and ineffective vegetable parenting practices used by parents of preschool children based on three theoretically proposed factors: responsiveness, control and structure. The methods employed included both corrected item-total correlations and confirmatory factor analysis. Acceptable fit was obtained only when effective and ineffective parenting practices were analyzed separately. Among effective items the model included one second order factor (effectiveness) and the three proposed first order factors. The same structure was revealed among ineffective items, but required correlated paths be specified among items. A theoretically specified three factor structure was obtained among 31 vegetable parenting practice items, but likely to be effective and ineffective items had to be analyzed separately. Research is needed on how these parenting practices factors predict child vegetable intake.

Residential summer camp: a new venue for nutrition education and physical activity promotion

Background

Millions of children attend residential summer camps each year. However, few studies have examined the potential of camps for obesity prevention efforts. Research in the domain of positive youth development has shown that camp programs as short as one week have both short- and long-term positive effects on self-esteem, self-efficacy and other youth outcomes. The objective of the present study was to highlight the potential of resident camps as promising venues for the promotion of healthy eating and physical activity behaviors in the children who attend.

Methods

Data for this study came from the American Camp Association 2007 Emerging Issues Survey. This survey assessed camp professionals’ perspectives on a diverse array of issues, including the healthy eating and physical activity of children. Data analysis focused on responses from 247 camp professionals whose camps offered resident camp programs.

Results

Descriptive and Chi-square statistics were calculated. Ninety-two percent of camp professionals reported that the healthy eating and physical activity of campers was an “important” or “very important” issue for camps. The majority of camps reported offering vegetarian options, healthy snacks and salad bars, and allergen-free options. Additionally, 86% of camp professionals indicated that they had implemented one or more strategies to address concerns related to the unhealthy eating behaviors of children, with top strategies including increasing the availability of fruits and vegetables, increasing the availability of healthy drink options, and improving the nutritional quality of menus. Fewer camp professionals (50%) indicated they had implemented strategies to increase children’s physical activity levels, but many professionals indicated that their camp programs were inherently active and additional strategies to promote physical activity were not necessary. Associations were found between camp affiliation and food options available to campers.

Conclusions

The majority of camp professionals believe the healthy eating and physical activity of children are important issues for camps and have implemented strategies to address these issues. An important question for future research is to examine whether these strategies are effective in promoting healthy eating and physical activity behaviors in children, as well as ways that camp programs could be improved.

The addition of a plain or herb-flavored reduced-fat dip is associated with improved preschoolers' intake of vegetables

This quasiexperimental study used a within-subjects experimental design to determine whether adding herbs and/or spices to a reduced-fat dip increased children's willingness to taste, liking of, and consumption of vegetables. Participants were preschool children aged 3 to 5 years who attended a child-care center in Central Pennsylvania in late 2008 and early 2009. First, children's familiarity with and liking of six raw vegetables and five dips (reduced-fat plain, herb, garlic, pizza, and ranch) were assessed. In Experiment 1 (n=34), children tasted a vegetable they liked, one they disliked, and one they refused, with a reduced-fat plain dip and their favorite reduced-fat herb-flavored dip. In Experiment 2 (n=26 or n=27), they rated their liking of celery and yellow squash, with and without their favorite reduced-fat herb dip (pizza or ranch), and their intake of those vegetable snacks was measured. In Experiment 1, the herb-flavored dip was preferred over the plain dip (P<0.01), and children were three times more likely to reject the vegetable alone, compared with eating the vegetable paired with an herb dip (P<0.001). In Experiment 2, children ate significantly more of a previously rejected or disliked vegetable (celery and squash) when offered with a preferred reduced-fat herb dip than when the vegetable was served alone (P<0.05). These findings suggest that offering vegetables with reduced-fat dips containing familiar herb and spice flavors can increase tasting and thereby promote liking, acceptance, and consumption of vegetables, including vegetables previously rejected or disliked.

Masking Vegetable Bitterness to Improve Palatability Depends on Vegetable Type and Taste Phenotype

Consumption of dark green vegetables falls short of recommendations, in part, because of unpleasant bitterness. A laboratory-based study of 37 adults was used to determine bitter and hedonic responses to vegetables (asparagus, Brussels sprouts, kale) with bitter masking agents (1.33 M sodium acetate, 10 and 32 mM sodium chloride, and 3.2 mM aspartame) and then characterized by taste phenotype and vegetable liking. In repeated-measures ANOVA, aspartame was most effective at suppressing bitterness and improving hedonic responses for all sampled vegetables. Among the sodium salts, 32 mM sodium chloride decreased bitterness for kale and sodium acetate reduced bitterness across all vegetables with a tendency to increase liking for Brussels sprouts, as release from mixture suppression increased perceived sweetness. Participants were nearly equally divided into three 6-n-propylthiouracil (PROP) phenotype groups. Those tasting the least PROP bitterness (non-tasters) reported least vegetable bitterness, and the additives produced little change in vegetable liking. Aspartame persisted as the most effective bitter blocker for the PROP tasters (medium, supertasters), improving vegetable liking for the medium tasters but too much sweetness for supertasters. The sodium salts showed some bitter blocking for PROP tasters, particularly sodium acetate, without significant gains in vegetable liking. Via a survey, adults characterized as low vegetable likers reported greater increase in vegetable liking with the maskers than did vegetable likers. These results suggest that bitter masking agents (mainly sweeteners) can suppress bitterness to increase acceptance if they are matched to perceived vegetable bitterness or to self-reported vegetable disliking.

Repetition counts: repeated exposure increases intake of a novel vegetable in UK pre-school children compared to flavour–flavour and flavour–nutrient learning

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 (n 72) 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.

Influence of caffeine on the liking of novel-flavored soda in adolescents

BACKGROUND

Soda manufacturers claim that caffeine is added to soda as a flavor enhancer, but many researchers have speculated that caffeine is added to increase the hedonic and reinforcing properties of the soda. Studies in adults have demonstrated that caffeine can condition flavor preferences when added to novel-flavored beverages.

OBJECTIVES

The purpose of this study was to test the hypothesis that caffeine added to novel-flavored drinks would increase liking and preference in adolescents.

METHODS

Adolescents (n = 99) between the ages of 12 and 17 rated and ranked seven novel soda drinks. They were then randomly assigned to consume one of these beverages paired with either caffeine (1 or 2 mg/kg) or placebo over four consecutive days and rate liking. On the final visit, participants retasted the seven beverages and provided hedonic ratings and rankings.

RESULTS

Participants in the 2-mg/kg caffeine group increased the liking of the beverage over the exposure period after an initial decrease, but there was no change in liking for those in the placebo group or in the 1-mg/kg group. The increase in liking in the 2-mg/kg group was accompanied by a decrease in perceived bitterness, but no change in beverage ranking or consumption during the post-test.

CONCLUSIONS

Caffeine added to novel beverages results in a decrease in liking followed by an increase in liking with repeated exposures that may result from habituation to the bitterness of caffeine. Change in bitter perception may be the mechanism by which adolescents establish regular caffeine use.

Promoting children's healthy eating in obesogenic environments: Lessons learned from the rat

Current statistics on children's eating patterns and obesity rates are consistent with the idea that genetic taste predispositions, traditional feeding practices, and the obesogenic environment combine to increase the likelihood of unhealthy outcomes in many individuals. In this paper, we focus on one particular level of analysis through which this unhealthy combination of factors may begin to be disassembled: children's learning about food and flavors. Much of the research on children's learning about food and flavors has been inspired by the animal literature, which has a long history of carefully controlled studies elucidating the mechanisms through which rats and other animals learn to prefer and avoid foods and flavors. This literature provides many clues as to the processes by which learning paradigms may be used to encourage the intake of healthy foods, altering the implicit learning of obesogenic eating patterns that is likely to occur without intervention in the current environment. Overall, the implications of the literature are that children should be repeatedly exposed to a variety of flavors early in life, and that new flavors should be paired with already-liked flavors and positive contexts. This message is consistent with recent research results from our laboratory, showing that familiarization and associative learning paradigms may be used to increase young children's acceptance of, preference for, and intake of previously-unfamiliar, healthy foods.