The Boost study: design of a school- and community-based randomised trial to promote fruit and vegetable consumption among teenagers

BACKGROUND: The aim of the Boost study was to produce a persistent increase in fruit and vegetable consumption among 13-year-olds. This paper describes the development, implementation and evaluation of a school-and community-based, multi-component intervention guided by theory, evidence, and best practice. METHODS/DESIGN: We used the Intervention Mapping protocol to guide the development of the intervention. Programme activities combined environmental and educational strategies and focused on increasing access to fruit and vegetables in three settings: School: Daily provision of free fruit and vegetables; a pleasant eating environment; classroom curricular activities; individually computer tailored messages; one-day-workshop for teachers. Families: school meeting; guided child-parent activities; newsletters. Local community: guided visits in grocery stores and local area as part of classroom curriculum; information sheets to sports-and youth clubs. The Boost study employed a cluster-randomised controlled study design and applied simple two-stage cluster sampling: A random sample of 10 municipalities followed by a random sample of 4 schools within each municipality (N = 40 schools). Schools were randomised into a total of 20 intervention-and 20 control schools. We included all year 7 pupils except those from school classes with special needs. Timeline: Baseline survey: August 2010. Delivery of intervention: September 2010-May 2011. First follow-up survey: May/June 2011. Second follow-up survey: May/June 2012. Primary outcome measures: Daily mean intake of fruit and vegetables and habitual fruit and vegetable intake measured by validated 24-hour recall-and food frequency questionnaires. Secondary outcome measures: determinants of fruit and vegetable intake, positive side-effects and unintended adverse effects. Implementation was monitored by thorough process evaluation. DISCUSSION: The baseline data file included 2,156 adolescents (95%). There was baseline equivalence between intervention-and control groups for sociodemographics, primary outcomes, and availability at home, school and sports-and youth clubs. Significantly larger proportions of pupils in the control group had parents born in Denmark. The study will provide insights into effective strategies to increase fruit and vegetable intake among teenagers. The study will gain knowledge on implementation processes, intervention effects in population subgroups with low intake, and opportunities for including local communities in interventions. TRIAL REGISTRATION: Current Controlled Trials ISRCTN11666034

The Boost study: design of a school- and community-based randomised trial to promote fruit and vegetable consumption among teenagers

Abstract Background The aim of the Boost study was to produce a persistent increase in fruit and vegetable consumption among 13-year-olds. This paper describes the development, implementation and evaluation of a school-and community-based, multi-component intervention guided by theory, evidence, and best practice. Methods/design We used the Intervention Mapping protocol to guide the development of the intervention. Programme activities combined environmental and educational strategies and focused on increasing access to fruit and vegetables in three settings: School: Daily provision of free fruit and vegetables; a pleasant eating environment; classroom curricular activities; individually computer tailored messages; one-day-workshop for teachers. Families: school meeting; guided child-parent activities; newsletters. Local community: guided visits in grocery stores and local area as part of classroom curriculum; information sheets to sports-and youth clubs. The Boost study employed a cluster-randomised controlled study design and applied simple two-stage cluster sampling: A random sample of 10 municipalities followed by a random sample of 4 schools within each municipality (N = 40 schools). Schools were randomised into a total of 20 intervention-and 20 control schools. We included all year 7 pupils except those from school classes with special needs. Timeline: Baseline survey: August 2010. Delivery of intervention: September 2010-May 2011. First follow-up survey: May/June 2011. Second follow-up survey: May/June 2012. Primary outcome measures: Daily mean intake of fruit and vegetables and habitual fruit and vegetable intake measured by validated 24-hour recall-and food frequency questionnaires. Secondary outcome measures: determinants of fruit and vegetable intake, positive side-effects and unintended adverse effects. Implementation was monitored by thorough process evaluation. Discussion The baseline data file included 2,156 adolescents (95%). There was baseline equivalence between intervention-and control groups for sociodemographics, primary outcomes, and availability at home, school and sports-and youth clubs. Significantly larger proportions of pupils in the control group had parents born in Denmark. The study will provide insights into effective strategies to increase fruit and vegetable intake among teenagers. The study will gain knowledge on implementation processes, intervention effects in population subgroups with low intake, and opportunities for including local communities in interventions. Trial registration Current Controlled Trials ISRCTN11666034.</p

Curricular activities and change in determinants of fruit and vegetable intake among adolescents: Results from the Boost intervention

Knowledge of the association between implementation of different intervention components and the determinants they are tailored to change may contribute to evaluating the effects and working mechanisms of multi-component interventions. This study examined 1) the effect of a Danish multi-component school-based intervention (2010−2011) on key determinants of adolescents' fruit and vegetable intake and 2) if dose of curricular activities was positively associated with change in these determinants. Using multi-level linear and logistic regression analyses stratified by gender and socioeconomic position, we analyzed survey data from the cluster-randomized Boost study targeting Danish 13-year-olds' fruit and vegetable intake. We examined 1) differences in knowledge of recommendations, taste preferences and situational norms between students from 20 intervention (n = 991) and 20 control (n = 915) schools at follow-up; and 2) associations between curriculum dose received and delivered (student and teacher data aggregated to school- and class-level) and these determinants among students at intervention schools only. At follow-up, more students from intervention than control schools knew the recommendation for vegetable intake (OR 1.56, CI:1.18, 2.06) and number of fruits liked (taste preferences) increased by 0.22 (CI:0.04, 0.41). At class-level, curriculum dose received was positively associated with proportion of students knowing the recommendation for vegetable intake (OR 1.06, CI:1.002, 1.13). In stratified analyses, this association was only significant among students from high social class (OR 1.17, CI:1.04, 1.31). The Boost intervention succeeded in improving students' taste preferences for fruit and knowledge of recommendation for vegetable intake, but only the latter determinant was positively associated with curriculum dose. Trial registration: ISRCTN1166603