title: The role of curriculum dose for the promotion of fruit and vegetable intake among adolescents: results from the Boost intervention.
abstract: BACKGROUND
  Multi-component interventions combining educational and environmental strategies have proved effective in increasing children and adolescents' fruit and vegetable intake. However such interventions are complex and difficult to implement and several studies report poor implementation. There is a need for knowledge on the role of dose for behaviour change and for assessment of intervention dose to avoid conclusions that intervention components which are not implemented are ineffective. This study aimed to examine 1) the association between dose of a class curriculum and adolescents' fruit and vegetable intake in a school-based multi-component intervention, 2) if gender and socioeconomic position modify this association.
  
  
  METHODS
  We carried out secondary analysis of data from intervention schools in the cluster-randomized Boost study targeting 13-year-olds' fruit and vegetable intake. Teacher- and student data on curriculum dose delivered and received were aggregated to the school-level and class-level (only possible for student data). We analysed the association between curriculum dose and students' (n 995) self-reported fruit and vegetable intake (24-h recall questionnaire) after finalization of the intervention using multi-level analyses. Potential moderation was examined by analyses stratified by gender and socioeconomic position.
  
  
  RESULTS
  Average dose received at class-level was significantly associated with students' fruit and vegetable intake (10 g (CI: 0.06, 20.33) per curricular activity received). In stratified analyses the association remained significant among boys only (14 g (CI: 2.84, 26.76) per curricular activity received). The average dose delivered and received at the school-level was not significantly associated with students' intake.
  
  
  CONCLUSIONS
  We found a dose-response relationship between number of curricular activities received and adolescents' fruit and vegetable intake. The results indicate that curriculum dose received only mattered for promotion of fruit and vegetable intake among boys. Future studies should explore this gender difference in larger samples to guide the planning of school-based curricular interventions with regards to the optimal number of curricular activities required to promote behavioural change in subgroups with low fruit and vegetable intake at baseline.
  
  
  BACKGROUND
  Current Controlled Trials ISRCTN11666034.
authors.affiliation: Centre for Intervention Research in Health Promotion and Disease Prevention, National Institute of Public Health, University of Southern Denmark, Øster Farimagsgade 5A, 2nd floor, Copenhagen, K, 1353, Denmark. thsj@niph.dk.
authors.forename: Thea Suldrup
authors.initials: TS
authors.lastname: Jørgensen
authors.affiliation: Centre for Intervention Research in Health Promotion and Disease Prevention, National Institute of Public Health, University of Southern Denmark, Øster Farimagsgade 5A, 2nd floor, Copenhagen, K, 1353, Denmark. mera@niph.dk.
authors.forename: Mette
authors.initials: M
authors.lastname: Rasmussen
authors.affiliation: Centre for Intervention Research in Health Promotion and Disease Prevention, National Institute of Public Health, University of Southern Denmark, Øster Farimagsgade 5A, 2nd floor, Copenhagen, K, 1353, Denmark. cl5k@suf.kk.dk.
authors.forename: Anne Kristine
authors.initials: AK
authors.lastname: Aarestrup
authors.affiliation: National Institute of Public Health, University of Southern Denmark, Øster Farimagsgade 5A, 2nd floor, Copenhagen, K, 1353, Denmark. ake@niph.dk.
authors.forename: Annette Kjær
authors.initials: AK
authors.lastname: Ersbøll
authors.affiliation: Centre for Intervention Research in Health Promotion and Disease Prevention, National Institute of Public Health, University of Southern Denmark, Øster Farimagsgade 5A, 2nd floor, Copenhagen, K, 1353, Denmark. saej@niph.dk.
authors.forename: Sanne Ellegaard
authors.initials: SE
authors.lastname: Jørgensen
authors.affiliation: Division of General Academic Pediatrics, Massachusetts General Hospital for Children, Massachusetts General Hospital, 55 Fruit Street, Boston, MA, 02114, USA. egoodman3@mgh.harvard.edu.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Goodman
authors.affiliation: National Institute of Public Health, University of Southern Denmark, Øster Farimagsgade 5A, 2nd floor, Copenhagen, K, 1353, Denmark. tppe@niph.dk.
authors.forename: Trine Pagh
authors.initials: TP
authors.lastname: Pedersen
authors.affiliation: Centre for Intervention Research in Health Promotion and Disease Prevention, National Institute of Public Health, University of Southern Denmark, Øster Farimagsgade 5A, 2nd floor, Copenhagen, K, 1353, Denmark. pdu@niph.dk.
authors.forename: Pernille
authors.initials: P
authors.lastname: Due
authors.affiliation: Centre for Intervention Research in Health Promotion and Disease Prevention, National Institute of Public Health, University of Southern Denmark, Øster Farimagsgade 5A, 2nd floor, Copenhagen, K, 1353, Denmark. rkr@niph.dk.
authors.forename: Rikke
authors.initials: R
authors.lastname: Krølner
mesh_terms: D000293:Adolescent; D002648:Child; D003479:Curriculum; D003718:Denmark; D004777:Environment; D005178:Faculty; D005247:Feeding Behavior; D005260:Female; D005421:Flavoring Agents; D005638:Fruit; D006293:Health Promotion / Q000379:methods*; D006801:Humans; D008297:Male; D012574:Schools; D013334:Students; D014675:Vegetables
chemical_list: D005421:Flavoring Agents