Time trends (1995–2008) in dietary habits among adolescents in relation to the Norwegian school fruit scheme: the HUNT study

INTRODUCTION: The importance of healthy eating in adolescence is well established. The present study examined possible effects of the free Norwegian School Fruit Scheme (NSFS), changes in dietary habits between 1995 and 2008, and whether secular changes in dietary habits differed among schools who implemented the NSFS during September 2007. METHOD: We used data from the Young-HUNT1 survey conducted from 1995 to 1997 and the Young-HUNT3 survey conducted from 2006 to 2008, which are part of the Nord-Trøndelag Health Study (HUNT), a longitudinal population health study. To evaluate the NSFS, the date Young-HUNT3 participants answered the questionnaire was used to identify affiliation to the intervention group (post-September 2007, n = 1892) or control group (pre-September 2007, n = 2855). To explore dietary habits over time, adolescents attending the same schools in Young-HUNT1 (n = 4137) and Young-HUNT3 (n = 4113) were included. Further, we investigated secular changes in dietary habits according to school type (intervention schools vs control schools). In all analysis, we explored possible differential effects according to socioeconomic status (SES) and gender. A questionnaire measured adolescents’ consumption of fruit, vegetables, candy, potato chips, sugar-sweetened beverages (SSB) and artificially sweetened beverages (ASB). Educational intention was used as a proxy for SES. Multilevel logistic regression was used. RESULTS: Within Young-HUNT3, the intervention group showed increased odds of daily consumption of fruit (aOR 1.7, 95% CI = 1.3–2.4) compared to the control group. Over time, adolescents were more likely to consume fruit (aOR = 1.48, 95% CI = 1.28–1.71), vegetables (OR = 1.41, 95% CI = 1.28–1.53), potato chips (aOR = 1.60, 95% CI = 1.26–2.04) and SSB (OR = 2.02, 95% CI = 1.66–2.45). Secular changes for fruit differed by school type: adolescents in intervention schools had higher odds of daily consumption (aOR = 1.82, 95% CI = 1.38–2.38) than those in control schools (aOR 1.26, 95% CI = 1.07–1.47). CONCLUSION: The results indicated that the NSFS increased adolescents’ fruit consumption. In the period assessed, the study identified positive and negative changes in adolescents’ dietary habits.