Does the Royal Horticultural Society Campaign for School Gardening increase intake of fruit and vegetables in children? Results from two randomised controlled trials

Abstract

BACKGROUND Children’s fruit and vegetable intake in the UK is low. Changing intake is challenging. Gardening in schools might be a vehicle for facilitating fruit and vegetable intake. OBJECTIVES To undertake the first clustered randomised controlled trials (RCTs) of a gardening intervention. To evaluate the impact of a school gardening programme, the Royal Horticultural Society (RHS) Campaign for School Gardening, on children’s fruit and vegetable intake. METHODS Primary school children aged 8–11 years from eight London boroughs were included in one of two related RCTs. Trial 1 consisted of 23 schools, randomised to receive either a RHS-led or teacher-led intervention. Trial 2 consisted of 31 schools, randomised to either the teacher-led intervention or a comparison group. A 24-hour food diary [the Child And Diet Evaluation Tool (CADET)] collected baseline and follow-up dietary intake. Questionnaires measured children’s knowledge and attitudes towards fruit and vegetables and assessed intervention implementation. Data were collected by fieldworkers who were blind to the original allocation of the school. The primary outcome was change in fruit and vegetable intake analysed using a random effects model, based on intention to treat. RESULTS Total sample size at baseline for both trials (2529 children) was lower than the original aim of 2900 children. The final sample size was 1557, with 641 children completing trial 1 (RHS-led, n = 312; teacher-led, n = 329) and 916 children completing trial 2 (teacher-led, n = 488; control, n = 428). The response rate at follow-up for the two combined was 62%. Baseline analysis of children’s fruit and vegetable intake showed that eating a family meal together, cutting up fruit and vegetables, and parental modelling of fruit and vegetable intakes were all associated with higher intakes of fruit and vegetables in children. The primary trial outcome, combined fruit and vegetable intake, showed that in trial 1 the teacher-led group had a mean change in intake of 8 g [95% confidence interval (CI) –19 to 36 g], compared with a mean of –32 g (95% CI –60 to –3 g) in the RHS-led group. However, this difference was not significant (intervention effect –43 g, 95% CI –88 to 1 g; p = 0.06). In trial 2, the teacher-led group consumed 15 g (95% CI –36 to 148 g) more fruit and vegetables than the comparison group; this difference was not significant. No change was found in children’s knowledge and attitudes. However, if schools improved their RHS gardening score by three levels, children had a higher intake of 81 g of fruit and vegetables (95% CI 0 to 163 g; p = 0.05) compared with schools with no change in gardening score. CONCLUSION Results from these trials provide little evidence that school gardening alone can improve children’s fruit and vegetable intake. In both trials, gardening levels increased across all groups from baseline to follow-up, with no statistically significant difference between groups in terms of improvement in gardening level. This lack of differentiation between groups is likely to have influenced the primary outcome. However, when the gardening intervention was implemented at the highest intensities there was a suggestion that it could improve children’s fruit and vegetable intake by a portion. Analysis of the baseline data showed that family support for fruit and vegetable intakes was associated with higher intakes of fruit and vegetables in children. This study highlights the need for more sophisticated and accurate tools to evaluate diet in children. Future intervention designs should include a greater level of parental involvement in school interventions, along with related components such as cooking, to substantially improve children’s fruit and vegetable intake. In addition, the home environment has been demonstrated to be an important focus for intervention. TRIAL REGISTRATION Current Controlled Trials ISRCTN11396528. FUNDING This project was funded by the National Institute for Health Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 2, No. 4. See the NIHR Journals Library website for further project information.