Background

Governments are increasingly focusing on the role that schools can play in improving children’s diet. One strategy is to restrict the availability of unhealthy options at meals and in school vending machines and tuck shops. Many schools also have policies regarding the types of foods that students are allowed to bring to school^{1, 2}. A complementary strategy is to increase the availability of healthy foods by improving the utritional standards of school meal options, providing free fruit, or offering only fruit and other healthy food choices in vending machines and tuck shops. In primary schools, fruit tuck shops and school policies are popular interventions since they require limited investment and are both relatively lowmaintenance and sustainable initiatives for schools³.

However, relatively little is known about the effectiveness of these and other school based actions to improve students’ diets. Simply making healthier food options more available may have little impact on students’ dietary behaviour. Students dietary choices may not change substantially unless choices are restricted, or their preferences are changed. Increasing healthy food availability may therefore be ineffective in the short run unless accompanied by restrictions on the availability of competing choices, while in the long run it is possible that such changes would eventually occur if preferences change due to factors such as peer influence and taste exposure.

Methods

The study was a cluster randomised trial among 43 primary schools in deprived areas in south Wales and south-west England. Throughout the study, both intervention and control schools were asked to continue with their existing curriculum and school meal arrangements. Intervention schools set up tuck shops that were not subsidised in any way. Schools were asked to offer a choice of fruit in the tuck shop at a fixed price and to not stock sweets, crisps or other such items. Schools were relatively free to choose how they operated the tuck shop and this resulted in a variety of different approaches³. Within the 43 participating schools, repeated cross-sections of children aged 9-11 completed a computerised 24-hour recall questionnaire at baseline (n=1902) and at one year follow-up (n=1924). The primary outcome measure was consumption of fruit and other sweet and savoury snacks, assessed using a single-day computerised 24-hour recall questionnaire completed by children. Previous research indicated that this measure showed acceptable levels of validity, reliability and sensitivity1. The questionnaire recorded the number of servings of 1) fruit, 2) sweets, chocolate, biscuits, and 3) crisps consumed during the previous 24-hour period. For each of these three food types, the number of servings consumed at school and throughout the whole day were calculated. Additional outcomes were collected at follow-up and assessed children’s preference for fruit and their peer group norms regarding fruit.

Results:

Approximately 70,000 fruits were sold over the year in the 23 intervention schools. This is the equivalent of 0.06 fruits per student per day, equivalent to 1 in 4 children eating 1 piece of fruit per week, or 1 in 17 eating fruit every day. Although children in intervention schools were more likely to report eating fruit as a snack at school ‘often’ compared to those in control schools (OR 1.49 (95% CI: 1.15, 1.95)), the dietary recall data did not indicate any significant differences in children’s intake of fruit or other snacks. However, there was a significant interaction (p<0.02) between intervention group and school food policy: where students were only allowed to bring fruit to school, fruit consumption was 0.37 portions per day (0.11, 0.64) higher in intervention schools, compared to 0.14 portions (-0.30, 0.58) where no food was allowed and 0.13 portions (-0.33, 0.07) where there were no restrictions.

Conclusions:

When introduced in isolation, fruit tuck shops had a limited impact on fruit consumption at school. However, when employed in conjunction with appropriate school policies, their impact was more significant, suggesting that when children and their friends are not allowed to bring unhealthy snacks to school, their willingness to use the fruit tuck shops and eat fruit as a snack in school is greatly enhanced. These results highlight the importance of supporting school health interventions with appropriate school policies and are consistent with socio-ecological models of behaviour change which support the value of mutually reinforcing multi-level comprehensive interventions^{4, 6}.