Improving the school food environment and dietary intake of Dutch primary school students through the provision of a healthy school lunch: results of a pre-posttest effectiveness study

Background: This study aimed to improve the school food environment and dietary intake of Dutch primary school students by providing a healthy school lunch. We investigated (1) how the school lunch affected dietary intake and students’ preferences for the lunches and (2) whether compensation effects at home occurred. Methods: The study was conducted in Dutch primary schools among children in grades 5–8 (aged 8–12 years) and their parents. The intervention consisted of a free healthy school lunch for 6 months at three schools. To answer question 1, a quasi-experimental pre-post study was used. Lunch intake was assessed via photos at baseline, 3 and 6 months into the intervention, and 6 months after the intervention (12-month follow-up). Preferences were measured using a self-reported questionnaire at 3 and 6 months. To answer question 2, a quasi-experimental pre-post design with a comparison group (three intervention and three matched comparison schools) was used. Compensation effects, i.e., changes in home intake of healthy or unhealthy foods as a result of the school lunch, were assessed through a short parent questionnaire at month 6. Differences in consumption of core food groups were analyzed using non-parametric tests; compensation effects with Pearson chi-square tests. Results: A total of 312 children participated (55.4% female). At baseline, 7.2% of the children consumed vegetables during lunch, which increased significantly at 3 months to 56.1% and 50.6% at 6 months. The intake of whole-grain bread and water/milk also increased, while white bread and sugar-sweetened beverage intakes decreased. The lunch was well appreciated and did not lead to any substantial compensation effects at home. After the program ended, vegetable and whole-grain bread intake at school declined, while intake of white bread and sugary drinks increased to preintervention levels. Conclusions: Providing a healthy school lunch positively influenced children’s dietary intake at school without triggering unhealthy compensation at home. Improvements were most notable for vegetable intake, which increased substantially during the intervention. However, the effects were not sustained after the program ended, highlighting the importance of long-term provision and structural integration of healthy school lunches to support lasting dietary changes.