Study protocol: A cluster randomized trial to assess the effectiveness of comprehensive school meal nutrition standards on the diet quality of Cambodian schoolchildren (Version 2; May 2024)

Abstract Background: Poor diets compromise the health and physical and cognitive development of children. In Cambodia, schoolchildren’s diets are characterized by low intakes of fruits and legumes and high intakes of energy-dense, micronutrient poor snacks. Intakes of vitamin A, calcium and iron are also often below requirements. At present, the national school meal programme is being transitioned to full government ownership, presenting a unique opportunity to evaluate the effects of comprehensive school meal nutrition standards on the diet quality of Cambodian schoolchildren. Methods and analysis: Mixed-methods cluster randomized controlled trial with a closed cohort design. Forty schools, including 20 children per school, have been allocated 1:1 to control and intervention arms using a covariate constrained randomization. Schools allocated to intervention will provide school meals complying with the nutrition standards and a complementary food education package, while control schools will continue serving their regular school meals without modification. Dietary intake among schoolchildren will be assessed using quantitative 24-hour recalls, with a second non-consecutive recall among a subsample and weighed food records of the school meals. Baseline data were collected from March-June 2023 and endline data will be collected in August-September 2024. Primary outcomes are the intervention effect on usual intakes of fruits, vegetables, animal-source foods, and snack foods rich in salt, sugar and fat. Secondary outcomes include differences in usual energy, protein and micronutrient intakes and usual intakes of key food groups from the home diet across trial arms. Meal acceptability and implementation fidelity will also be assessed. Purposive sampling of schools will be employed for the qualitative assessment of implementation barriers and enablers in intervention schools. Mixed effects linear regression models will be fitted for the continuous outcomes, to estimate the mean difference across trial arms. Models will be adjusted for the baseline value of the outcome of interest and predictors, and include a random intercept for school. Discussion: This study will investigate if school meals compliant with comprehensive, context-specific nutrition standards have better results on diet quality than regular school meals that are planned based on budget constraints. The results of the trial can have implications on the review and uptake of the proposed nutrition standards at the national level. Trial registration: ISRCTN79659112. Registration date: 30 October 2023