Intervention

The nutrition education curriculum used in the intervention was designed to improve children’s nutrition and health knowledge and preferences for fruits and vegetables. This intervention was grounded in Social Cognitive Theory^{( 22 )}, which emphasizes environmental inputs that contribute to children’s self-efficacy around dietary behaviours. As Bandura notes, from a social cognitive perspective, in order for school-based health promotion programmes to be effective, children must be equipped with the beliefs and skills needed to change their behaviours^{( 23 )}. Our curriculum provides children with age-appropriate background information on nutrition and health that is intended to change their belief systems around the benefits of eating healthy foods. Further, our curriculum gives children opportunities to develop the skills necessary to make healthy choices and try a variety of foods they may not have been exposed to before. Thus, our curriculum is in line with a Social Cognitive Theory approach.

The curriculum was developed during the summer of 2016 in collaboration with three 3rd grade teachers. Recruiting 3rd grade teachers was deliberate as we did not want to cut into our research pool of 2nd grade teachers, and 3rd grade teachers begin their teaching year with ‘ending’ 2nd grade students. Thus, they would understand the developmental stage of 2nd graders and be equipped to develop the curriculum. During a full-day workshop, the research team and teachers developed a 6-week curriculum, consisting of lessons implemented twice per week. The lessons were developed based on four existing programmes: MyPlate for grades 1–2 and 3–4, Two-Bite Club, and Put a Rainbow on Your Plate. As lessons were developed, they were aligned to the National Health Education Standards. This enabled teachers to cover topics required by the state while using the nutrition lessons. In addition to direct instruction on nutrition and health, a variety of age-appropriate activities were implemented throughout the programme including trivia, food tastings, projects and games.

Week 1 focused on the overarching questions, ‘What does it mean to be healthy?’ and ‘What does it mean to eat healthy?’ The MyPlate framework was highlighted. As a culminating activity for day 2, students labelled a blank copy of the MyPlate diagram after learning the components of healthy meals during both lessons of week 1. Week 2 emphasized the question, ‘Why is it important to eat a variety of foods from all food groups?’ The concept of nutrients was introduced and the book, Two-Bite Club, was read. The primary goal of the Two-Bite Club book is to encourage children to try at least ‘two bites’ of foods, and following this first reading children were challenged to try two bites of new foods as they were introduced throughout the rest of the nutrition curriculum. Week 3 focused on the questions, ‘What should I eat less of and why?’ and ‘What can I eat instead?’ This week was focused on teaching children strategies for replacing sweet or salty snacks with healthy choices. Week 3 also introduced the Put a Rainbow on Your Plate framework that was incorporated throughout the rest of the curriculum. Put a Rainbow on Your Plate encourages children to eat foods that are a variety of colours. In week 3, children learned the nutritional benefits of red foods while sampling a variety of red fruits and vegetables. Week 4 focused on the final question to be emphasized throughout the remainder of the programme: ‘Why should we eat fruits and vegetables?’ During this week, children learned the nutritional benefits of orange foods and sampled fruits and vegetables that are orange. The final project was also introduced to children this week. The final project served as an assessment of children’s understanding of key concepts introduced throughout the curriculum. The curriculum provided each class a choice from one of three projects: (i) children creating ‘Eat the Rainbow’ posters to be placed in the school cafeteria; (ii) children developing video commercials for various fruits and vegetables to be played on the school news; or (iii) children holding a farmers’ market (with pretend or real foods) to ‘sell’ to students in other grades or to school adults. Each project required children to report on the nutritional benefits of fruits and vegetables. Weeks 5 and 6 focused on the continuing theme of ‘Why should we eat fruits and vegetables?’ and emphasized the nutritional value and tasting of green and blue/purple foods, respectively. The final projects were presented in week 6.

Overall, intervention implementation fidelity was high. On average, over the course of 6 weeks, teachers reported delivering two lessons per week (mean 2·00 (sd 0·11)) that lasted approximately 15–20 min each, which was the targeted duration and dosage. Teachers also indicated that, on average, they implemented the lessons as intended (mean 3·65 (sd 0·42); 4-point scale). Finally, teachers reported that children were engaged in and enjoyed the lessons (mean 3·56 (sd 0·46) and mean 3·57 (sd 0·58), respectively; 4-point scale).