Caregivers' perspectives on the in-home implementation and effectiveness of “Miffy eats the rainbow!”: a colorful, modeling- and reward-based intervention to improve fruit and vegetable intake in children

Background: Home-based interventions can support fruit and vegetable (FV) consumption in young children. Although their effectiveness is well documented, real-life implementation experiences remain understudied; such knowledge is crucial for sustained and scalable impact. Citizen science offers a promising approach for collecting large-scale, practice-based insights into how such interventions are used in daily life. Objective: This study used a contributory citizen science approach to explore caregivers' experiences with the in-home implementation of "Miffy eats the rainbow!" and their perceptions of its effectiveness in supporting children's FV acceptance at home. Methods: A total of 42,000 sticker sheets were distributed across 420 Dutch retail locations, supported by a national media campaign. Caregivers who used the method at least once were invited to complete an online questionnaire assessing implementation outcomes (acceptability, appropriateness, feasibility, sustainability) and perceived effects on children's FV enjoyment, variety, and amount. Quantitative data were analyzed using descriptive statistics and ANOVA (by food fussiness); qualitative responses were thematically analyzed using an inductive approach. Results: A total of 209 caregivers participated (response rate: 0.5%). Implementation experiences were rated positively, with over 90% agreeing the method was fun (4.5 ± 0.6), easy to use (4.4 ± 0.7), and time efficient (4.3 ± 0.7). Ratings remained consistently high across all food fussiness levels. Perceived effects on children's FV enjoyment, amount, and variety were slightly positive, with mean scores ranging from 3.2 ± 1.0 to 3.6 ± 1.0. Qualitative responses provided additional insights into benefits, implementation strategies, and barriers. Conclusions: "Miffy eats the rainbow!" was positively received by self-selected caregivers, with high implementation ratings suggesting potential for broader in-home application. However, the very low response rate highlights challenges in achieving voluntary participation and raises concerns about selection bias. Future efforts should aim to promote inclusive engagement and evaluate long-term use across more diverse populations.