Healthy diet metrics for children and adolescents and their suitability for global monitoring: a critical review

Healthy diets during childhood and adolescence are paramount for growth, development, and long-term health. However, there is a lack of low-burden standardized metrics to assess and monitor healthy diets among children and adolescents aged 2-19 years of age on a global scale. This critical review aimed to identify and evaluate existing metrics for assessing healthy diets in this age group and to determine their suitability for global monitoring based on feasibility and adaptability across different contexts. A systematic search was conducted across three global databases, encompassing both peer-reviewed and grey literature. A total of 127 distinct healthy diet metrics were identified many of which were developed or adapted based on national dietary guidelines across various geographical contexts. Only five were deemed suitable for global monitoring due to their feasibility and adaptability: the Individual Dietary Diversity Score, 7 food group Minimum Dietary Diversity, 10 food group Minimum Dietary Diversity, Healthy Plate Variety Score, and Adapted ultra-processed food (UPF) Nova Score. Among these metrics, diversity was the most commonly measured sub-construct of a healthy diet, while only the Adapted Nova Score aimed to capture moderation. These five metrics were further evaluated for construct validity, reliability, and cross-context equivalence, which revealed large evidence gaps, particularly regarding sensitivity to change and test-retest reliability. These findings highlight the need for additional research to validate healthy diet metrics globally to ensure their accuracy, sensitivity, and reliability to differentiate populations and changes over time. Developing robust, low-burden metrics is essential for informing effective, timely nutrition policies and interventions aimed at improving the diets of children and adolescents worldwide.