Changes in Children’s Adherence to Sustainable Healthy Diets During the Implementation of Chile’s Food Labelling and Advertising Law: A Longitudinal Study (2016–2019)

<b>Objectives</b>: This longitudinal study measured changes in adherence to sustainable healthy diets in 698 Chilean children (aged 3-6 years at baseline) over the period that Chile's Food Labelling and Advertising Law was implemented. <b>Methods</b>: Dietary data were collected annually from 2016 to 2019 applying single multiple-pass 24 h dietary recalls to children's primary caretakers. The Planetary Health Diet Index for Children and Adolescents (PHDI-C) was used to quantify adherence to sustainable healthy diets where higher scores indicate better adherence. Linear mixed models were fitted to estimate the change in PHDI-C total and individual component scores from 2016 to 2019. <b>Results</b>: Mean total PHDI-C score decreased from 50.1 points in 2016 to 46.3 and 46.1 in 2018 and 2019, respectively (<i>p</i>-value < 0.001), suggesting that children's overall adherence to sustainable healthy diets was low and decreased over time. Intake of <i>legumes</i>, <i>fruits</i>, <i>dark green vegetables</i>, <i>red and orange vegetables</i>, and <i>vegetable oils</i> decreased, while intake of <i>palm oil</i>, <i>red meats</i>, and <i>animal fats</i> increased, resulting in small but significant declines in eight PHDI-C component scores. <i>Whole cereal</i> intake increased, while the consumption of <i>dairy products</i> and <i>added sugars</i> decreased, resulting in improvements in three PHDI-C component scores. <b>Conclusions</b>: Aside from the decrease in <i>added sugar</i> intake, all dietary changes observed in this study were consistent with trends described among children transitioning from pre-school age to school age. The Law might have contributed to reducing children's added sugar intake, but further research is required to establish causality.