Children and adolescents’ internalizing problems have been recognized as a public health challenge. There is growing interest in exploring how modifiable lifestyle interventions, such as dietary and nutritional intakes, may be effective in reducing the risk of internalizing problems. However, the adolescent population has received little attention in this regard. Prior studies have indicated that sleep problems and increased weight status, also significant public health concerns, are substantially associated with an increased risk of internalizing problems. Recent studies have highlighted the relationship between fish consumption and sleep and internalizing problems, as well as serum zinc levels related to body weight and internalizing issues. However, the intricacies of these relationships remain partially understood. In particular, the potential moderating effect of fish consumption on the association between sleep problems and internalizing problems, as well as the mediating effect of serum zinc levels on the relationship between weight status and internalizing problems, remains unexplored.The dissertation aims to investigate the effects of dietary intake and nutrition on internalizing problems among adolescents. Paper 1 is a systematic review that examines the current research on the relationship between dietary intake, food group consumption, dietary quality, serum micronutrient concentrations, and internalizing problems in adolescents. Papers 2 and 3 will use data from the China Jintan Child Cohort to explore the moderating effect of fish consumption and the mediating effect of zinc levels on the relationship between sleep, weight, and internalizing problems in early adolescents. Paper 2 aims to examine the association of fish intake and internalizing problems and to test whether fish consumption moderates the association between early and late sleep problems and internalizing problems (n=508). Paper 3 aims to investigate the partial mediating effect of serum zinc concentration on the relationship between weight status and internalizing problems (n=143). The findings of the proposed study have the potential to guide the development of future internalizing problem prevention strategies aimed at enhancing the well-being of adolescents.