Effect of diet on cognition, mental health and wellbeing among adolescents: a systematic review

A healthy diet is crucial for adolescents’ health and wellbeing. Current literature on dietary intake and its association with cognition, mental health and wellbeing has mainly focused on younger children. The aim of this systematic review was to explore the evidence for these associations in adolescents. Studies were included if they were full-text, peer-reviewed English-language publications that included only adolescents aged 10–19 years. Eligible studies explored the relationship between adolescent dietary intake (dietary patterns, dietary quality, or nutrient intakes) and validated measures of cognition, mental health, or wellbeing. Studies focusing solely on eating behaviours (e.g., skipping breakfast) or nutritional supplement interventions, and animal or laboratory/clinical setting studies were excluded. Ten electronic databases were searched; two independent reviewers screened all retrieved articles. Eligible studies published between 1/1/2000 and 7/10/2024 were searched. Study methodological quality was assessed independently by two reviewers using the Joanna Briggs Institute critical appraisal tools. A narrative synthesis was conducted. Fifty articles were included; five studies on cognition, 33 studies on mental health and 20 studies on wellbeing – some studies investigated both mental health and wellbeing outcomes. Forty-four cross-sectional and seven longitudinal studies were identified – one inclusion contained two separate studies. Mediterranean diet adherence was positively associated with higher cognitive performance, attention capacity, and learning processes. Healthier diets were generally associated with better mental health and a reduced risk of conditions such as depression and anxiety. A “Western” diet, characterised by a high intake of processed foods, sugars and saturated fats, was associated with poorer mental health. Higher overall diet quality was associated with better wellbeing across diverse populations. Unhealthy eating patterns and lower diet quality were associated with poorer wellbeing. Evidence suggests an association between higher-quality adolescent dietary intake and better cognition, mental health, and wellbeing. The predominant reliance on cross-sectional data precludes causal inferences and may indicate reverse causality (in which mental health symptoms drive poor dietary choices) or residual confounding. Future research requires more longitudinal and intervention studies to establish causal pathways, greater standardisation of dietary definitions and consistent controls for important confounders.