Dietary patterns and neuropsychological function in adolescents: a cross-sectional and longitudinal study

BACKGROUND: Adolescence is a critical period for brain development, during which dietary patterns may influence neuropsychological functioning. OBJECTIVE: To examine cross-sectional associations and determine if baseline adherence to the Mediterranean diet (MD) and ultra-processed food (UPF) consumption is associated with changes in adolescent neuropsychological outcomes over 6 months. METHODS: This study represents a secondary analysis of the WALNUTs Smart-Snack Trial. We evaluated 653 adolescents (aged 12-16 years) from Barcelona at baseline and at 6-month follow-up. All dietary data used for these analyses were collected at the baseline timepoint only. MD adherence was measured with the KIDMED index and UPF consumption was assessed using a food frequency questionnaire and classified using the NOVA system. Cognitive domains were assessed at both time points using standardised computer-based tasks: attention (alerting, orienting, executive control) with the Attention Network Test; working memory (4-back) with the N-back task; fluid intelligence with the Primary Mental Abilities-Revised; decision-making with the Roulettes Task; and emotion recognition with the Emotion Recognition Task. Behavioural outcomes were also evaluated at both time points using the self-reported Strengths and Difficulties Questionnaire and teacher-reported Attention-Deficit/Hyperactivity Disorder-DSM-IV scales. Associations were examined using multivariable generalised linear models. To further validate UPF consumption estimations, polyphenol biomarkers were measured in urine in a subsample of 257 participants. RESULTS: Greater adherence to the MD was cross-sectionally linked to fewer behavioural problems and higher scores of executive functioning, while higher UPF consumption was associated with poorer emotion recognition, reduced alerting attention, less advantageous decision-making, more behavioural problems and internalising symptoms. Longitudinally, higher UPF consumption was associated with more internalising symptoms and less advantageous decision-making, whereas MD adherence showed no associations. CONCLUSIONS: Greater MD adherence appears associated with more favourable behavioural and cognitive profiles. In contrast, higher UPF consumption seems to be associated with less favourable profiles across multiple neuropsychological domains in adolescents. However, the limited longitudinal evidence points to complex relationships that warrant further investigation. Overall, these findings highlight the importance of promoting healthier dietary habits during adolescence.